Determination of the anatomical angulation of the right upper-lobe bronchi and left main bronchi relative to the coronal plane: a retrospective CT analysis to guide the placement of double-lumen tubes

Determination of the anatomical angulation of the right upper-lobe bronchi and left main bronchi relative to the coronal plane: a retrospective CT analysis to guide the placement of double-lumen tubes | 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 Determination of the anatomical angulation of the right upper-lobe bronchi and left main bronchi relative to the coronal plane: a retrospective CT analysis to guide the placement of double-lumen tubes Li Zhao, Cheng Chi, Liqiang Zhao, Guangying Cui, Zhuo Liu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7460989/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 Background Double-Lumen Tubes (DLTs) remain the common method for One-Lung Ventilation (OLV) in clinical practice. Nevertheless, optimal size selection and accurate placement are still challenging. A precise understanding of the anatomical relationships among the trachea, bronchi, and surrounding structures is essential. This study aim to determine the true anatomical angulation of the right upper-lobe bronchi and the left main bronchi relative to the coronal plane. Methods In this retrospective study, 400 consecutive patients were enrolled: 200 aged 18–60 years and 200 aged > 60 years. High-resolution thoracic CT images of these patients was retrieved, and the following parameters were measured: cross-sectional area and perimeter at the origin of main bronchus, the angle between the right upper-lobe bronchial orifice and the coronal plane, and the angle between the left main bronchial orifice and the coronal plane. Results The right upper-lobe bronchi had a mean angulation of−5.35 ± 13.04° and the most often angled between − 10°~0° (36.2%), followed by -20°~ -10° (22.8%) and < -20°(9.8%), the left main bronchi was more acutely angled (−9.57 ± 12.60°) and the frequently formed angle of -10°~0° (38.2%), followed by -20°~-10° (25.3%) and < -20° (16%). Compared with the younger group (18–60 years, n = 200), patients older than 60 years group (n = 200) weighed slightly less (67.03 ± 12.13kg vs 64.63 ± 11.11kg, p = 0.04), whereas sex distribution, height and left main bronchial perimeter were similar ( p = 0.08). The older group exhibited significantly steeper posterior angulation of both the right upper-lobe bronchi (−7.70 ± 13.84° vs−3.00 ± 11.75°, p < 0.01) and the left main bronchi (-11.34 ± 12.20° vs -7.80 ± 12.77°, p < 0.01), a larger left main bronchial orifice area (1.44 ± 0.41cm 2 vs 1.36 ± 0.32 cm², p = 0.02), and a longer right main bronchial orifice perimeter (4.93 ± 0.81cm vs 4.75 ± 0.63 cm, p = 0.01), while the difference in right upper-lobe area (1.70 ± 0.51cm 2 vs 1.62 ± 0.43 cm²) did not reach significance ( p = 0.07). Conclusions Individualized rotation of right-sided double-lumen tube and left-sided double-lumen tube based on the angle of the right upper-lobe bronchi and the left main bronchi relative to the coronal plane on preoperative CT may improve the first attempt success rate of the intubation of double-lumen tubes. Double-lumen tubes Chest computed tomography image Anatomy Rotation Angle Figures Figure 1 Background One-lung ventilation (OLV) is indispensable for most thoracic surgical procedures. Double-lumen tubes (DLTs) are the widely used devices for OLV[1,2]. However, difficulties in selecting the correct size and achieving optimal positioning persist[3,4]. If the size of the DLTs is chosen incorrectly or the position of DLTs is placed improperly, the incidence of DLTs malposition intraoperative may increase[5,6]. So preoperative knowledges of tracheobronchial angulation and diameters are crucial. This study provides anesthesiologists with a method to understand the anatomy of the trachea and bronchus. Methods Study design and ethics This retrospective study was approved by the medical ethics committee of The First hospital of Qinhuangdao (No.2019A047) and all participants provided electronic informed consent for the use of their chest CT imaging data . We retrospectively reviewed the Picture Archiving and Communication System (PACS) database from June 2024 to June 2025. Inclusion and exclusion criteria Inclusion: adults aged >18 years with CT reported stating “no anatomical abnormalities of the trachea and bronchus”. Exclusion: right upper-lobe bronchi originating in the trachea, lobar consolidation, pleural effusion, atelectasis, intrathoracic mass, previous pneumonectomy or motion artifacts. Imaging parameters CT scans were acquired on PACS using 0.5-1 mm slice thickness and the anatomical definitions and the measurement steps were as follows: Step 1. Right upper lobe bronchi opening inclination angle: located the most clearly visible level of the right upper lobe bronchi, drew a straight line from the anterior edges of both scapulae (coronal reference line, CRL), then shifted the CRL upward. The angle between the CRL and the central axis of the right upper lobe bronchi was the “ right upper lobe bronchi opening inclination angle”. Values 0° indicated anteversion inclination (Figure 1A,1B). Step 2. Left main bronchi opening inclination angle: Drew a CRL, then shifted the CRL upward. The angle between the CRL and the line connecting the center point of the tracheal carina and the center point of the left main bronchi was the “ left main bronchi inclination angle”. Values0° indicated anteversion inclination (Figure 1C,1D). Step 3. On the planar view of the tracheal carina , the cross-sectional area and perimeter at the origins of the left and right main bronchus were measured (Figure 1E,1F). Statistical analysis Continuous variables were presented as mean ± SD. Comparisons were performed using independent t-tests (18-60years vs age > 60years). Pearson correlation assessed the relationship between age and inclination angle. All analyses were performed in SPSS 21.0 statistical software. Results Four-hundred patients met the inclusion criteria. The right upper-lobe bronchi had a mean angulation of -5.35±13.04° and the most often angled was -10°~0° (36.2 %), followed by -20°~-10° (22.8 %) and 10° (9.7 %); The left main bronchi was more acutely angled (-9.57±12.60°) and the most frequently formed an angle was -10°~0° (38.2 %), followed by -20°~-10° (25.3 %) and 10° (3.8 %); The cross-sectional area and the perimeter of right main bronchi opening were 1.66±0.47 cm² and 4.84±0.73 cm, The cross-sectional area and the perimeter of left main bronchi opening were 1.40±0.37 cm² and 4.38±0.78 cm (Table 1, Table 2). Age-stratified comparison: Compared with the younger group (18-60years, n=200), the > 60years group (n=200) weighed slightly less (67.03±12.13kg vs 64.63±11.11kg, p =0.04), whereas sex distribution and height were not difference ( p =0.08) (Table 3). The older group exhibited significantly steeper posterior angulation of both the right upper-lobe bronchi (-7.70° vs -3.00°, p <0.01) and the left main bronchi (-11.30° vs -7.80°, p <0.01), a larger left-main-bronchial orifice area (1.44cm² vs 1.36 cm², p =0.02), and a longer right upper-lobe bronchi perimeter (4.93cm vs 4.75 cm, p =0.01), while the difference in right upper-lobe bronchi opening area (1.70cm² vs 1.62 cm²) and and left-main-bronchus perimeter (4.40±0.97cm vs 4.35±0.52cm) did not reach significance ( p =0.07) (Table 4). Discussion The common complication afer intubating of DLTs is trauma to the airway and the main reasons are excessive diameter of DLTs or multiple intubations[7,8]. Especially the variable anatomy of the right upper-lobe bronchi makes positioning of right-sided DLT (R-DLT) particularly difficult [9~11]. However, R-DLT is mandatory in certain situations such as left pneumonectomy, left sleeve resection, or left lung transplantation. Therefore, in order to increase the success rate of DLTs intubation, anesthesiologists should be familiar with the anatomy of the patient's trachea and bronchus before intubation [12]. The results of this study showed that the right upper-lobe bronchi had a posteriorly angulation of -5.35±13.04° relative to the coronal plane and the most often angled between -10°~0° (36.2 %), followed by -20°~ -10° (22.8 %) and < -20° (9.8%); The left main bronchi was more acutely posteriorly angulation of (-9.57±12.60°) relative to the coronal plane and the most frequently formed an angle of -10°~0° (38.2 %), followed by -20°~-10° (25.3 %) and < -20° (16.0 %). Rajesh V. Patel, et al measured the inclination angle of the main bronchi relative to the median sagittal plane and found a mean angle of 108.4° between the left main bronchi and the trachea. They recommended rotating a L-DLT 110° counter-clockwise rather than the traditional 90°, directing the tip toward 11 o’clock[13], while, our study find the angle of left main bronchi relative to the coronal line was mostly posteriorly, but there was still a small number of patients whose angle was anteriorly . So, we suggested that the anesthesiologists need to understand this angle is forward or backward before intubation to determine the rotation angle during the intubation of L-DLT. In addition, we measured the angle between the center line of the left bronchus relative to the coronal line and our method making it easier for anesthesiologists to understand the existence of this angle. So individualized rotation of L-DLT based on the angle of the left main bronchi relative to the coronal line on preoperative chest CT may increase the success rate of L-DLT intubation for the first attempt in adult patients. We also measured the angle between the right upper lobe bronchi and the coronal line. The results of the right upper-lobe bronchi had a posteriorly angulation of -5.35±13.04° which providing a reference for the alignment of the R-DLT. Wei Yu et al. described repositioning a R-DLT into the left main bronchi when right upper-lobe occlusion occurred intra-operatively, which may obstruct the side port and compromise ventilation[14]. Their method is likely to clog the lateral orifice of the R-DLT, causing difficulties in fine drainage and increasing the risk during the operation for patients. So our methods to measured the opening angle of the right upper lobe bronchi orifice and the length of the carina to distal margin of right upper lobe bronchi orifice as the length of right main stem bronchi[15] before intubation may increase the success rate of alignment of R-DLT. In this study, we measured the cross-sectional area and perimeter at the origins of the left and right main bronchus on the planar view of the tracheal carina . The size selection of DLTs is primarily guided by matching the outer diameter of the DLTs at the bronchial cuffs to the longitudinal and transverse inner diameter of the left or right main bronchus measured via chest CT[16]. However, we find the main bronchus often exhibit an irregular, non-circular geometry. Consequently, sizing decisions based on the longitudinal and transverse inner diameter of the bronchus may lead to errors. So comparing the cross-sectional area and perimeter at the origin of the left or right main bronchus with the perimeter and cross-sectional area of the DLTs at the bronchial cuffs may improve the accuracy of DLTs size selection, which needs to be validated in future clinical studies. Our study also found that compared with the 18-60 years group, aged over 60 years group exhibited significantly steeper posterior angulation of both the right upper-lobe bronchi (-7.70° vs -3.00°, p < 0.01) and the left main bronchi (-11.30° vs -7.80°, p < 0.01). This finding is also consistent with early study that the angle widens with age [17~19], possibly due to kyphosis, reduced lung volumes or cardiac enlargement, and warrants further investigation. Limitations First, this is a retrospective, single-center study and racial or geographical variations were not explored; Second, determination of an individualized angle via the 2D CT; Third, CT scans were performed in supine quiet breathing, whereas general anesthesia and paralysis may alter mediastinal geometry; Fourth, the accuracy of the proposed methodology has not yet been corroborated by clinical evidence. Conclusion Individualized rotation of R-DLT and L-DLT based on the angle of the right upper-lobe bronchi and the left main bronchi on preoperative CT may improve the first attempt success rate during the intubation of DLTs. Declarations Funding This project source: Qinhuangdao S&T Plan Program (No. 201805A160) Authorship contribution statement Li Zhao: Conceptualization Investigation, Manuscript editing, Modify figures and tables; Cheng Chi: Formal analysis, Writing- original draft; Guangying Chui: Investigation, Writing-original draft; Liqiang Zhao: Collected all the patient initial data, writing-original draft; Zhuo Liu: Collected all the patient initial data and drafted the manuscript, revise the manuscript, pictures and critical revision. All authors read and approved the final manuscript. Acknowledgments None. Data availability The datasets generated and analyzed during the current study are available from the corresponding author on reasonable request. Ethic approval and consent to participate This retrospective study was approved by the medical ethics committee of The First hospital of Qinhuangdao (No.2019A047) and all participants provided electronic informed consent. Clinical trial number Not applicable Consent to Publish declaration Not applicable Competing interests The authors declare that they have no competing interests. References Shelley B, Macfie A, Kinsella J. Anesthesia for thoracic surgery: a survey of UK practice. J Cardiothorac Vasc Anesth. 2011;25:1014-7. Brodsky JB, Lemmens HJM. Left double-lumen tubes: clinical experience with 1170 patients. J Cardiothorac Vasc Anesth. 2003; 17:289-98. Inoue S, Nishimine N, Kitaguchi K, et al. Double lumen tube location predicts tube malposition and hypoxaemia during one lung ventilation. Br J Anaesth. 2004;92:195-201. Seo JH, Bae JY, Kim HJ, et al. Misplacement of left-sided double-lumen tubes into the right mainstem bronchus: incidence, risk factors and blind repositioning techniques. BMC Anesthesiol. 2015;15:157-63. Bussieres JS, Lacasse Y, Cote D, et al. Modified right-sided broncho-cath double lumen tube improves endobronchial positioning: a randomized study. Can J Anaesth. 2007;54:276-82. Benumof JL. Improving the design and function of double-lumen tubes. J Cardiothorac Anesth. 1988;2:729-33. Adolphs, N. et al. Dentoalveolar injury related to general anaesthesia: A 14 years review and a statement from the surgical point of view based on a retrospective analysis of the documentation of a university hospital. Dent Traumatol. 2011;27(1):10-4. Tikka, T. & Hilmi, O. J. Upper airway tract complications of endotracheal intubation. Br J Hosp Med (Lond). 2019; 80(8):441-7. Yoo JY, Kim DH, Choi H, et al. Disconnection technique with a bronchial blocker for improving lung deflation: a comparison with a double-lumen tube and bronchial blocker without disconnection. J Cardiothorac Vasc Anesth. 2014;28:904-7. Mourisse J, Liesveld J, Verhagen A, et al. Efficiency, efficacy, and safety of EZ-blocker compared with left-sided double-lumen tube for one-lung ventilation. Anesthesiology. 2013;118:550-61. Cohen E. Con: right-sided double-lumen endotracheal tubes should not be routinely used in thoracic surgery. J Cardiothorac Vasc Anesth. 2002; 16:249-52. Campos JH, Gomez MN. Right-sided double-lumen endotracheal tubes should be routinely used in thoracic surgery. J Cardiothorac Vasc Anesth. 2002;16:246-8. Rajesh V Patel, Brandon A Van Noord, Dakshesh Patel, et al. Determination of the True Inclination Angle of the Main Bronchi Relative to the Median Sagittal Plane for Placement of a Left-Sided Double-Lumen Tube. J Cardiothorac Vasc Anesth. 2017; 31(2):434-40. Wei Yu, Zijian Wang, Dapeng Gao, et al. A method for addressing right upper lobe obstruction with right-sided double-lumen endobronchial tubes during surgery: a randomized controlled trial. BMC Anesthesiol. 2018,18(1):130. Zhuo Liu, Meiqi Liu, Li Zhao, et al. Comparison of the accuracy of three methods measured the length of the right main stem bronchus by chest computed tomography as a guide to the use of right sided double-lumen tube. BMC Anesthesiol. 2022; 22(1):264. Guangying Cui, Li Zhao, Cheng Chi, et al. The feasibility and accuracy of the method for selecting the optimal size of double-lumen tube in thoracic surgery: a prospective, randomized controlled trial. Sci Rep. 2024;14(1):17539. Mi W, Zhang C, Wang H, et al. Measurement and analysis of the tracheobronchial tree in Chinese population using computed tomography. PLoS ONE. 2015;10:e0123177. Huiying Zhou, Yuda Fei, Yuelun Zhang, Xiang Quan, Jie Yi. Individualized rotation of left double lumen endobronchial tube to improve placement success rate: a randomized controlled trial. Respir Res. 2024, 25(1):184. Wani TM, Buchh B, AlGhamdi FS, et al. Tracheobronchial angles in children: three-dimensional computed tomography-based measurements. Paediatr Anaesth. 2018;28:463-467. Tables Table 1. Distribution of right upper lobe bronchial opening angles and left main bronchial opening angles. Opening angles Right upper lobe bronchial opening angles Left main bronchial opening angles > 20° (%) 2.0 1.0 10°~ 20° (%) 7.7 2.8 0 ~ 10° (%) 21.5 16.7 -10°~ 0° (%) 36.2 38.2 -20 ~ -10° (%) 22.8 25.3 < -20° (%) 9.8 16.0 Table 2. Right upper lobe bronchi inclination angle, left main bronchi inclination angle, right and left main bronchi opening area, right and left main bronchi opening perimeter Factor Average （n=400） Standard Deviation (n=400) Right upper lobe bronchi inclination angle (°) -5.35 13.04 Right main bronchi opening area (cm 2 ) 1.66 0.47 Right main bronchi opening perimeter (cm) 4.84 0.73 Left main bronchi inclination angle (°) -9.57 12.6 Left main bronchi opening area (cm 2 ) 1.40 0.37 Left main bronchi opening perimeter (cm) 4.38 0.78 Table 3. Demographic characteristics of patients in the two groups Characteristics of patients Aged > 60 years（n=200） Aged 18–60 years (n=200) p Gender (M/F, n) 81/119 64/136 0.08 Age (years) 66.20±3.39 52.10±8.13 0.00 Height (cm) 163.13±7.77 163.43±8.19 0.72 Weight (kg) 64.63±11.11 67.03±12.13 0.04 Table 4. Right upper lobe bronchi inclination angle, left main bronchi inclination angle, right and left main bronchus opening area, right and left main bronchus opening perimeter of patients in the two groups. Factor Aged > 60 years（n=200） Aged 18–60 years (n=200) p Right upper lobe bronchi inclination angle (°) -7.70±13.84 -2.99±11.75 0.00 Right main bronchi opening area (cm 2 ) 1.70±0.51 1.62±0.43 0.07 Right main bronchi opening perimeter (cm) 4.93±0.81 4.75±0.63 0.01 Left main bronchi inclination angle (°) -11.34±12.20 -7.80±12.77 0.00 Left main bronchi opening area (cm 2 ) 1.44±0.41 1.36±0.32 0.02 Left main bronchi opening perimeter (cm) 4.40±0.97 4.35±0.52 0.53 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. 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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-7460989","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":528778190,"identity":"552359a9-8a88-4e0e-b2d9-194d3a965139","order_by":0,"name":"Li Zhao","email":"","orcid":"","institution":"First Hospital of Qinhuangdao","correspondingAuthor":false,"prefix":"","firstName":"Li","middleName":"","lastName":"Zhao","suffix":""},{"id":528778191,"identity":"4bf82b8f-69fe-4862-8d45-be917171be17","order_by":1,"name":"Cheng Chi","email":"","orcid":"","institution":"First Hospital of 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1","display":"","copyAsset":false,"role":"figure","size":7825138,"visible":true,"origin":"","legend":"\u003cp\u003eA: Created a Coronal Reference Line (CRL, From the anterior edges of both scapulae); B: Shifted the CRL upward and the angle between CRL and the central axis of the right upper lobe bronchus was the “ right upper lobe opening inclination angle”; C: Drew a CRL from the anterior edges of both scapulae; D: Shifted the CRL upward and the angle intersected with the line connecting the center point of the tracheal carina and the center point of the left main bronchus was the “ left main bronchus inclination angle”; E: Measured the cross-sectional area of the starting parts of the left and right main bronchus; F: Measured the perimeter of the starting parts of the left and right main bronchus.\u003c/p\u003e","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7460989/v1/029da65aba0b5d4a9f356f80.jpg"},{"id":106414017,"identity":"9f44e92a-0dc0-4c6a-bbd1-42ade12104f3","added_by":"auto","created_at":"2026-04-08 10:06:41","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":8384448,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7460989/v1/6d1b86ef-2b10-4fb0-93af-233df85869b0.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Determination of the anatomical angulation of the right upper-lobe bronchi and left main bronchi relative to the coronal plane: a retrospective CT analysis to guide the placement of double-lumen tubes","fulltext":[{"header":"Background","content":"\u003cp\u003eOne-lung ventilation (OLV) is indispensable for most thoracic surgical procedures. Double-lumen tubes (DLTs) are the widely used devices for OLV[1,2]. However, difficulties in selecting the correct size and achieving optimal positioning persist[3,4]. If the size of the DLTs is chosen incorrectly or the position of DLTs is placed improperly, the incidence of DLTs malposition intraoperative may increase[5,6]. So preoperative knowledges of tracheobronchial angulation and diameters are crucial. This study provides anesthesiologists with a method to understand the anatomy of the trachea and bronchus.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eStudy design and ethics\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;\u003cstrong\u003eThis retrospective study was\u003c/strong\u003e \u003cstrong\u003eapproved\u003c/strong\u003e by\u0026nbsp;the medical ethics committee of\u0026nbsp;The First hospital of Qinhuangdao\u0026nbsp;(No.2019A047) and all participants provided electronic informed consent for the use of their chest CT imaging data\u003cstrong\u003e.\u003c/strong\u003e We retrospectively reviewed the\u0026nbsp;Picture Archiving and Communication System (PACS)\u0026nbsp;database from June 2024 to June 2025.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInclusion and exclusion criteria\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Inclusion: adults aged \u0026gt;18 years with CT reported stating “no anatomical abnormalities of the trachea and bronchus”.\u003cbr\u003e\u0026nbsp;Exclusion: right upper-lobe bronchi originating in the trachea, lobar consolidation, pleural effusion, atelectasis, intrathoracic mass, previous pneumonectomy or motion artifacts.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eImaging parameters\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;CT scans were acquired on PACS using 0.5-1 mm slice thickness and the anatomical definitions and the measurement steps were as follows:\u003cbr\u003e\u0026nbsp;Step 1. Right upper lobe bronchi opening inclination angle: located the most clearly visible level of the right upper lobe bronchi, drew a straight line from the anterior edges of both scapulae (coronal reference line, CRL), then shifted the CRL upward. The angle between the CRL and the central axis of the right upper lobe bronchi was the “ right upper lobe bronchi opening inclination angle”. Values\u0026lt;0° indicated posterior inclination, Values \u0026gt; 0° indicated anteversion inclination (Figure 1A,1B).\u003c/p\u003e\n\u003cp\u003eStep 2. Left main bronchi opening inclination angle: Drew a CRL, then shifted the CRL upward. The angle between the CRL and the line connecting the center point of the tracheal carina and the center point of the left main bronchi was the “ left main bronchi inclination angle”. Values\u0026lt;0° indicated posterior inclination, Values\u0026gt;0° indicated anteversion inclination (Figure 1C,1D).\u003c/p\u003e\n\u003cp\u003eStep 3. On the planar view of the tracheal\u0026nbsp;\u003cstrong\u003ecarina\u003c/strong\u003e, the cross-sectional area and perimeter at the origins of the left and right main bronchus were measured (Figure 1E,1F).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical analysis\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Continuous variables were presented as mean ± SD. Comparisons were performed using independent t-tests (18-60years\u0026nbsp;vs\u0026nbsp;age \u0026gt; 60years). Pearson correlation assessed the relationship between age and inclination angle. All analyses were performed in SPSS 21.0\u0026nbsp;statistical software.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eFour-hundred patients met the inclusion criteria. The right upper-lobe bronchi had a mean angulation of\u0026nbsp;-5.35±13.04°\u0026nbsp;and\u0026nbsp;the most often angled\u0026nbsp;was\u0026nbsp;-10°~0° (36.2 %), followed by\u0026nbsp;-20°~-10° (22.8 %)\u0026nbsp;and\u0026nbsp;\u0026lt; -20°\u0026nbsp;(9.8 %)\u0026nbsp;whereas 0°~10° (21.5 %),\u0026nbsp;\u0026gt; 10°\u0026nbsp;(9.7 %);\u0026nbsp;The left main bronchi was more acutely angled (-9.57±12.60°) and the\u0026nbsp;most frequently formed an angle\u0026nbsp;was\u0026nbsp;-10°~0° (38.2 %), followed by\u0026nbsp;-20°~-10° (25.3 %)\u0026nbsp;and \u0026lt; -20°\u0026nbsp;(16.0 %)\u0026nbsp;whereas 0°~10° (16.7 %) and\u0026nbsp;\u0026gt;10° (3.8\u0026nbsp;%); The\u0026nbsp;cross-sectional area and the perimeter of right main\u0026nbsp;bronchi\u0026nbsp;opening were\u0026nbsp;1.66±0.47\u0026nbsp;cm² and\u0026nbsp;4.84±0.73 cm,\u0026nbsp;The\u0026nbsp;cross-sectional area and the perimeter of left main\u0026nbsp;bronchi\u0026nbsp;opening\u0026nbsp;were\u0026nbsp;1.40±0.37\u0026nbsp;cm² and\u0026nbsp;4.38±0.78 cm\u0026nbsp;(Table 1, Table 2).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAge-stratified comparison: Compared with the younger group (18-60years, n=200), the \u0026gt; 60years\u0026nbsp;group (n=200) weighed slightly less (67.03±12.13kg vs\u0026nbsp;64.63±11.11kg, \u003cem\u003ep\u003c/em\u003e=0.04), whereas sex distribution and height were not difference (\u003cem\u003ep\u003c/em\u003e=0.08) (Table 3). The older group exhibited significantly steeper\u0026nbsp;posterior\u0026nbsp;angulation of both the right upper-lobe bronchi (-7.70° vs -3.00°, \u003cem\u003ep\u003c/em\u003e\u0026lt;0.01) and the left main bronchi (-11.30° vs -7.80°, \u003cem\u003ep\u003c/em\u003e\u0026lt;0.01), a larger\u0026nbsp;left-main-bronchial orifice\u0026nbsp;area (1.44cm² vs 1.36 cm², \u003cem\u003ep\u003c/em\u003e=0.02), and a longer right upper-lobe bronchi perimeter (4.93cm vs 4.75 cm, \u003cem\u003ep\u003c/em\u003e=0.01), while the difference in right upper-lobe bronchi opening area (1.70cm² vs 1.62 cm²) and and left-main-bronchus perimeter (4.40±0.97cm vs\u0026nbsp;4.35±0.52cm) did not reach significance (\u003cem\u003ep\u003c/em\u003e=0.07) (Table 4).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe common complication afer intubating of DLTs is trauma to the airway and the main reasons are excessive diameter of DLTs or multiple intubations[7,8]. Especially the variable anatomy of the right upper-lobe bronchi makes positioning of right-sided DLT (R-DLT) particularly difficult\u0026nbsp;[9~11].\u0026nbsp;However,\u0026nbsp;R-DLT is mandatory in certain situations such as left pneumonectomy, left sleeve resection, or left lung transplantation.\u0026nbsp;Therefore, in order to increase the success rate of DLTs intubation, anesthesiologists\u0026nbsp;should\u0026nbsp;be familiar with the anatomy of the patient's trachea and bronchus before intubation [12].\u003c/p\u003e\n\u003cp\u003eThe results of this study showed that the right upper-lobe bronchi had a posteriorly angulation of\u0026nbsp;-5.35±13.04°\u0026nbsp;relative to the coronal plane and\u0026nbsp;the most often angled between\u0026nbsp;-10°~0° (36.2 %), followed by\u0026nbsp;-20°~\u0026nbsp;-10° (22.8 %)\u0026nbsp;and\u0026nbsp;\u0026lt; -20°\u0026nbsp;(9.8%);\u0026nbsp;The left main bronchi was more acutely posteriorly angulation of (-9.57±12.60°) relative to the coronal plane and\u0026nbsp;the\u0026nbsp;most frequently formed an angle of\u0026nbsp;-10°~0° (38.2 %), followed by\u0026nbsp;-20°~-10° (25.3 %)\u0026nbsp;and \u0026lt; -20°\u0026nbsp;(16.0 %).\u0026nbsp;Rajesh V. Patel, et al\u0026nbsp;measured\u0026nbsp;the inclination angle of the main bronchi relative to the median sagittal plane\u0026nbsp;and found a mean angle of 108.4° between the left main bronchi and the trachea.\u0026nbsp;They recommended rotating a L-DLT 110° counter-clockwise rather than the traditional 90°, directing the tip toward 11 o’clock[13],\u0026nbsp;while, our study find the angle\u0026nbsp;of left main bronchi relative to\u0026nbsp;the\u0026nbsp;coronal line was mostly\u0026nbsp;posteriorly, but there was still a small number of patients whose angle was\u0026nbsp;\u003cstrong\u003eanteriorly\u003c/strong\u003e. So, we suggested that the anesthesiologists need to understand this angle is forward or backward before intubation to determine the rotation angle during the intubation of L-DLT. In addition, we measured the angle between the center line of the left bronchus\u0026nbsp;relative to\u0026nbsp;the coronal line and our method making it easier for anesthesiologists to understand the existence of this angle. So\u0026nbsp;individualized rotation of L-DLT based on the angle of the left main bronchi\u0026nbsp;relative to\u0026nbsp;the coronal line\u0026nbsp;on preoperative chest CT may increase the success rate of L-DLT intubation for the first attempt in adult patients.\u003c/p\u003e\n\u003cp\u003eWe also measured\u0026nbsp;the angle between the right upper lobe bronchi and the coronal line. The results of\u0026nbsp;the right upper-lobe bronchi had a posteriorly angulation of\u0026nbsp;-5.35±13.04°\u0026nbsp;which\u0026nbsp;providing a reference for the alignment of the R-DLT.\u0026nbsp;Wei Yu et al. described repositioning a R-DLT into the left main bronchi when right upper-lobe occlusion occurred intra-operatively, which may obstruct the side port and compromise ventilation[14]. Their method is likely to clog the lateral orifice of the\u0026nbsp;R-DLT, causing difficulties in fine drainage and increasing the risk during the operation for patients. So our methods to\u0026nbsp;measured\u0026nbsp;the opening angle of the right upper lobe\u0026nbsp;bronchi\u0026nbsp;orifice\u0026nbsp;and\u0026nbsp;the length of the carina to distal margin of right upper lobe\u0026nbsp;bronchi\u0026nbsp;orifice as the length of right main stem bronchi[15]\u0026nbsp;before intubation may increase the success rate of alignment of\u0026nbsp;R-DLT.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn this study, we measured the cross-sectional area and perimeter at the origins of the left and right main bronchus on the planar view of the tracheal\u0026nbsp;\u003cstrong\u003ecarina\u003c/strong\u003e.\u0026nbsp;The size\u0026nbsp;selection of DLTs\u0026nbsp;is primarily guided by matching the outer diameter of the\u0026nbsp;DLTs\u0026nbsp;at the bronchial cuffs\u0026nbsp;to the\u0026nbsp;longitudinal and transverse inner diameter\u0026nbsp;of the left or right main bronchus\u0026nbsp;measured\u0026nbsp;via chest CT[16]. However,\u0026nbsp;we find\u0026nbsp;the main bronchus often exhibit an irregular, non-circular geometry. Consequently, sizing decisions based on the\u0026nbsp;longitudinal and transverse inner diameter\u0026nbsp;of the bronchus may\u0026nbsp;lead to\u0026nbsp;errors.\u0026nbsp;So\u0026nbsp;comparing the cross-sectional area and\u0026nbsp;perimeter at the origin of the left or right main bronchus with the\u0026nbsp;perimeter and cross-sectional area of the\u0026nbsp;DLTs\u0026nbsp;at the bronchial cuffs\u0026nbsp;may\u0026nbsp;improve\u0026nbsp;the\u0026nbsp;accuracy\u0026nbsp;of DLTs size\u0026nbsp;selection, which\u0026nbsp;needs to be validated in future clinical studies.\u003c/p\u003e\n\u003cp\u003eOur study also found that compared with the 18-60\u0026nbsp;years\u0026nbsp;group, aged over 60\u0026nbsp;years\u0026nbsp;group exhibited significantly steeper posterior angulation of both the right upper-lobe bronchi (-7.70° vs -3.00°, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.01) and the left main bronchi (-11.30° vs -7.80°,\u003cem\u003e\u0026nbsp;p\u003c/em\u003e \u0026lt; 0.01). This finding is also consistent with early study that the angle widens with age [17~19], possibly due to kyphosis, reduced lung volumes or cardiac enlargement, and warrants further investigation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;First, this is a retrospective, single-center study and racial or geographical variations were not explored; Second, determination of an individualized angle via the 2D CT; Third, CT scans were performed in supine quiet breathing, whereas general anesthesia and paralysis may alter mediastinal geometry; Fourth, the accuracy of the proposed methodology has not yet been corroborated by clinical evidence.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIndividualized rotation of R-DLT and L-DLT based on the angle of the right upper-lobe bronchi and the left main bronchi on preoperative CT may improve the first attempt success rate during the intubation of DLTs.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis\u0026nbsp;project source: Qinhuangdao S\u0026amp;T Plan Program (No. 201805A160)\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLi Zhao: Conceptualization Investigation,\u0026nbsp;Manuscript editing, Modify figures and tables; Cheng Chi: Formal analysis, Writing- original draft; Guangying Chui: Investigation, Writing-original draft; Liqiang Zhao: Collected all the patient initial data, writing-original draft; Zhuo Liu: Collected all the patient initial data and drafted the manuscript, revise the manuscript, pictures and\u0026nbsp;critical revision.\u0026nbsp;All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003cbr\u003e\u003c/strong\u003eThe datasets generated and analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003ch3\u003eEthic approval and consent to participate\u003c/h3\u003e\n\u003cp\u003e\u003cstrong\u003eThis retrospective study was\u003c/strong\u003e \u003cstrong\u003eapproved\u003c/strong\u003e by\u0026nbsp;the medical ethics committee of The First hospital of Qinhuangdao\u0026nbsp;(No.2019A047) and all participants provided electronic informed consent.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Publish declaration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eShelley B, Macfie A, Kinsella J. Anesthesia for thoracic surgery: a survey of UK practice. J Cardiothorac Vasc Anesth. 2011;25:1014-7.\u003c/li\u003e\n\u003cli\u003eBrodsky JB, Lemmens HJM. Left double-lumen tubes: clinical experience with 1170 patients. J Cardiothorac Vasc Anesth. 2003; 17:289-98. \u003c/li\u003e\n\u003cli\u003eInoue S, Nishimine N, Kitaguchi K, et al. Double lumen tube location predicts tube malposition and hypoxaemia during one lung ventilation. Br J Anaesth. 2004;92:195-201.\u003c/li\u003e\n\u003cli\u003eSeo JH, Bae JY, Kim HJ, et al. Misplacement of left-sided double-lumen tubes into the right mainstem bronchus: incidence, risk factors and blind repositioning techniques. BMC Anesthesiol. 2015;15:157-63.\u003c/li\u003e\n\u003cli\u003eBussieres JS, Lacasse Y, Cote D, et al. Modified right-sided broncho-cath double lumen tube improves endobronchial positioning: a randomized study. Can J Anaesth. 2007;54:276-82. \u003c/li\u003e\n\u003cli\u003eBenumof JL. Improving the design and function of double-lumen tubes. J Cardiothorac Anesth. 1988;2:729-33.\u003c/li\u003e\n\u003cli\u003eAdolphs, N. et al. Dentoalveolar injury related to general anaesthesia: A 14 years review and a statement from the surgical point of view based on a retrospective analysis of the documentation of a university hospital. Dent Traumatol. 2011;27(1):10-4.\u003c/li\u003e\n\u003cli\u003eTikka, T. \u0026amp; Hilmi, O. J. Upper airway tract complications of endotracheal intubation. Br J Hosp Med (Lond). 2019; 80(8):441-7. \u003c/li\u003e\n\u003cli\u003eYoo JY, Kim DH, Choi H, et al. Disconnection technique with a bronchial blocker for improving lung deflation: a comparison with a double-lumen tube and bronchial blocker without disconnection. J Cardiothorac Vasc Anesth. 2014;28:904-7. \u003c/li\u003e\n\u003cli\u003eMourisse J, Liesveld J, Verhagen A, et al. Efficiency, efficacy, and safety of EZ-blocker compared with left-sided double-lumen tube for one-lung ventilation. Anesthesiology. 2013;118:550-61.\u003c/li\u003e\n\u003cli\u003eCohen E. Con: right-sided double-lumen endotracheal tubes should not be routinely used in thoracic surgery. J Cardiothorac Vasc Anesth. 2002; 16:249-52. \u003c/li\u003e\n\u003cli\u003eCampos JH, Gomez MN. Right-sided double-lumen endotracheal tubes should be routinely used in thoracic surgery. J Cardiothorac Vasc Anesth. 2002;16:246-8.\u003c/li\u003e\n\u003cli\u003eRajesh V Patel, Brandon A Van Noord, Dakshesh Patel, et al. Determination of the True Inclination Angle of the Main Bronchi Relative to the Median Sagittal Plane for Placement of a Left-Sided Double-Lumen Tube. J Cardiothorac Vasc Anesth. 2017; 31(2):434-40.\u003c/li\u003e\n\u003cli\u003eWei Yu, Zijian Wang, Dapeng Gao, et al. A method for addressing right upper lobe obstruction with right-sided double-lumen endobronchial tubes during surgery: a randomized controlled trial. BMC Anesthesiol. 2018,18(1):130.\u003c/li\u003e\n\u003cli\u003eZhuo Liu, Meiqi Liu, Li Zhao, et al. Comparison of the accuracy of three methods measured the length of the right main stem bronchus by chest computed tomography as a guide to the use of right sided double-lumen tube. BMC Anesthesiol. 2022; 22(1):264.\u003c/li\u003e\n\u003cli\u003eGuangying Cui, Li Zhao, Cheng Chi, et al. The feasibility and accuracy of the method for selecting the optimal size of double-lumen tube in thoracic surgery: a prospective, randomized controlled trial. Sci Rep. 2024;14(1):17539.\u003c/li\u003e\n\u003cli\u003eMi W, Zhang C, Wang H, et al. Measurement and analysis of the tracheobronchial tree in Chinese population using computed tomography. PLoS ONE. 2015;10:e0123177. \u003c/li\u003e\n\u003cli\u003eHuiying Zhou, Yuda Fei, Yuelun Zhang, Xiang Quan, Jie Yi. Individualized rotation of left double lumen endobronchial tube to improve placement success rate: a randomized controlled trial. Respir Res. 2024, 25(1):184.\u003c/li\u003e\n\u003cli\u003eWani TM, Buchh B, AlGhamdi FS, et al. Tracheobronchial angles in children: three-dimensional computed tomography-based measurements. Paediatr Anaesth. 2018;28:463-467.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1. Distribution of right upper lobe bronchial opening angles and left main bronchial opening angles.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"549\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003eOpening angles\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003eRight upper lobe bronchial opening angles\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003eLeft main bronchial opening angles\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003e\u0026gt; 20\u0026deg;\u0026nbsp;(%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003e2.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003e1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003e10\u0026deg;~ 20\u0026deg;\u0026nbsp;(%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003e7.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003e2.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003e0 ~ 10\u0026deg;\u0026nbsp;(%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003e21.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003e16.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003e-10\u0026deg;~ 0\u0026deg;\u0026nbsp;(%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003e36.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003e38.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003e-20 ~ -10\u0026deg;\u0026nbsp;(%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003e22.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003e25.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003e\u0026lt; -20\u0026deg;\u0026nbsp;(%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003e9.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003e16.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 2. Right upper lobe bronchi inclination angle, left main bronchi inclination angle, right and left main bronchi opening area, right and left main bronchi opening perimeter\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"560\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003eFactor\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003cp\u003e（n=400）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003eStandard Deviation\u0026nbsp;(n=400)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003eRight upper lobe bronchi\u0026nbsp;inclination angle (\u0026deg;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003e-5.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003e13.04\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003eRight main\u0026nbsp;bronchi\u0026nbsp;opening area (cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003e1.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003e0.47\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003eRight main\u0026nbsp;bronchi\u0026nbsp;opening perimeter (cm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003e4.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003e0.73\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003eLeft main bronchi inclination angle (\u0026deg;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003e-9.57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003e12.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003eLeft main\u0026nbsp;bronchi\u0026nbsp;opening area (cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003e1.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003e0.37\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003eLeft main\u0026nbsp;bronchi\u0026nbsp;opening perimeter (cm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003e4.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 175px;\"\u003e\n \u003cp\u003e0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eTable 3.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eDemographic characteristics of patients in the two groups \u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"565\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 185px;\"\u003e\n \u003cp\u003eCharacteristics of patients\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003eAged \u0026gt; 60 years（n=200）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003eAged 18\u0026ndash;60 years\u0026nbsp;(n=200)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 185px;\"\u003e\n \u003cp\u003eGender (M/F, n)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e81/119\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e64/136\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 185px;\"\u003e\n \u003cp\u003eAge (years)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e66.20\u0026plusmn;3.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e52.10\u0026plusmn;8.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e0.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 185px;\"\u003e\n \u003cp\u003eHeight (cm)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e163.13\u0026plusmn;7.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e163.43\u0026plusmn;8.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e0.72\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 185px;\"\u003e\n \u003cp\u003eWeight (kg)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e64.63\u0026plusmn;11.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e67.03\u0026plusmn;12.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 126px;\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eTable 4. Right upper lobe bronchi inclination angle, left main bronchi inclination angle, right and left main bronchus opening area, right and left main bronchus opening perimeter of patients in the two groups.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"563\" class=\"fr-table-selection-hover\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 189px;\"\u003e\n \u003cp\u003eFactor\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003eAged \u0026gt; 60 years（n=200）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003eAged 18\u0026ndash;60 years\u0026nbsp;(n=200)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eRight upper lobe bronchi\u0026nbsp;inclination angle (\u0026deg;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e-7.70\u0026plusmn;13.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e-2.99\u0026plusmn;11.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e0.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eRight main bronchi opening area (cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e1.70\u0026plusmn;0.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e1.62\u0026plusmn;0.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eRight main bronchi opening perimeter (cm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e4.93\u0026plusmn;0.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e4.75\u0026plusmn;0.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eLeft main bronchi inclination angle (\u0026deg;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e-11.34\u0026plusmn;12.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e-7.80\u0026plusmn;12.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e0.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eLeft main\u0026nbsp;bronchi\u0026nbsp;opening area (cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e1.44\u0026plusmn;0.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e1.36\u0026plusmn;0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eLeft main bronchi opening \u0026nbsp; \u0026nbsp; perimeter (cm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e4.40\u0026plusmn;0.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e4.35\u0026plusmn;0.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 125px;\"\u003e\n \u003cp\u003e0.53\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n"}],"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":"Double-lumen tubes, Chest computed tomography image, Anatomy, Rotation Angle","lastPublishedDoi":"10.21203/rs.3.rs-7460989/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7460989/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cb\u003eBackground\u003c/b\u003e\u003c/p\u003e\u003cp\u003eDouble-Lumen Tubes (DLTs) remain the common method for One-Lung Ventilation (OLV) in clinical practice. Nevertheless, optimal size selection and accurate placement are still challenging. A precise understanding of the anatomical relationships among the trachea, bronchi, and surrounding structures is essential. This study aim to determine the true anatomical angulation of the right upper-lobe bronchi and the left main bronchi relative to the coronal plane.\u003c/p\u003e\u003cp\u003e\u003cb\u003eMethods\u003c/b\u003e\u003c/p\u003e\u003cp\u003eIn this retrospective study, 400 consecutive patients were enrolled: 200 aged 18\u0026ndash;60 years and 200 aged\u0026thinsp;\u0026gt;\u0026thinsp;60 years. High-resolution thoracic CT images of these patients was retrieved, and the following parameters were measured: cross-sectional area and perimeter at the origin of main bronchus, the angle between the right upper-lobe bronchial orifice and the coronal plane, and the angle between the left main bronchial orifice and the coronal plane.\u003c/p\u003e\u003cp\u003e\u003cb\u003eResults\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe right upper-lobe bronchi had a mean angulation of\u0026minus;5.35\u0026thinsp;\u0026plusmn;\u0026thinsp;13.04\u0026deg; and the most often angled between \u0026minus;\u0026thinsp;10\u0026deg;~0\u0026deg; (36.2%), followed by -20\u0026deg;~ -10\u0026deg; (22.8%) and \u0026lt; -20\u0026deg;(9.8%), the left main bronchi was more acutely angled (\u0026minus;9.57\u0026thinsp;\u0026plusmn;\u0026thinsp;12.60\u0026deg;) and the frequently formed angle of -10\u0026deg;~0\u0026deg; (38.2%), followed by -20\u0026deg;~-10\u0026deg; (25.3%) and \u0026lt; -20\u0026deg; (16%). Compared with the younger group (18\u0026ndash;60 years, n\u0026thinsp;=\u0026thinsp;200), patients older than 60 years group (n\u0026thinsp;=\u0026thinsp;200) weighed slightly less (67.03\u0026thinsp;\u0026plusmn;\u0026thinsp;12.13kg vs 64.63\u0026thinsp;\u0026plusmn;\u0026thinsp;11.11kg, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.04), whereas sex distribution, height and left main bronchial perimeter were similar (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.08). The older group exhibited significantly steeper posterior angulation of both the right upper-lobe bronchi (\u0026minus;7.70\u0026thinsp;\u0026plusmn;\u0026thinsp;13.84\u0026deg; vs\u0026minus;3.00\u0026thinsp;\u0026plusmn;\u0026thinsp;11.75\u0026deg;, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01) and the left main bronchi (-11.34\u0026thinsp;\u0026plusmn;\u0026thinsp;12.20\u0026deg; vs -7.80\u0026thinsp;\u0026plusmn;\u0026thinsp;12.77\u0026deg;, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), a larger left main bronchial orifice area (1.44\u0026thinsp;\u0026plusmn;\u0026thinsp;0.41cm\u003csup\u003e2\u003c/sup\u003e vs 1.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.32 cm\u0026sup2;, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.02), and a longer right main bronchial orifice perimeter (4.93\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81cm vs 4.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.63 cm, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.01), while the difference in right upper-lobe area (1.70\u0026thinsp;\u0026plusmn;\u0026thinsp;0.51cm\u003csup\u003e2\u003c/sup\u003e vs 1.62\u0026thinsp;\u0026plusmn;\u0026thinsp;0.43 cm\u0026sup2;) did not reach significance (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.07).\u003c/p\u003e\u003cp\u003e\u003cb\u003eConclusions\u003c/b\u003e\u003c/p\u003e\u003cp\u003eIndividualized rotation of right-sided double-lumen tube and left-sided double-lumen tube based on the angle of the right upper-lobe bronchi and the left main bronchi relative to the coronal plane on preoperative CT may improve the first attempt success rate of the intubation of double-lumen tubes.\u003c/p\u003e","manuscriptTitle":"Determination of the anatomical angulation of the right upper-lobe bronchi and left main bronchi relative to the coronal plane: a retrospective CT analysis to guide the placement of double-lumen tubes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-17 02:10:23","doi":"10.21203/rs.3.rs-7460989/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":"2b0f89f6-77cb-430d-b3f9-c2e6f79547a1","owner":[],"postedDate":"October 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-08T09:53:51+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-17 02:10:23","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7460989","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7460989","identity":"rs-7460989","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}