The Short-term Efficacy of High Flow Nasal Oxygen Therapy on Cardiovascular Surgical Patients: A Randomized Crossover Trial

Background: Oxygen therapy after extubation in the intensive care unit (ICU) is essential in order to maintain adequate oxygenation, especially in patients who have undertaken cardiovascular surgery. In such cases, a Venturi mask (VM) has been routinely used as an oxygen therapy in the ICU. Recently, however, the high flow nasal cannula (HFNC) has become available, and this device can deliver up to 60 L/min of humidified oxygen. The aim of this study is to evaluate the short-term efficacy between HFNC and VM in cardiovascular surgical patients. Methods: Forty patients who underwent cardiovascular surgery in 2015 were randomized to either protocol A (HFNC followed by VM) or protocol B (VM followed by HFNC). After 60-minutes of use with either device, arterial blood gas analysis was performed, and the PaO 2 /FiO 2 ratio (PFR) was calculated. Simultaneously, physiological data (respiratory rate, heart rate, mean arterial pressure, continuous cardiac index, and mixed venous oxygen saturation) were recorded. During this procedure, FiO 2 and gas flow were maintained at a fixed rate. These variables were compared by using the paired t-test, and a p value < 0.05 was considered significant. All data were expressed as mean (standard deviation). Results: Thirty-five patients (17 from protocol A and 18 from protocol B) were enrolled, and 5 patients were excluded from analysis in accordance with the exit criteria. PFR was significantly higher in the HFNC group than in the VM group [265.9 (81.4) vs. 238.7 (68.5), p=0.002]. Moreover, PaCO 2 was significantly lower in the HFNC group than in the VM group [33.8 (3.5) vs. 34.7 (2.9), p=0.033]. As for physiological data, the respiratory rate was significantly lower in the HFNC group than in the VM group [18 (4) vs. 21 (4), p=0.006], and no significant differences were seen in any of the other parameters. Conclusions: Compared to VM, HFNC ameliorated oxygenation function and decreased patients’ effort in breathing. HFNC also had little influence on their hemodynamic state when switched from VM. Therefore, HFNC can be used safely in cardiovascular surgical patients. Trial registration This trial was registered with the UMIN Clinical Trials Registry (ID UMIN000016572, February 18th, 2015, https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000019231).