The efficacy of two oxygen therapy devices (nasal cannula vs. Simple mask) for preventing hypoxemia after general anesthesia: A randomized controlled non-inferiority trial of 500 patients

Objective: To compare the efficacy of two oxygen devices (nasal cannula and mask) and two flows for preventing hypoxemia in post anesthesia care unit (PACU). Material and Method: Five hundred (18-70 year old) patients were enrolled into a randomized, controlled non-inferiority trial at Siriraj Hospital, Mahidol University from May 2013 to December 2014. They received oxygen therapy after general anesthesia according to their groups by computer-generated randomization. Group I received oxygen nasal cannula 4 liters per minute and group II received oxygen mask 5 liters per minute. Both methods gave comparable FiO₂ (FiO₂ = 0.35). Inclusion criteria were elective surgery, American Society of Anesthesiologist (ASA) physical status 1-3. Exclusion criteria were unstable pulmonary disease, BMI >35 kg/m², baseline SpO₂ <94%, myopathy, alteration of consciousness, and nasal problems. The high-risk operations for post operative hypoxemia were excluded. The efficacy of two oxygen devices and flows were compared in term of preventing hypoxemia in PACU. Results: Five hundred patients were analyzed (249 patients in the cannula group and 251 patients in the mask group). They were comparable in demographics and operations. At PACU, none of 500 patients had SpO₂<94% (non-inferiority trial, 95% CI -0.0152, 0.0152). They were mildly sedated or fully awake and had no respiratory complications. Conclusion: In low risk patients undergoing low risk operations, both nasal cannula or simple mask with FiO₂ = 0.35 are equally effective for preventing hypoxemia in PACU.