High-flow versus standard nasal cannula in morbidly obese patients during colonoscopy: A prospective, randomized clinical trial

Study objective: Morbid obesity is associated with adverse airway events including desaturation during deep sedation. Prior works have suggested that proprietary high-flow nasal cannula devices generate positive pressure to all airway structures and may be superior to standard (low-flow) nasal cannula for prevention of desaturation. We hypothesized that, at a similar fraction of inspired oxygen (FiO ₂ ), use of a High-Flow Nasal Cannula (HFNC) at maximum flow rate would result in a lower incidence of intra-procedural desaturation episodes in morbidly obese patients compared to standard nasal cannula (SNC) during deep sedation with propofol. Design: This is a pragmatic, prospective, randomized clinical trial at one hospital (NCT03148262, UTSW#112016-058). Morbidly obese patients were randomized to HFNC during propofol sedation for colonoscopy. HFNC was performed using maximum flow rates of 60 liters per minute (LPM) and FiO ₂ of 0.36–0.40, whereas SNC was performed at 4LPM. The primary endpoint was incidence of arterial oxygen desaturation <90% measured by pulse oximetry. At midpoint enrollment the Data Monitoring Committee (DMC) performed a pre-planned O'Brien and Fleming futility test. Main results: Patients were randomized to HFNC (n = 28) or SNC (n = 31). Interim analysis of the primary endpoint showed that the desaturation rates in the HFNC group (39.3%) and the SNC group (45.2%) were not significantly different (p = 0.79). The DMC halted the trial at that point due to futility. Conclusion: At similar FiO ₂ , HFNC was not significantly different from SNC for prevention of arterial oxygen desaturation in morbidly obese patients undergoing propofol sedation for colonoscopy.