Impact of early high flow nasal oxygen on diaphragmatic function and pulmonary complications after thoracic surgery: A randomized clinical trial

Background: Postoperative pulmonary complications (PPCs) are common after thoracic surgery, particularly in patients that develop postoperative diaphragmatic dysfunction. High-flow nasal cannula (HFNC) oxygen therapy decreases postoperative work of breathing and provides a positive end-expiratory pressure (PEEP) effect. As a result, it may decrease the occurrence of diaphragmatic dysfunction and PPCs after thoracic surgery. Methods: Single-centre, open-label, randomized controlled trial. Patients undergoing video-assisted thoracoscopic lobectomy were randomized to receive conventional oxygen therapy (COT) or high flow nasal cannula oxygen therapy. In both groups, inspiratory oxygen fraction was titrated to reach a peripheral oxygen saturation of >94 %. Diaphragmatic displacement (DD) and diaphragmatic thickening fraction (TF%) were measured 2 and 24 h after surgery. Diaphragmatic dysfunction was identified by DD <10 mm. PPCs occurring within 7 days after study enrollment were recorded. Results: We analyzed 116 patients in the study. Postoperative diaphragmatic dysfunction occurred in 17/58 patients (29 %) in the HFNC group compared to 21/58 (36 %) in the COT group (p = 0.55). The rate of PPCs was similar between the two groups: 32/58 (55 %) in the HFNC group and 37/58 (64 %) in the COT group (p =0.449). Patients who developed postoperative diaphragmatic dysfunction experienced fewer PPCs when treated with HFNC (20/37; 54 %) compared to COT (17/21; 81 %) (p = 0.037). A post hoc mixed-model analysis confirmed that HFNC reduced the risk of PPCs in patients with diaphragmatic dysfunction (OR 0.16, 95 % CI 0.02–0.83). Conclusions: Early HFNC support does not decrease the rate of postoperative diaphragmatic dysfunction rate or respiratory complications. In patients who develop postoperative diaphragmatic dysfunction, HFNC may play a role in mitigating the risk of PPCs. Clinical trial registration: NCT05532033