Evaluation of Mechanical Ventilation Modes in the Laparoscopic Perioperative Period with Electrical Impedance Tomography

Evaluation of Mechanical Ventilation Modes in the Laparoscopic Perioperative Period with Electrical Impedance Tomography | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Evaluation of Mechanical Ventilation Modes in the Laparoscopic Perioperative Period with Electrical Impedance Tomography Zhiwei Li, Yang Wu, Yao Yu, Kai Liu, Hang Tian, Jiafeng Yao, Qiuju Cheng This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5369936/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Purpose: The lung protective ventilation strategy has been advocated during the laparoscopic perioperative period. However, uncertainty remains as to which mode of mechanical ventilation is more appropriate in the laparoscopic perioperative period. We hypothesized the pressure controlled ventilation - volume guaranteed (PCV-VG) mode is a better option than the volume controlled ventilation (VCV) mode in the laparoscopic perioperative period. Method: The trial was a self-controlled study. The laparoscopic perioperative period is divided into five phases: before induction of anesthesia (AWAKE), after induction of anesthesia (BEGIN), the first phase of the surgery (MIDDLE-1), the second phase of the surgery (MIDDLE-2), and before postoperative wakefulness (END). The BEGIN phase and MIDDLE-1 phase use the VCV mode, and the MIDDLE-2 phase and END phase use the PCV-VG mode. EIT data are recorded at each phase and the parameters of EIT were calculated to quantify the performance of pulmonary ventilation in space and time. Results: During the non-surgical period, compared with VCV mode, PCV-VG mode had a significant increase in CoV (48.7 ± 2.6 vs. 47.0 ± 3.7, P < 0.01*), a significant decrease in RVDI (8.5 ± 3.1 vs. 10.1 ± 3.9) and no significant difference in GI (0.80 ± 0.10 vs. 0.77 ± 0.08, P = 0.067). During the surgical period, compared with VCV mode, PCV-VG mode had a significant increase in CoV (46.0 ± 3.6 vs. 42.5 ± 3.3, P < 0.001*), a significant decrease in GI (0.87 ± 0.15 vs. 1.03 ± 0.28; P < 0.01*) and a significant decrease in RVDI (11.1 ± 3.8 vs. 15.4 ± 5.1; P < 0.001*) Conclusion: EIT ventilation parameters between VCV mode and PCV-VG mode have significant differences in the laparoscopic perioperative period. The PCV-VG mode could improve ventilation inhomogeneity and elevated ventilation delay due to changes in position and pneumoperitoneum during surgery. The PCV-VG mode might be better used to meet the changing demands for ventilation at different surgical stages. We believe that PCV-VG is a more alternative during laparoscopic surgery. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1 Introduction Perioperative lung protective ventilation reduces the risk of postoperative pulmonary complications and improves lung function and prognosis[ 1 – 3 ]. Lung protective ventilation strategies aim to reduce potential lung injury from intraoperative mechanical ventilation by optimizing mechanical ventilation parameters[ 4 – 6 ]. During the perioperative period of laparoscopic anesthesia, changes in position and pneumoperitoneum lead to the development of pulmonary atelectasis in the area of dependence, increasing the risk of local lung injury[ 7 , 8 ]. Timely adaptation of lung-protective ventilation strategies in the laparoscopic perioperative period is necessary. The main parameters used to monitor lung function intraoperatively are respiratory compliance and oxygenation index (PaO 2 /FiO 2 ). However, evaluating the ventilatory status of the lungs using only these parameters is limited[ 9 , 10 ]. Electrical impedance tomography (EIT) is a non-invasive, dynamic, visual medical monitoring technique that has been demonstrated to be valuable in guiding lung protective ventilation strategy[ 11 – 14 ]. EIT provides information on impedance changes in the region of lung ventilation and allows the distribution of lung ventilation to be shown in the reconstructed images. In clinical anesthesia, EIT is mainly used to guide prone therapy, lung tidal volume monitoring, and pleural effusion detection[ 15 – 17 ]. In particular, EIT has shown significant advantages in finding optimal positive end-expiratory pressure (PEEP) and reducing localized lung collapse[ 18 – 20 ]. However, uncertainty remains as to which mode of mechanical ventilation is more conducive to lung protective ventilation in the laparoscopic perioperative period. For the most part, clinical experience and subjectivity dominate. The two modes of mechanical ventilation commonly used in anesthesia machines are volume-controlled ventilation (VCV) mode and pressure controlled ventilation - volume guaranteed (PCV-VG) mode. In VCV mode, the anesthesia machine delivers gas to the patient's lungs according to a set tidal volume (TV) and a fixed flow rate. PCV-VG mode is designed to ensure that the patients receive both a stable ventilation pressure and a set tidal volume during ventilation. In addition, in PCV-VG mode, the anesthetist adjusts the pressure of each breath to achieve a preset tidal volume based on real-time measurements of lung compliance and resistance. Most researchers had evaluated two modes of mechanical ventilation in terms of respiratory mechanics, but the studies still have limitations[ 21 , 22 ]. In this study, we evaluated the impacts of VCV mode and PCV-VG mode on lung ventilation in the perioperative laparoscopic period from spatial and temporal perspectives according to EIT ventilation parameters. Our primary goal was to determine which mode of mechanical ventilation is more conducive to lung-protective ventilation in anesthesia clinics and to provide a guideline for the subsequent use of EIT in clinical practice. 2 Materials and Methods 2.1 Experimental ethics The trial was approved by the Ethics Committee of Guangzhou Women and Children Medical Centre (Guangzhou, China; ID: Sui Women's and Children's Corun Tong Zi [2022] No. 292B00). The clinical registration number is ChiCTR2400089365. All participants signed informed consent before enrollment. Twenty-four cardiorespiratory sound female patients requiring laparoscopic surgery were included in the study. Laparoscopic surgery was mainly performed for benign tumors of the ovaries, uterine fibroids, and secondary infertility. The patients entered the operating theatre and were connected to a monitoring system (monitoring heart rate, blood pressure, and oxygen saturation). To more sensitively monitor the impedance signals, the EIT electrode belt was placed slightly below the breast, roughly between the 4th and 5th ribs[ 23 ]. Anesthesia was induced with remimazolam (0.3 mg/kg), sufentanil (0.3 µ g/kg), cisatracurium (0.3 mg/kg) and propofol (2 mg/kg). 2.2 Experimental procedure The trial procedure is shown in Fig. 1 . The laparoscopic perioperative period is divided into five phases. In the AWAKE phase, the patients are in the supine position, awake, and spontaneous breathing. Induction of anesthesia was followed by the BEGIN phase. The patients are in the supine position and intubated in VCV mode. Then enter the surgical period. In the MEDDLE 1 phase, the patients are in the recumbent position (head-down and feet-up position), pneumoperitoneum, and the VCV mode is maintained. In the MEDDLE 2 phase, the PCV-VG mode is used. In the END phase, at the end of the surgery, the patients return to the supine position and maintain the PCV-VG mode. PEEP in mechanical ventilation was set at 3–4 cmH 2 O and initial tidal volume was set at 6–8 ml/kg of weight. The respiratory rate was fixed at 12/min. Finally, the clinical data of 24 patients were statistically analyzed and targeted for screening. EIT data were collected using the EIT-1000 (Suzhou Jiantong Medical Technology Co., Ltd., Jiangsu, China). The output signal of the EIT measuring system is an AC = 1mA, 122kHz safety current. The EIT belt has 16 electrodes and the skin around the human chest is wiped with alcohol or saline before wearing to reduce the effects of contact impedance. Impedance tomography images were recorded at 20 fps with good and stable electrode contact. 2.3 Experimental program To ensure the validity of the data, EIT voltage data were recorded after the waveform stabilized at each phase, and the recording duration was more than 10 min. For the MIDDLE-2 phase, EIT data were recorded 15 min after the respiratory signal had stabilized, and for the remaining four phases the recording started 5 min after the respiratory signal had stabilized. The 15-minute transition time in MIDDLE-2 is set to eliminate the potential effects of the VCV mode in MIDDLE-1 on the PCV-VG mode in MIDDLE-2. The image reconstruction algorithm of EIT is Gaussian-Newton regularization and the smoothness of the image is enhanced by convolutional filtering[ 24 ]. The pixel size of each image is 128×128. 2.4 Experimental parameters Center of ventilation (CoV), global inhomogeneity (GI), and regional ventilation delay index (RVDI) are commonly used to quantify lung function in EIT[ 25 – 27 ]. EIT tidal image is obtained by calculating impedance changes between the end-inspiratory and end-expiratory moments in one respiratory cycle in Fig. 2 . Each pixel point in the image represents relative impedance changes in the chest. The parameters of EIT are obtained based on the EIT tidal images. The value of CoV higher than 50 indicates a larger proportion of dorsal ventilation. Conversely, the proportion of ventral ventilation is larger. This protocol is determined by the direction of the prescribed y-axis. GI reflects the homogeneity of pulmonary ventilation. Lower GI values indicate better consistency in the region of pulmonary ventilation. The value of RVDI reflects the delay in pulmonary ventilation. Lower GI values indicate less difference in ventilation times across regions of the lung. For the same patient, the EIT tidal images for the five phases were unified to the same color scale range and EIT ventilation parameters were calculated under the same contour. The averages of the EIT parameters for five consecutive respiratory cycles were taken for each phase. 2.5 Statistical Analysis The experimental subjects of this study were female patients requiring laparoscopic surgery. The primary purpose was to compare the clinical differences of two mechanical ventilation modes, VCV and PCV-VG. For statistical convenience, the phase of mechanical ventilation in the laparoscopic perioperative period was divided into the non-surgical and surgical periods. The non-surgical period includes the BEGIN phase and the END phase. The surgical period includes the MIDDLE-1 phase and the MIDDLE-2 phase. This experiment was a statistical study of clinical parameters under different phases during the perioperative laparoscopic period, and it was a self-controlled study. Statistical parameters covered heart rate, mean arterial pressure, end-tidal carbon dioxide, respiratory compliance, peak pressure, plateau pressure, driving pressure (ΔP), and oxygenation index (PaO 2 /FiO 2 ). The normal distribution of continuous variables was determined using the Shapiro-Wilk test. Results satisfying normality are expressed as mean ± SD, and the same variable was analyzed under two phases using paired t tests. Continuous variables that do not satisfy normality are expressed as medians (interquartile ranges) using Wilcoxon tests. Statistically significant values were considered to have P values less than 0.05. Statistical analyses were carried out using SPSS version 26.0. 3 Results A total of 24 patients underwent successful laparoscopic surgery with no adverse events or complications during the surgery. Four patients experienced prolonged poor electrode contact during the surgical period due to interference from surgical operation and environment noise. This part of the EIT data is considered invalid. So, we excluded the clinical data of these four patients and statistically analyzed the clinical data of the remaining 20 patients. Patient characteristics are shown in Table 1 . Two samples of EIT tidal images and RVDI distribution images in the perioperative period are shown in Fig. 3 . Table 1 Patient Characteristics Basic Parameters Laparoscopic surgery (N = 20) Age, median (IQR), year 37 (30–44) Height, mean ± SD, cm 157.7 ± 4.8 Weight, mean ± SD, kg 55.3 ± 12.1 Duration of surgery, mean ± SD, min 142.7 ± 63.1 Respiratory rate, median (IQR), per min 12 (10–14) The data are presented as the mean ± SD or median (IQR). Comparing the BEGIN phase and END phase (non-surgical period), ΔP was statistically significantly different and the remaining parameters were not significantly different (Table 2 ). Comparing the MIDDLE-1 phase and the MIDDLE-2 phase (surgical period), plateau pressure and ΔP were statistically significantly different and the remaining parameters were not significantly different. Comparing the BEGIN phase and the MIDDLE-1 phase (both in VCV mode), the heart rate was not significantly different and the rest of the parameters were statistically significantly different. Comparing the MIDDLE-1 phase and MIDDLE-2 phase (both in PCV-VG mode), the heart rate, end-tidal carbon dioxide and oxygenation index were not significantly different. The rest of the parameters were statistically significantly different. Table 2 Ventilation Parameters Laparoscopic surgery (N = 20) VCV mode PCV-VG mode P Value Heart rate (per min) Non-surgical period Surgical period P Value 66.7 ± 3.7 69.1 ± 2.8 0.354 * 70.0 ± 2.9 70.1 ± 2.3 0.968 * 0.359 * 0.274 * / Mean arterial pressure (mmHg) Non-surgical period Surgical period P Value 73.3 ± 2.2 84.0 ± 2.2 < 0.001* 77.1 ± 2.2 83.8 ± 2.0 0.004* 0.236 * 0.882 * / End-tidal carbon dioxide (mmHg) Non-surgical period Surgical period P Value 39.8 ± 1.3 43.0 ± 1.1 0.002* 42.3 ± 1.7 43.5 ± 1.4 0.028* 0.070* 0.064* / Compliance (mL/cmH 2 O) Non-surgical period Surgical period P Value 36.1 ± 1.4 24.4 ± 0.8 < 0.001* 38.6 ± 2.3 25.9 ± 0.9 < 0.001* 0.115* 0.105* / Peak pressure (cmH 2 O) Non-surgical period Surgical period P Value 13 (12–14) 18 (16–23) < 0.001 ₭ 13 (11–14) 17 (15–21) 0.002 ₭ 0.431 ₭ 0.059 ₭ / Plateau pressure (cmH 2 O) Non-surgical period Surgical period P Value 7 (6–8) 11 (9–13) < 0.001 ₭ 6 (5–7) 10 (8–11) < 0.001 ₭ 0.082 ₭ 0.009 ₭ / Driving pressure (cmH 2 O) Non-surgical period Surgical period P Value 4 (3–5) 8 (6–11) < 0.001 ₭ 3 (2–4) 7 (5–8) < 0.001 ₭ 0.017 ₭ 0.010 ₭ / PaO 2 /FiO 2 (mmHg) Non-surgical period Surgical period P Value 496 (452–668) 486 (433–540) 0.004 ₭ 500 (376–580) 468 (394–538) 0.281 ₭ 0.496 ₭ 0.376 ₭ / Measurements were taken at modes of mechanical ventilation (VCV and PCV-VG) during the surgery. The data are presented as the mean ± SD or median (IQR). Each group of data corresponds to its row and column. Non-surgical period and VCV mode = BEGIN. Surgical period and VCV mode = MIDDLE-1. Surgical period and PCV-VG mode = MIDDLE-2. Non-surgical period and PCV-VG mode = END. P values less than 0.05 are shown in bold. * is paired t test. ₭ is Wilcoxon test EIT tidal images of 20 patients in 5 phases were counted and the mean ventilation percentage was calculated for each region of interest (Table 3 ). The stacked histogram of the percentage of the average ventilation is shown in Fig. 4 . Intuitively, most of the ventilation regions are concentrated in the ROI2 and ROI3. The percentage of ventilation in the AWAKE phase is the baseline, with a 4% difference in the percentage of ventilation between ROI2 and ROI3. In the BEGIN phase, the ventilation percentage of ROI3 decreased by 8% compared to baseline, and the EIT image was shifted ventrally. In the MIDDLE-1 phase, the ventilation percentage of ROI3 reached 25.1%, a decrease of 21.2% compared to baseline. In the MIDDLE-2 phase, the ventilation percentage of ROI3 increased by 9.5% compared to the MIDDLE-1 phase, and the EIT image was shifted to the dorsal side. In the END phase, there was a 7.7% difference in the percentage of ventilation between ROI2 and ROI3, with more balanced ventral and dorsal ventilation. Table 3 Parameters of EIT AWAKE BEGIN MIDDLE-1 MEDDLE-2 END ROI 1 5 (3–7) 7 (5–9) 9 (7–13) 8 (5–10) 7 (5–8) ROI 2 43 (38–48) 54 (45–59) 64 (61–70) 55 (50–60) 50 (44–52) ROI 3 46 (40–52) 36 (31–47) 26 (18–34) 36 (26–40) 39 (36–47) ROI 4 6 (5–7) 2 (1–4) 1 (0–2) 3 (1–4) 4 (3–6) CoV 51.7 ± 2.9 47.0 ± 3.7 42.5 ± 3.3 46.0 ± 3.6 48.7 ± 2.6 GI 0.75 ± 0.06 0.80 ± 0.10 1.03 ± 0.28 0.87 ± 0.15 0.77 ± 0.08 RVDI 6.7 ± 2.1 10.1 ± 3.9 15.4 ± 5.1 11.1 ± 3.8 8.5 ± 3.1 ROI 1–ROI 4 are presented as median (IQR). CoV, GI and RVDI are expressed as mean ± SD. Region of interest ROI 1 is ventral, whereas ROI 4 is dorsal. AWAKE = before the induction of anesthesia; BEGIN = the beginning of anesthesia induction and VCV mode; MIDDLE-1 = the first phase of the surgery and VCV mode; MIDDLE-2 = the second phase of the surgery and PCV-VG mode; END = before postoperative wakefulness and PCV-VG mode; Pump, pneumoperitoneum operation. Box plots of the EIT parameters in the VCV and PCV-VG mechanical ventilation modes are shown in Fig. 5 . In the AWAKE phase, the mean value of CoV (51.4 ± 2.9) was higher than 50 (Table 3 ). For both the non-surgical period and the surgical period, CoV in PCV-VG mode was statistically significantly higher than in VCV mode (48.7 ± 2.6 vs. 47.0 ± 3.7, P < 0.01*; 46.0 ± 3.6 vs. 42.5 ± 3.3, P < 0.001*). RVDI in PCV-VG mode was statistically significantly lower than in VCV mode (8.5 ± 3.1 vs. 10.1 ± 3.9, P < 0.001*; 11.1 ± 3.8 vs. 15.4 ± 5.1; P < 0.001*). In the non-surgical period, GI was not significantly different between PCV-VG and VCV modes (0.80 ± 0.10 vs. 0.77 ± 0.08, P = 0.067). However, in the surgical period, GI was statistically significantly lower in PCV-VG mode than in VCV mode (0.87 ± 0.15 vs. 1.03 ± 0.28; P < 0.01*). In VCV mode, CoV decreased statistically significantly by 4.5 from the BEGIN phase to the MIDDLE-1 phase (P < 0.001*). GI increased statistically significantly by 0.23 (P < 0.001*). RVDI increased statistically significantly by 5.3 (P < 0.001*). In PCV-VG mode, CoV increased statistically significantly by 2.7 from the MIDDLE-2 phase to the END phase (P < 0.001*). GI decreased statistically significantly by 0.1 (P < 0.001*). RVDI decreased statistically significantly by 2.6 (P < 0.001*). In the non-surgical period, CoV in PCV-VG mode increased by 1.7, GI decreased by 0.03, and RVDI decreased by 1.6 compared to VCV mode. In the surgical period, CoV in PCV-VG mode increased by 3.5, GI decreased by 0.16, and RVDI decreased by 4.3 compared to VCV mode. 4 Discussion This trial compared the impacts of VCV and PCV-VG modes on pulmonary ventilation in the laparoscopic perioperative period. Lung ventilation status was quantified using EIT image parameters. The main findings were: (1) After induction of anesthesia, the patients were shifted from the supine position to the recumbent position and pneumoperitoneum was performed. The ventilation region of the EIT image was shifted ventrally, with decreased ventilatory coherence and increased ventilatory delay. (2) After surgery, the patients returned from the recumbent position to the supine position, and the pneumoperitoneum was released. The ventilation region of the EIT image was shifted dorsally, with increased ventilatory coherence and decreased ventilatory delay. (3) Both in the non-surgical and surgical periods, pulmonary ventilation in PCV-VG mode was more balanced in the ventral and dorsal regions, with a better performance of ventilatory coherence and lower ventilatory delay compared to the VCV mode. (4) PCV-VG mode contributes more to lung protective ventilation compared with VCV mode and reduces the impacts of poor ventilation due to changes in position and pneumoperitoneum during laparoscopic surgery. In the AWAKE phase, the patients were supine position and spontaneous breathing. CoV > 50 indicates a high percentage of dorsal ventilation. When the patients were mechanically ventilated after induction of anesthesia, CoV was mostly below 50, indicating that ventilation was concentrated in the ventral region. This clinical phenomenon is in line with previous research[ 28 ]. When spontaneous breathing, gravity dependence causes ventilation to be offset dorsally[ 29 ]. When mechanical ventilation is used, if a low PEEP is applied, it may lead to dorsal localized lung atelectasis and poor ventilation due to dorsal compression in the supine position[ 30 ]. From the BEGIN phase to the MIDDLE-1 phase, the region of lung ventilation is shifted ventrally. This result is similar to that in previous studies[ 31 ]. Decreased PaO 2 /FiO 2 implies that the alveolar ventilatory exchange function deteriorates. We further demonstrated that changes in position cause worse ventilation by the GI and RVDI parameters. Physiologically, the recumbent position (head-down and feet-up) and pneumoperitoneum cause the diaphragm to be forced up. The increased extent of compression on the dorsal side of the lungs results in dorsal alveolar collapse. Moreover, we found that ΔP increased and respiratory compliance decreased. It might be that the compression of the lungs causes airway resistance to increase, which leads to decreased pulmonary ventilation. From the MIDDLE-1 phase to the MIDDLE-2 phase, the region of lung ventilation is shifted dorsally. Compared with VCV mode, PCV-VG mode improved the uniformity of pulmonary ventilation distribution and reduced ventilation delay. It is noticed that a decreasing trend in plateau pressure and ΔP. The explanation for this phenomenon is that PCV-VG mode reduces airway resistance and improves respiratory compliance[ 32 ]. The alveolar collapse rate is reduced, ensuring effective ventilation of the lungs. Comparing the BEGIN and END phases also illustrates that PCV-VG mode is more conducive to pulmonary ventilation. From the MIDDLE-2 phase to the END phase, the patients were released from the pneumoperitoneum and returned to supine position with improved ventilation. It was further verified that changes in position and pneumoperitoneum cause abnormal pulmonary ventilation. In addition, we found that the extent of ventilation loss induced by the transition from the non-surgical period to the surgical period in VCV mode was higher than the extent of ventilation improvement induced by the transition from the surgical period to the non-surgical period in PCV-VG mode. This indirectly reflects the low sensitivity of PCV-VG mode to external disturbances and the ability to adjust the ventilation strategy more flexibly. When comparing the difference in mechanical ventilation modes between the non-surgical and surgical periods, we found that the improvement in pulmonary ventilation was more significant with PCV-VG mode than with VCV mode during the surgical period compared to the non-surgical period. In addition, GI was no significant difference between the two modes of mechanical ventilation during the non-surgical period. It is possible that pulmonary ventilation is less affected during the non-surgical period. There was little difference between the two modes of mechanical ventilation. When entering the surgical period, changes in position and pneumoperitoneum result in poor ventilation. At this point, PCV-VG mode is more helpful in alleviating poor ventilation. This also suggests that PCV-VG is a more alternative during laparoscopic surgery. The reason for using the before-after study in the same patient was considerations of individual pulmonary ventilation variability. We differ in that the ventilation contours and color bars of the EIT images of individuals under the five phases were harmonized, and all EIT parameters were calculated on a harmonized basis. We believe that EIT parameters calculated at the same level would be more valuable. However, this would also cause some statistical and order effects. Statistically, most of the clinical parameters were not statistically different between VCV and PCV-VG modes. Especially during the surgical period, although we analyzed the data after 15 min of changing PCV-VG mode, VCV mode of the previous phase could still potentially interfere with the ventilation parameters of PCV-VG mode. 5 Conclusion Significant differences in EIT ventilation parameters between VCV and PCV-VG modes were observed during the laparoscopic perioperative period. Compared with VCV mode, PCV-VG mode improves ventilation inhomogeneity and ventilation delay due to intraoperative position and pneumoperitoneum. PCV-VG mode automatically adjusts pressure and reduces airway resistance during surgery. In summary, PCV-VG is a much better choice in the laparoscopic stage of surgery. Declarations Funding Statement: Guangzhou Municipal Science and Technology Project under Grant 2023A03J0862. GuangDong Basic and Applied Basic Research Foundation under Grant 2022A1515220154. Conflicts of Interest: The authors declare no competing interests. Clinical Trial: Number: Sui Women's and Children's Corun Tong Zi [2022] No. 292B00. Ethics Committees: Ethics Committee of Guangzhou Women and Children Medical Centre. Date: 2022/05/09. Clinical Registration URL: ChiCTR2400089365. Author Contribution Zhiwei Li significantly contributed to the processing and analysis of EIT data associated with the work and drafting of the article and preparing Figure 3 - 5, Table 3.Yang Wu significantly contributed to EIT data analysis and preparing Table 1 - 2.Yao Yu significantly contributed to EIT data acquisition and preparing Figure 1 - 2.Kai Liu significantly contributed to the EIT system development and providing the article ideas.Hang Tian significantly contributed to the procedures for applying for ethical approval and the interpretation of data associated with the work.Jiafeng Yao significantly contributed to the interpretation of data associated with the work and reviewing the article.Qiuju Cheng contributed to the experimental design, the experimental execution, and providing the article ideas.All authors reviewed the manuscript. References Severgnini P, Selmo G, Lanza C, Chiesa A, Frigerio A, Bacuzzi A, et al. 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Influence of different electrode belt positions on electrical impedance tomography imaging of regional ventilation: a prospective observational study. CRIT CARE. 2016;20(1):3. Gómez-Laberge C, Adler A. Direct EIT Jacobian calculations for conductivity change and electrode movement. PHYSIOL MEAS. 2008;29(6):S89. Putensen C, Hentze B, Muenster S, Muders T. Electrical Impedance Tomography for Cardio-Pulmonary Monitoring. J CLIN MED. 2019;8(8):1176. Girrbach F, Petroff D, Schulz S, Hempel G, Lange M, Klotz C, et al. Individualised positive end-expiratory pressure guided by electrical impedance tomography for robot-assisted laparoscopic radical prostatectomy: a prospective, randomised controlled clinical trial. BJA. 2020;125(3):373–82. Van Oosten JP, Francovich JE, Somhorst P, van der Zee P, Endeman H, Gommers DAMPJ, et al. Flow-controlled ventilation decreases mechanical power in postoperative ICU patients. INTENS CARE MED EXP. 2024;12(1):30. Radke Oliver C, Schneider T, Heller Axel R, Koch T. Spontaneous Breathing during General Anesthesia Prevents the Ventral Redistribution of Ventilation as Detected by Electrical Impedance Tomography: A Randomized Trial. Anesthesiology. 2012;116(6):1227–34. Zitzmann A, Pulletz S, Gonzales-Rios P, Frenkel P, Teschendorf P, Kremeier P et al. (2023) Regional ventilation in spontaneously breathing COVID-19 patients during postural maneuvers assessed by electrical impedance tomography. 67(2):185–94. Bikker IG, Preis C, Egal M, Bakker J, Gommers D. Electrical impedance tomography measured at two thoracic levels can visualize the ventilation distribution changes at the bedside during a decremental positive end-expiratory lung pressure trial. CRIT CARE. 2011;15(4):R193. Ukere A, März A, Wodack KH, Trepte CJ, Haese A, Waldmann AD, et al. Perioperative assessment of regional ventilation during changing body positions and ventilation conditions by electrical impedance tomography. BJA. 2016;117(2):228–35. Schick V, Dusse F, Eckardt R, Kerkhoff S, Commotio S, Hinkelbein J et al. (2021) Comparison of Volume-Guaranteed or -Targeted, Pressure-Controlled Ventilation with Volume-Controlled Ventilation during Elective Surgery: A Systematic Review and Meta-Analysis. 10(6):1276. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5369936","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":373281085,"identity":"9a3971d9-d8e1-4370-b35b-0db8ff349f0d","order_by":0,"name":"Zhiwei Li","email":"","orcid":"","institution":"Nanjing University of Aeronautics and Astronautics","correspondingAuthor":false,"prefix":"","firstName":"Zhiwei","middleName":"","lastName":"Li","suffix":""},{"id":373281086,"identity":"2ad6012a-4663-43f3-863b-7139a74f3cb9","order_by":1,"name":"Yang Wu","email":"","orcid":"","institution":"Nanjing Forestry University","correspondingAuthor":false,"prefix":"","firstName":"Yang","middleName":"","lastName":"Wu","suffix":""},{"id":373281087,"identity":"1eeed324-0505-4bc4-88f5-8cf4efbadcdb","order_by":2,"name":"Yao Yu","email":"","orcid":"","institution":"Nanjing University of Aeronautics and Astronautics","correspondingAuthor":false,"prefix":"","firstName":"Yao","middleName":"","lastName":"Yu","suffix":""},{"id":373281088,"identity":"59fdf5fe-368e-489d-96e6-358d1a43724e","order_by":3,"name":"Kai Liu","email":"","orcid":"","institution":"Nanjing University of Aeronautics and Astronautics","correspondingAuthor":false,"prefix":"","firstName":"Kai","middleName":"","lastName":"Liu","suffix":""},{"id":373281089,"identity":"392a3d93-37e9-4833-8633-abd16378933b","order_by":4,"name":"Hang Tian","email":"","orcid":"","institution":"Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health","correspondingAuthor":false,"prefix":"","firstName":"Hang","middleName":"","lastName":"Tian","suffix":""},{"id":373281090,"identity":"2f2f7ace-0085-44d4-997c-c3ad241f4b2c","order_by":5,"name":"Jiafeng Yao","email":"","orcid":"","institution":"Nanjing University of Aeronautics and Astronautics","correspondingAuthor":false,"prefix":"","firstName":"Jiafeng","middleName":"","lastName":"Yao","suffix":""},{"id":373281091,"identity":"c9fc52b3-12e1-467f-b946-54a09f37537a","order_by":6,"name":"Qiuju Cheng","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/ElEQVRIie3PsWoCMRzH8RyBTP+SNSGWvkKOg2sLoq+ScHBdDtwcS+TALn2AiE/RxTki3HhdC3awi/MdlOJUWkXczDkWmu8QCPw+hCAUCv3F2PGMDHZOf/eBUnMxIXrTkLzHrbuI7IMktmTVl0b5BZ2X1cfn+E6XVqUC4BUkclHTFp5H3quHpFczPbEqF8DWcIsN5rPFeSJZkQo+PZBKgFzDvXEEX3nJ6OtI9FSAqkE61UUKwtsDyXBsnesm7C1PBapZMnneRpvWZMDtsvT+hdpsy3fjx+uXp1HjtBkMKS2XTesh+zAQhGJzukfm7PQ02f2Sm85ZKBQK/dt+AJR0UyrNN5DjAAAAAElFTkSuQmCC","orcid":"","institution":"Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health","correspondingAuthor":true,"prefix":"","firstName":"Qiuju","middleName":"","lastName":"Cheng","suffix":""}],"badges":[],"createdAt":"2024-11-01 02:23:28","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5369936/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5369936/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":70919545,"identity":"def95ec8-64ec-4ca5-8db2-7cb2e727cd7d","added_by":"auto","created_at":"2024-12-09 08:33:35","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":122385,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart of perioperative period and the study. EIT, electrical impedance tomography; VCV, volume controlled ventilation; PCV-VG, pressure controlled ventilation - volume guaranteed. AWAKE = before the induction of anesthesia; BEGIN = the beginning of anesthesia induction and VCV mode; MIDDLE-1 = the first phase of the surgery and VCV mode; MIDDLE-2 = the second phase of the surgery and PCV-VG mode; END = before postoperative wakefulness and PCV-VG mode; Pump, pneumoperitoneum operation. The tilt angle of the operating table α = 20°.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-5369936/v1/8b5754048c6f5e70d77e23ad.png"},{"id":70919546,"identity":"f3b31193-f77a-4068-93dc-5757d3a2af36","added_by":"auto","created_at":"2024-12-09 08:33:35","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":177540,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of EIT. (a) EIT Tidal Image. The EIT tidal image is divided equally from ventral to dorsal into four regions, denoted ROI 1-ROI 4. Using the ventral line as the reference axis, the y-axis is normalized to 0 for the ventral and 1 for the dorsal. (b) RVDI Distribution plot. Each pixel point in the RVDI plot represents the time required to reach 40% of the inspiratory maximum.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-5369936/v1/36ddd1480be77813c98adb9a.png"},{"id":70919548,"identity":"72bad752-9942-4d24-bb1c-1a5d009237d1","added_by":"auto","created_at":"2024-12-09 08:33:35","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":473822,"visible":true,"origin":"","legend":"\u003cp\u003eSamples of EIT tidal images and RVDI distribution plots. AWAKE = before the induction of anesthesia; BEGIN = the beginning of anesthesia induction and VCV mode; MIDDLE-1 = the first phase of the surgery and VCV mode; MIDDLE-2 = the second phase of the surgery and PCV-VG mode; END = before postoperative wakefulness and PCV-VG mode; CoV = center of ventilation. GI = global inhomogeneity. RVDI = regional ventilation delay index.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-5369936/v1/ff2062c4e53e64fe57e5b1d8.png"},{"id":70919547,"identity":"69d8a959-abf6-4669-85b5-736c7c27b2d8","added_by":"auto","created_at":"2024-12-09 08:33:35","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":138894,"visible":true,"origin":"","legend":"\u003cp\u003ePercentage of total tidal variation per region of interest. Each stacked bar shows the distribution of ventilation in the four regions of interest (ROI 1-ROI 4; also see Table 3). Ventilation regions are mainly distributed in ROI 2 and ROI 3. More balanced distribution of ventilation in the AWAKE phase. The percentage of ROI 2 ventilation increased in the BEGIN and MIDDLE-1 phases, indicating a ventral shift in ventilation. The percentage of ROI 3 ventilation increased in the MIDDLE-2 and END phases.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-5369936/v1/c2f2859d284fca3430d84c97.png"},{"id":70919550,"identity":"fc07474e-3240-4547-8504-6ba1199b39b9","added_by":"auto","created_at":"2024-12-09 08:33:35","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":137739,"visible":true,"origin":"","legend":"\u003cp\u003eBox plot (median with 25th and 75th percentiles) of EIT parameters in VCV and PCV-VG mechanical ventilation modes. (a) Center of Ventilation (CoV). PCV-VG mode had larger CoV than VCV mode in non-surgical period and surgical period. (b) Global Inhomogeneity (GI). PCV-VG arm had less GI than VCV arm in non-surgical period and surgical period. (c) Regional Ventilation Delay (RVDI). PCV-VG mode had less RVDI than VCV mode in non-surgical period and surgical period, which is same as GI.\u003c/p\u003e\n\u003cp\u003ens, no significant difference, * \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05, ** \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.01, *** \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.001\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-5369936/v1/6303d9dceb73a7b8b5a2d639.png"},{"id":72112065,"identity":"2832df17-d01f-400c-9cf4-6f1650d365e9","added_by":"auto","created_at":"2024-12-22 18:01:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1494238,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5369936/v1/5daf71f9-96cd-40a7-9afe-467225d42c71.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Evaluation of Mechanical Ventilation Modes in the Laparoscopic Perioperative Period with Electrical Impedance Tomography","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003ePerioperative lung protective ventilation reduces the risk of postoperative pulmonary complications and improves lung function and prognosis[\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Lung protective ventilation strategies aim to reduce potential lung injury from intraoperative mechanical ventilation by optimizing mechanical ventilation parameters[\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDuring the perioperative period of laparoscopic anesthesia, changes in position and pneumoperitoneum lead to the development of pulmonary atelectasis in the area of dependence, increasing the risk of local lung injury[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Timely adaptation of lung-protective ventilation strategies in the laparoscopic perioperative period is necessary. The main parameters used to monitor lung function intraoperatively are respiratory compliance and oxygenation index (PaO\u003csub\u003e2\u003c/sub\u003e/FiO\u003csub\u003e2\u003c/sub\u003e). However, evaluating the ventilatory status of the lungs using only these parameters is limited[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eElectrical impedance tomography (EIT) is a non-invasive, dynamic, visual medical monitoring technique that has been demonstrated to be valuable in guiding lung protective ventilation strategy[\u003cspan additionalcitationids=\"CR12 CR13\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. EIT provides information on impedance changes in the region of lung ventilation and allows the distribution of lung ventilation to be shown in the reconstructed images. In clinical anesthesia, EIT is mainly used to guide prone therapy, lung tidal volume monitoring, and pleural effusion detection[\u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. In particular, EIT has shown significant advantages in finding optimal positive end-expiratory pressure (PEEP) and reducing localized lung collapse[\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. However, uncertainty remains as to which mode of mechanical ventilation is more conducive to lung protective ventilation in the laparoscopic perioperative period. For the most part, clinical experience and subjectivity dominate.\u003c/p\u003e \u003cp\u003eThe two modes of mechanical ventilation commonly used in anesthesia machines are volume-controlled ventilation (VCV) mode and pressure controlled ventilation - volume guaranteed (PCV-VG) mode. In VCV mode, the anesthesia machine delivers gas to the patient's lungs according to a set tidal volume (TV) and a fixed flow rate. PCV-VG mode is designed to ensure that the patients receive both a stable ventilation pressure and a set tidal volume during ventilation. In addition, in PCV-VG mode, the anesthetist adjusts the pressure of each breath to achieve a preset tidal volume based on real-time measurements of lung compliance and resistance. Most researchers had evaluated two modes of mechanical ventilation in terms of respiratory mechanics, but the studies still have limitations[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn this study, we evaluated the impacts of VCV mode and PCV-VG mode on lung ventilation in the perioperative laparoscopic period from spatial and temporal perspectives according to EIT ventilation parameters. Our primary goal was to determine which mode of mechanical ventilation is more conducive to lung-protective ventilation in anesthesia clinics and to provide a guideline for the subsequent use of EIT in clinical practice.\u003c/p\u003e"},{"header":"2 Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Experimental ethics\u003c/h2\u003e \u003cp\u003e The trial was approved by the Ethics Committee of Guangzhou Women and Children Medical Centre (Guangzhou, China; ID: Sui Women's and Children's Corun Tong Zi [2022] No. 292B00). The clinical registration number is ChiCTR2400089365. All participants signed informed consent before enrollment. Twenty-four cardiorespiratory sound female patients requiring laparoscopic surgery were included in the study. Laparoscopic surgery was mainly performed for benign tumors of the ovaries, uterine fibroids, and secondary infertility. The patients entered the operating theatre and were connected to a monitoring system (monitoring heart rate, blood pressure, and oxygen saturation). To more sensitively monitor the impedance signals, the EIT electrode belt was placed slightly below the breast, roughly between the 4th and 5th ribs[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Anesthesia was induced with remimazolam (0.3 mg/kg), sufentanil (0.3 \u003cem\u003e\u0026micro;\u003c/em\u003eg/kg), cisatracurium (0.3 mg/kg) and propofol (2 mg/kg).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Experimental procedure\u003c/h2\u003e \u003cp\u003eThe trial procedure is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The laparoscopic perioperative period is divided into five phases. In the AWAKE phase, the patients are in the supine position, awake, and spontaneous breathing. Induction of anesthesia was followed by the BEGIN phase. The patients are in the supine position and intubated in VCV mode. Then enter the surgical period. In the MEDDLE 1 phase, the patients are in the recumbent position (head-down and feet-up position), pneumoperitoneum, and the VCV mode is maintained. In the MEDDLE 2 phase, the PCV-VG mode is used. In the END phase, at the end of the surgery, the patients return to the supine position and maintain the PCV-VG mode. PEEP in mechanical ventilation was set at 3\u0026ndash;4 cmH\u003csub\u003e2\u003c/sub\u003eO and initial tidal volume was set at 6\u0026ndash;8 ml/kg of weight. The respiratory rate was fixed at 12/min. Finally, the clinical data of 24 patients were statistically analyzed and targeted for screening.\u003c/p\u003e \u003cp\u003eEIT data were collected using the EIT-1000 (Suzhou Jiantong Medical Technology Co., Ltd., Jiangsu, China). The output signal of the EIT measuring system is an AC\u0026thinsp;=\u0026thinsp;1mA, 122kHz safety current. The EIT belt has 16 electrodes and the skin around the human chest is wiped with alcohol or saline before wearing to reduce the effects of contact impedance. Impedance tomography images were recorded at 20 fps with good and stable electrode contact.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Experimental program\u003c/h2\u003e \u003cp\u003eTo ensure the validity of the data, EIT voltage data were recorded after the waveform stabilized at each phase, and the recording duration was more than 10 min. For the MIDDLE-2 phase, EIT data were recorded 15 min after the respiratory signal had stabilized, and for the remaining four phases the recording started 5 min after the respiratory signal had stabilized. The 15-minute transition time in MIDDLE-2 is set to eliminate the potential effects of the VCV mode in MIDDLE-1 on the PCV-VG mode in MIDDLE-2. The image reconstruction algorithm of EIT is Gaussian-Newton regularization and the smoothness of the image is enhanced by convolutional filtering[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. The pixel size of each image is 128\u0026times;128.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Experimental parameters\u003c/h2\u003e \u003cp\u003eCenter of ventilation (CoV), global inhomogeneity (GI), and regional ventilation delay index (RVDI) are commonly used to quantify lung function in EIT[\u003cspan additionalcitationids=\"CR26\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. EIT tidal image is obtained by calculating impedance changes between the end-inspiratory and end-expiratory moments in one respiratory cycle in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Each pixel point in the image represents relative impedance changes in the chest. The parameters of EIT are obtained based on the EIT tidal images. The value of CoV higher than 50 indicates a larger proportion of dorsal ventilation. Conversely, the proportion of ventral ventilation is larger. This protocol is determined by the direction of the prescribed y-axis. GI reflects the homogeneity of pulmonary ventilation. Lower GI values indicate better consistency in the region of pulmonary ventilation. The value of RVDI reflects the delay in pulmonary ventilation. Lower GI values indicate less difference in ventilation times across regions of the lung.\u003c/p\u003e \u003cp\u003eFor the same patient, the EIT tidal images for the five phases were unified to the same color scale range and EIT ventilation parameters were calculated under the same contour. The averages of the EIT parameters for five consecutive respiratory cycles were taken for each phase.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Statistical Analysis\u003c/h2\u003e \u003cp\u003eThe experimental subjects of this study were female patients requiring laparoscopic surgery. The primary purpose was to compare the clinical differences of two mechanical ventilation modes, VCV and PCV-VG. For statistical convenience, the phase of mechanical ventilation in the laparoscopic perioperative period was divided into the non-surgical and surgical periods. The non-surgical period includes the BEGIN phase and the END phase. The surgical period includes the MIDDLE-1 phase and the MIDDLE-2 phase.\u003c/p\u003e \u003cp\u003eThis experiment was a statistical study of clinical parameters under different phases during the perioperative laparoscopic period, and it was a self-controlled study. Statistical parameters covered heart rate, mean arterial pressure, end-tidal carbon dioxide, respiratory compliance, peak pressure, plateau pressure, driving pressure (ΔP), and oxygenation index (PaO\u003csub\u003e2\u003c/sub\u003e/FiO\u003csub\u003e2\u003c/sub\u003e).\u003c/p\u003e \u003cp\u003eThe normal distribution of continuous variables was determined using the Shapiro-Wilk test. Results satisfying normality are expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD, and the same variable was analyzed under two phases using paired t tests. Continuous variables that do not satisfy normality are expressed as medians (interquartile ranges) using Wilcoxon tests. Statistically significant values were considered to have \u003cem\u003eP\u003c/em\u003e values less than 0.05. Statistical analyses were carried out using SPSS version 26.0.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results","content":"\u003cp\u003eA total of 24 patients underwent successful laparoscopic surgery with no adverse events or complications during the surgery. Four patients experienced prolonged poor electrode contact during the surgical period due to interference from surgical operation and environment noise. This part of the EIT data is considered invalid. So, we excluded the clinical data of these four patients and statistically analyzed the clinical data of the remaining 20 patients. Patient characteristics are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Two samples of EIT tidal images and RVDI distribution images in the perioperative period are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePatient Characteristics\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBasic Parameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLaparoscopic surgery\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;20)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge, median (IQR), year\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37 (30\u0026ndash;44)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeight, mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD, cm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e157.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWeight, mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD, kg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e55.3\u0026thinsp;\u0026plusmn;\u0026thinsp;12.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDuration of surgery,\u003c/p\u003e \u003cp\u003emean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD, min\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e142.7\u0026thinsp;\u0026plusmn;\u0026thinsp;63.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRespiratory rate,\u003c/p\u003e \u003cp\u003emedian (IQR), per min\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 (10\u0026ndash;14)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003eThe data are presented as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD or median (IQR).\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eComparing the BEGIN phase and END phase (non-surgical period), ΔP was statistically significantly different and the remaining parameters were not significantly different (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Comparing the MIDDLE-1 phase and the MIDDLE-2 phase (surgical period), plateau pressure and ΔP were statistically significantly different and the remaining parameters were not significantly different. Comparing the BEGIN phase and the MIDDLE-1 phase (both in VCV mode), the heart rate was not significantly different and the rest of the parameters were statistically significantly different. Comparing the MIDDLE-1 phase and MIDDLE-2 phase (both in PCV-VG mode), the heart rate, end-tidal carbon dioxide and oxygenation index were not significantly different. The rest of the parameters were statistically significantly different.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eVentilation Parameters\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eLaparoscopic surgery (N\u0026thinsp;=\u0026thinsp;20)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVCV mode\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePCV-VG mode\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e Value\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeart rate (per min)\u003c/p\u003e \u003cp\u003eNon-surgical period\u003c/p\u003e \u003cp\u003eSurgical period\u003c/p\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e Value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e66.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u003c/p\u003e \u003cp\u003e69.1\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8\u003c/p\u003e \u003cp\u003e0.354\u003cb\u003e*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u003c/p\u003e \u003cp\u003e70.1\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u003c/p\u003e \u003cp\u003e0.968\u003cb\u003e*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.359\u003cb\u003e*\u003c/b\u003e\u003c/p\u003e \u003cp\u003e0.274\u003cb\u003e*\u003c/b\u003e\u003c/p\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean arterial pressure (mmHg)\u003c/p\u003e \u003cp\u003eNon-surgical period\u003c/p\u003e \u003cp\u003eSurgical period\u003c/p\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e Value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e73.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.2\u003c/p\u003e \u003cp\u003e84.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.2\u003c/p\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e77.1\u0026thinsp;\u0026plusmn;\u0026thinsp;2.2\u003c/p\u003e \u003cp\u003e83.8\u0026thinsp;\u0026plusmn;\u0026thinsp;2.0\u003c/p\u003e \u003cp\u003e\u003cb\u003e0.004*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.236\u003cb\u003e*\u003c/b\u003e\u003c/p\u003e \u003cp\u003e0.882\u003cb\u003e*\u003c/b\u003e\u003c/p\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEnd-tidal carbon dioxide (mmHg)\u003c/p\u003e \u003cp\u003eNon-surgical period\u003c/p\u003e \u003cp\u003eSurgical period\u003c/p\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e Value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e39.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3\u003c/p\u003e \u003cp\u003e43.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1\u003c/p\u003e \u003cp\u003e\u003cb\u003e0.002*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e42.3\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7\u003c/p\u003e \u003cp\u003e43.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.4\u003c/p\u003e \u003cp\u003e\u003cb\u003e0.028*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.070*\u003c/p\u003e \u003cp\u003e0.064*\u003c/p\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCompliance (mL/cmH\u003csub\u003e2\u003c/sub\u003eO)\u003c/p\u003e \u003cp\u003eNon-surgical period\u003c/p\u003e \u003cp\u003eSurgical period\u003c/p\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e Value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e36.1\u0026thinsp;\u0026plusmn;\u0026thinsp;1.4\u003c/p\u003e \u003cp\u003e24.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8\u003c/p\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e38.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u003c/p\u003e \u003cp\u003e25.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9\u003c/p\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.115*\u003c/p\u003e \u003cp\u003e0.105*\u003c/p\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePeak pressure (cmH\u003csub\u003e2\u003c/sub\u003eO)\u003c/p\u003e \u003cp\u003eNon-surgical period\u003c/p\u003e \u003cp\u003eSurgical period\u003c/p\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e Value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13 (12\u0026ndash;14)\u003c/p\u003e \u003cp\u003e18 (16\u0026ndash;23)\u003c/p\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13 (11\u0026ndash;14)\u003c/p\u003e \u003cp\u003e17 (15\u0026ndash;21)\u003c/p\u003e \u003cp\u003e\u003cb\u003e0.002\u003c/b\u003e\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.431\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e0.059\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlateau pressure (cmH\u003csub\u003e2\u003c/sub\u003eO)\u003c/p\u003e \u003cp\u003eNon-surgical period\u003c/p\u003e \u003cp\u003eSurgical period\u003c/p\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e Value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7 (6\u0026ndash;8)\u003c/p\u003e \u003cp\u003e11 (9\u0026ndash;13)\u003c/p\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6 (5\u0026ndash;7)\u003c/p\u003e \u003cp\u003e10 (8\u0026ndash;11)\u003c/p\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.082\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e0.009\u003c/b\u003e\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDriving pressure (cmH\u003csub\u003e2\u003c/sub\u003eO)\u003c/p\u003e \u003cp\u003eNon-surgical period\u003c/p\u003e \u003cp\u003eSurgical period\u003c/p\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e Value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 (3\u0026ndash;5)\u003c/p\u003e \u003cp\u003e8 (6\u0026ndash;11)\u003c/p\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (2\u0026ndash;4)\u003c/p\u003e \u003cp\u003e7 (5\u0026ndash;8)\u003c/p\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.017\u003c/b\u003e\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e0.010\u003c/b\u003e\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePaO\u003csub\u003e2\u003c/sub\u003e/FiO\u003csub\u003e2\u003c/sub\u003e (mmHg)\u003c/p\u003e \u003cp\u003eNon-surgical period\u003c/p\u003e \u003cp\u003eSurgical period\u003c/p\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e Value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e496 (452\u0026ndash;668)\u003c/p\u003e \u003cp\u003e486 (433\u0026ndash;540)\u003c/p\u003e \u003cp\u003e\u003cb\u003e0.004\u003c/b\u003e\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e500 (376\u0026ndash;580)\u003c/p\u003e \u003cp\u003e468 (394\u0026ndash;538)\u003c/p\u003e \u003cp\u003e0.281\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.496\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e0.376\u003csup\u003e₭\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eMeasurements were taken at modes of mechanical ventilation (VCV and PCV-VG) during the surgery. The data are presented as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD or median (IQR). Each group of data corresponds to its row and column. Non-surgical period and VCV mode\u0026thinsp;=\u0026thinsp;BEGIN. Surgical period and VCV mode\u0026thinsp;=\u0026thinsp;MIDDLE-1. Surgical period and PCV-VG mode\u0026thinsp;=\u0026thinsp;MIDDLE-2. Non-surgical period and PCV-VG mode\u0026thinsp;=\u0026thinsp;END. \u003cem\u003eP\u003c/em\u003e values less than 0.05 are shown in bold. * is paired t test. ₭ is Wilcoxon test\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eEIT tidal images of 20 patients in 5 phases were counted and the mean ventilation percentage was calculated for each region of interest (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The stacked histogram of the percentage of the average ventilation is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. Intuitively, most of the ventilation regions are concentrated in the ROI2 and ROI3. The percentage of ventilation in the AWAKE phase is the baseline, with a 4% difference in the percentage of ventilation between ROI2 and ROI3. In the BEGIN phase, the ventilation percentage of ROI3 decreased by 8% compared to baseline, and the EIT image was shifted ventrally. In the MIDDLE-1 phase, the ventilation percentage of ROI3 reached 25.1%, a decrease of 21.2% compared to baseline. In the MIDDLE-2 phase, the ventilation percentage of ROI3 increased by 9.5% compared to the MIDDLE-1 phase, and the EIT image was shifted to the dorsal side. In the END phase, there was a 7.7% difference in the percentage of ventilation between ROI2 and ROI3, with more balanced ventral and dorsal ventilation.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eParameters of EIT\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAWAKE\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBEGIN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMIDDLE-1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMEDDLE-2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eEND\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eROI 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (3\u0026ndash;7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 (5\u0026ndash;9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9 (7\u0026ndash;13)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8 (5\u0026ndash;10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7 (5\u0026ndash;8)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eROI 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e43 (38\u0026ndash;48)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e54 (45\u0026ndash;59)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e64 (61\u0026ndash;70)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e55 (50\u0026ndash;60)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e50 (44\u0026ndash;52)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eROI 3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e46 (40\u0026ndash;52)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e36 (31\u0026ndash;47)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26 (18\u0026ndash;34)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e36 (26\u0026ndash;40)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e39 (36\u0026ndash;47)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eROI 4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 (5\u0026ndash;7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (1\u0026ndash;4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1 (0\u0026ndash;2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3 (1\u0026ndash;4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4 (3\u0026ndash;6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCoV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e51.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e47.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e42.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e46.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e48.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.80\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.87\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRVDI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.1\u0026thinsp;\u0026plusmn;\u0026thinsp;3.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e15.4\u0026thinsp;\u0026plusmn;\u0026thinsp;5.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e11.1\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003eROI 1\u0026ndash;ROI 4 are presented as median (IQR). CoV, GI and RVDI are expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD. Region of interest ROI 1 is ventral, whereas ROI 4 is dorsal. AWAKE\u0026thinsp;=\u0026thinsp;before the induction of anesthesia; BEGIN\u0026thinsp;=\u0026thinsp;the beginning of anesthesia induction and VCV mode; MIDDLE-1\u0026thinsp;=\u0026thinsp;the first phase of the surgery and VCV mode; MIDDLE-2\u0026thinsp;=\u0026thinsp;the second phase of the surgery and PCV-VG mode; END\u0026thinsp;=\u0026thinsp;before postoperative wakefulness and PCV-VG mode; Pump, pneumoperitoneum operation.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eBox plots of the EIT parameters in the VCV and PCV-VG mechanical ventilation modes are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. In the AWAKE phase, the mean value of CoV (51.4\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9) was higher than 50 (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). For both the non-surgical period and the surgical period, CoV in PCV-VG mode was statistically significantly higher than in VCV mode (48.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6 \u003cem\u003evs.\u003c/em\u003e 47.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7, P\u0026thinsp;\u0026lt;\u0026thinsp;0.01*; 46.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6 \u003cem\u003evs.\u003c/em\u003e 42.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.3, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001*). RVDI in PCV-VG mode was statistically significantly lower than in VCV mode (8.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1 \u003cem\u003evs.\u003c/em\u003e 10.1\u0026thinsp;\u0026plusmn;\u0026thinsp;3.9, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001*; 11.1\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8 \u003cem\u003evs.\u003c/em\u003e 15.4\u0026thinsp;\u0026plusmn;\u0026thinsp;5.1; P\u0026thinsp;\u0026lt;\u0026thinsp;0.001*). In the non-surgical period, GI was not significantly different between PCV-VG and VCV modes (0.80\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10 \u003cem\u003evs.\u003c/em\u003e 0.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08, P\u0026thinsp;=\u0026thinsp;0.067). However, in the surgical period, GI was statistically significantly lower in PCV-VG mode than in VCV mode (0.87\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15 \u003cem\u003evs.\u003c/em\u003e 1.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.28; P\u0026thinsp;\u0026lt;\u0026thinsp;0.01*).\u003c/p\u003e \u003cp\u003eIn VCV mode, CoV decreased statistically significantly by 4.5 from the BEGIN phase to the MIDDLE-1 phase (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001*). GI increased statistically significantly by 0.23 (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001*). RVDI increased statistically significantly by 5.3 (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001*). In PCV-VG mode, CoV increased statistically significantly by 2.7 from the MIDDLE-2 phase to the END phase (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001*). GI decreased statistically significantly by 0.1 (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001*). RVDI decreased statistically significantly by 2.6 (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001*).\u003c/p\u003e \u003cp\u003eIn the non-surgical period, CoV in PCV-VG mode increased by 1.7, GI decreased by 0.03, and RVDI decreased by 1.6 compared to VCV mode. In the surgical period, CoV in PCV-VG mode increased by 3.5, GI decreased by 0.16, and RVDI decreased by 4.3 compared to VCV mode.\u003c/p\u003e"},{"header":"4 Discussion","content":"\u003cp\u003eThis trial compared the impacts of VCV and PCV-VG modes on pulmonary ventilation in the laparoscopic perioperative period. Lung ventilation status was quantified using EIT image parameters. The main findings were: (1) After induction of anesthesia, the patients were shifted from the supine position to the recumbent position and pneumoperitoneum was performed. The ventilation region of the EIT image was shifted ventrally, with decreased ventilatory coherence and increased ventilatory delay. (2) After surgery, the patients returned from the recumbent position to the supine position, and the pneumoperitoneum was released. The ventilation region of the EIT image was shifted dorsally, with increased ventilatory coherence and decreased ventilatory delay. (3) Both in the non-surgical and surgical periods, pulmonary ventilation in PCV-VG mode was more balanced in the ventral and dorsal regions, with a better performance of ventilatory coherence and lower ventilatory delay compared to the VCV mode. (4) PCV-VG mode contributes more to lung protective ventilation compared with VCV mode and reduces the impacts of poor ventilation due to changes in position and pneumoperitoneum during laparoscopic surgery.\u003c/p\u003e \u003cp\u003eIn the AWAKE phase, the patients were supine position and spontaneous breathing. CoV\u0026thinsp;\u0026gt;\u0026thinsp;50 indicates a high percentage of dorsal ventilation. When the patients were mechanically ventilated after induction of anesthesia, CoV was mostly below 50, indicating that ventilation was concentrated in the ventral region. This clinical phenomenon is in line with previous research[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. When spontaneous breathing, gravity dependence causes ventilation to be offset dorsally[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. When mechanical ventilation is used, if a low PEEP is applied, it may lead to dorsal localized lung atelectasis and poor ventilation due to dorsal compression in the supine position[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFrom the BEGIN phase to the MIDDLE-1 phase, the region of lung ventilation is shifted ventrally. This result is similar to that in previous studies[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Decreased PaO\u003csub\u003e2\u003c/sub\u003e/FiO\u003csub\u003e2\u003c/sub\u003e implies that the alveolar ventilatory exchange function deteriorates. We further demonstrated that changes in position cause worse ventilation by the GI and RVDI parameters. Physiologically, the recumbent position (head-down and feet-up) and pneumoperitoneum cause the diaphragm to be forced up. The increased extent of compression on the dorsal side of the lungs results in dorsal alveolar collapse. Moreover, we found that ΔP increased and respiratory compliance decreased. It might be that the compression of the lungs causes airway resistance to increase, which leads to decreased pulmonary ventilation.\u003c/p\u003e \u003cp\u003eFrom the MIDDLE-1 phase to the MIDDLE-2 phase, the region of lung ventilation is shifted dorsally. Compared with VCV mode, PCV-VG mode improved the uniformity of pulmonary ventilation distribution and reduced ventilation delay. It is noticed that a decreasing trend in plateau pressure and ΔP. The explanation for this phenomenon is that PCV-VG mode reduces airway resistance and improves respiratory compliance[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. The alveolar collapse rate is reduced, ensuring effective ventilation of the lungs. Comparing the BEGIN and END phases also illustrates that PCV-VG mode is more conducive to pulmonary ventilation.\u003c/p\u003e \u003cp\u003eFrom the MIDDLE-2 phase to the END phase, the patients were released from the pneumoperitoneum and returned to supine position with improved ventilation. It was further verified that changes in position and pneumoperitoneum cause abnormal pulmonary ventilation. In addition, we found that the extent of ventilation loss induced by the transition from the non-surgical period to the surgical period in VCV mode was higher than the extent of ventilation improvement induced by the transition from the surgical period to the non-surgical period in PCV-VG mode. This indirectly reflects the low sensitivity of PCV-VG mode to external disturbances and the ability to adjust the ventilation strategy more flexibly.\u003c/p\u003e \u003cp\u003eWhen comparing the difference in mechanical ventilation modes between the non-surgical and surgical periods, we found that the improvement in pulmonary ventilation was more significant with PCV-VG mode than with VCV mode during the surgical period compared to the non-surgical period. In addition, GI was no significant difference between the two modes of mechanical ventilation during the non-surgical period. It is possible that pulmonary ventilation is less affected during the non-surgical period. There was little difference between the two modes of mechanical ventilation. When entering the surgical period, changes in position and pneumoperitoneum result in poor ventilation. At this point, PCV-VG mode is more helpful in alleviating poor ventilation. This also suggests that PCV-VG is a more alternative during laparoscopic surgery.\u003c/p\u003e \u003cp\u003eThe reason for using the before-after study in the same patient was considerations of individual pulmonary ventilation variability. We differ in that the ventilation contours and color bars of the EIT images of individuals under the five phases were harmonized, and all EIT parameters were calculated on a harmonized basis. We believe that EIT parameters calculated at the same level would be more valuable. However, this would also cause some statistical and order effects. Statistically, most of the clinical parameters were not statistically different between VCV and PCV-VG modes. Especially during the surgical period, although we analyzed the data after 15 min of changing PCV-VG mode, VCV mode of the previous phase could still potentially interfere with the ventilation parameters of PCV-VG mode.\u003c/p\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003eSignificant differences in EIT ventilation parameters between VCV and PCV-VG modes were observed during the laparoscopic perioperative period. Compared with VCV mode, PCV-VG mode improves ventilation inhomogeneity and ventilation delay due to intraoperative position and pneumoperitoneum. PCV-VG mode automatically adjusts pressure and reduces airway resistance during surgery. In summary, PCV-VG is a much better choice in the laparoscopic stage of surgery.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding Statement:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGuangzhou Municipal Science and Technology Project under Grant 2023A03J0862.\u003c/p\u003e\n\u003cp\u003eGuangDong Basic and Applied Basic Research Foundation under Grant 2022A1515220154.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of Interest:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Trial:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNumber: Sui Women\u0026apos;s and Children\u0026apos;s Corun Tong Zi [2022] No. 292B00.\u003c/p\u003e\n\u003cp\u003eEthics Committees: Ethics Committee of Guangzhou Women and Children Medical Centre.\u003c/p\u003e\n\u003cp\u003eDate: 2022/05/09.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Registration URL:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eChiCTR2400089365.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eZhiwei Li significantly contributed to the processing and analysis of EIT data associated with the work and drafting of the article and preparing Figure 3 - 5, Table 3.Yang Wu significantly contributed to EIT data analysis and preparing Table 1 - 2.Yao Yu significantly contributed to EIT data acquisition and preparing Figure 1 - 2.Kai Liu significantly contributed to the EIT system development and providing the article ideas.Hang Tian significantly contributed to the procedures for applying for ethical approval and the interpretation of data associated with the work.Jiafeng Yao significantly contributed to the interpretation of data associated with the work and reviewing the article.Qiuju Cheng contributed to the experimental design, the experimental execution, and providing the article ideas.All authors reviewed the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSevergnini P, Selmo G, Lanza C, Chiesa A, Frigerio A, Bacuzzi A, et al. 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Individualized Positive End-expiratory Pressure on Postoperative Atelectasis in Patients with Obesity: A Randomized Controlled Clinical Trial. Anesthesiology. 2023;139(3):262\u0026ndash;73.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang P, Zhao S, Gao Z, Hu J, Lu Y, Chen J. Use of volume controlled vs. pressure controlled volume guaranteed ventilation in elderly patients undergoing laparoscopic surgery with laryngeal mask airway. BMC ANESTHESIOL. 2021;21(1):69.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDeng C, Xu T, Wang X-k, Gu D-f. Pressure-controlled ventilation-volume guaranteed mode improves bronchial mucus transport velocity in patients during laparoscopic surgery for gynecological oncology: a randomized controlled study. BMC ANESTHESIOL. 2023;23(1):379.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKarsten J, Stueber T, Voigt N, Teschner E, Heinze H. 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BJA. 2020;125(3):373\u0026ndash;82.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVan Oosten JP, Francovich JE, Somhorst P, van der Zee P, Endeman H, Gommers DAMPJ, et al. Flow-controlled ventilation decreases mechanical power in postoperative ICU patients. INTENS CARE MED EXP. 2024;12(1):30.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRadke Oliver C, Schneider T, Heller Axel R, Koch T. Spontaneous Breathing during General Anesthesia Prevents the Ventral Redistribution of Ventilation as Detected by Electrical Impedance Tomography: A Randomized Trial. Anesthesiology. 2012;116(6):1227\u0026ndash;34.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZitzmann A, Pulletz S, Gonzales-Rios P, Frenkel P, Teschendorf P, Kremeier P et al. (2023) Regional ventilation in spontaneously breathing COVID-19 patients during postural maneuvers assessed by electrical impedance tomography. 67(2):185\u0026ndash;94.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBikker IG, Preis C, Egal M, Bakker J, Gommers D. Electrical impedance tomography measured at two thoracic levels can visualize the ventilation distribution changes at the bedside during a decremental positive end-expiratory lung pressure trial. CRIT CARE. 2011;15(4):R193.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUkere A, M\u0026auml;rz A, Wodack KH, Trepte CJ, Haese A, Waldmann AD, et al. Perioperative assessment of regional ventilation during changing body positions and ventilation conditions by electrical impedance tomography. BJA. 2016;117(2):228\u0026ndash;35.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchick V, Dusse F, Eckardt R, Kerkhoff S, Commotio S, Hinkelbein J et al. (2021) Comparison of Volume-Guaranteed or -Targeted, Pressure-Controlled Ventilation with Volume-Controlled Ventilation during Elective Surgery: A Systematic Review and Meta-Analysis. 10(6):1276.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-5369936/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5369936/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003ePurpose: \u003c/strong\u003eThe lung protective ventilation strategy has been advocated during the laparoscopic perioperative period. However, uncertainty remains as to which mode of mechanical ventilation is more appropriate in the laparoscopic perioperative period. We hypothesized the pressure controlled ventilation - volume guaranteed (PCV-VG) mode is a better option than the volume controlled ventilation (VCV) mode in the laparoscopic perioperative period.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethod: \u003c/strong\u003eThe trial was a self-controlled study. The laparoscopic perioperative period is divided into five phases: before induction of anesthesia (AWAKE), after induction of anesthesia (BEGIN), the first phase of the surgery (MIDDLE-1), the second phase of the surgery (MIDDLE-2), and before postoperative wakefulness (END). The BEGIN phase and MIDDLE-1 phase use the VCV mode, and the MIDDLE-2 phase and END phase use the PCV-VG mode. EIT data are recorded at each phase and the parameters of EIT were calculated to quantify the performance of pulmonary ventilation in space and time.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eDuring the non-surgical period, compared with VCV mode, PCV-VG mode had a significant increase in CoV (48.7 ± 2.6 \u003cem\u003evs.\u003c/em\u003e 47.0 ± 3.7, P \u0026lt; 0.01*), a significant decrease in RVDI (8.5 ± 3.1 \u003cem\u003evs.\u003c/em\u003e 10.1 ± 3.9) and no significant difference in GI (0.80 ± 0.10 \u003cem\u003evs.\u003c/em\u003e0.77 ± 0.08, P = 0.067). During the surgical period, compared with VCV mode, PCV-VG mode had a significant increase in CoV (46.0 ± 3.6 vs. 42.5 ± 3.3, P \u0026lt; 0.001*), a significant decrease in GI (0.87 ± 0.15 \u003cem\u003evs.\u003c/em\u003e 1.03 ± 0.28; P \u0026lt; 0.01*) and a significant decrease in RVDI (11.1 ± 3.8 \u003cem\u003evs.\u003c/em\u003e 15.4 ± 5.1; P \u0026lt; 0.001*)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion: \u003c/strong\u003eEIT ventilation parameters between VCV mode and PCV-VG mode have significant differences in the laparoscopic perioperative period. The PCV-VG mode could improve ventilation inhomogeneity and elevated ventilation delay due to changes in position and pneumoperitoneum during surgery. The PCV-VG mode might be better used to meet the changing demands for ventilation at different surgical stages. We believe that PCV-VG is a more alternative during laparoscopic surgery.\u003c/p\u003e","manuscriptTitle":"Evaluation of Mechanical Ventilation Modes in the Laparoscopic Perioperative Period with Electrical Impedance Tomography","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-09 08:33:31","doi":"10.21203/rs.3.rs-5369936/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"103c1f88-c28d-41a2-9127-8e91fcadc096","owner":[],"postedDate":"December 9th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-12-22T17:53:19+00:00","versionOfRecord":[],"versionCreatedAt":"2024-12-09 08:33:31","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5369936","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5369936","identity":"rs-5369936","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}