High-flow nasal cannula oxygenation reduces postoperative hypoxemia in morbidly obese patients: a randomized controlled trial.

BACKGROUND: Postoperative pulmonary complications (PPCs) are common in high-risk surgical patients. Postoperative ventilatory management may improve their outcome. Supplemental oxygen through a high-flow nasal cannula (HFNC) has become an alternative to classical oxygenation techniques, although the results published for postoperative patients are contradictory. We examined the efficacy of HFNC in postoperative morbidly obese patients who were ventilated intraoperatively with an open-lung approach (OLA). METHODS: We performed an open, two-arm, randomized controlled trial in 64 patients undergoing bariatric surgery (N.=32 in each arm) from May to November 2017 at the Hospital Clínico of Valencia. Patients were randomly assigned to receive HFNC oxygen therapy at the time of extubation or to receive conventional oxygen therapy, both applied during the first three postoperative hours. Intraoperatively, a recruitment maneuver and individualized positive end-expiratory pressure was applied in all patients. The primary outcome was postoperative hypoxemia. RESULTS: All patients were included in the final analysis. There were no significant differences between the baseline characteristics. Postoperative hypoxemia was less frequent in the HFNC group compared to those who received standard care (28.6% vs. 80.0%, relative risk [RR]: 0.35; 95%CI: 0.150-0.849, P=0.009). Prevalence of atelectasis was lower in the HFNC group (31% vs. 77%, RR: 0.39; 95%CI: 0.166-0.925, P=0.013). No severe PPCs were reported in any patient. CONCLUSIONS: Early application of HFNC in the operating room before extubation and during the immediate postoperative period decreases postoperative hypoxemia in obese patients after bariatric surgery who were intraoperatively ventilated using an OLA approach.

The accuracy of postoperative, non-invasive Air-Test to diagnose atelectasis in healthy patients after surgery: a prospective, diagnostic pilot study.

OBJECTIVE: To assess the diagnostic accuracy of peripheral capillary oxygen saturation (SpO2) while breathing room air for 5 min (the 'Air-Test') in detecting postoperative atelectasis. DESIGN: Prospective cohort study. Diagnostic accuracy was assessed by measuring the agreement between the index test and the reference standard CT scan images. SETTING: Postanaesthetic care unit in a tertiary hospital in Spain. PARTICIPANTS: Three hundred and fifty patients from 12 January to 7 February 2015; 170 patients scheduled for surgery under general anaesthesia who were admitted into the postsurgical unit were included. INTERVENTION: The Air-Test was performed in conscious extubated patients after a 30 min stabilisation period during which they received supplemental oxygen therapy via a venturi mask. The Air-Test was defined as positive when SpO2 was ≤96% and negative when SpO2 was ≥97%. Arterial blood gases were measured in all patients at the end of the Air-Test. In the subsequent 25 min, the presence of atelectasis was evaluated by performing a CT scan in 59 randomly selected patients. MAIN OUTCOME MEASURES: The primary study outcome was assessment of the accuracy of the Air-Test for detecting postoperative atelectasis compared with the reference standard. The secondary outcome was the incidence of positive Air-Test results. RESULTS: The Air-Test diagnosed postoperative atelectasis with an area under the receiver operating characteristic curve of 0.90 (95% CI 0.82 to 0.98) with a sensitivity of 82.6% and a specificity of 87.8%. The presence of atelectasis was confirmed by CT scans in all patients (30/30) with positive and in 5 patients (17%) with negative Air-Test results. Based on the Air-Test, postoperative atelectasis was present in 36% of the patients (62 out of 170). CONCLUSION: The Air-Test may represent an accurate, simple, inexpensive and non-invasive method for diagnosing postoperative atelectasis. TRIAL REGISTRATION: NCT02650037.