HIGH-FLOW NASAL OXYGEN DURING ANESTHESIA INDUCTION IN ADULTS WITH CLASS 3 OBESITY: EFFECTS ON SAFE APNEA TIME AND PERI-INTUBATION SAFETY

Abstract

Introduction: Patients with class 3 obesity have reduced functional residual capacity, increased oxygen consumption, and a shortened safe apnea time during induction of general anesthesia. These physiological features increase the risk of rapid peri-intubation desaturation. High-flow nasal oxygenation (HFNO) may improve oxygenation reserve by delivering warmed, humidified oxygen at high flow rates and by maintaining oxygen delivery during apnea. This study compared HFNO with standard face-mask preoxygenation in adults with class 3 obesity undergoing elective surgery under general anesthesia. Methods: In this prospective randomized comparative study, 80 adults with body mass index >40 kg/m2 scheduled for elective surgery with tracheal intubation were allocated to standard face-mask preoxygenation (10–12 L/min, FiO2 1.0; n=40) or HFNO (60 L/min, FiO2 1.0; n=40). Preoxygenation lasted 3 minutes in both groups. The primary oxygenation outcomes were the lowest peripheral oxygen saturation (SpO2 ) during induction and time to desaturation below 92 %. A secondary exploratory composite outcome included SpO2 <92 %, post-intubation end-tidal carbon dioxide (EtCO2 ) >40 mmHg, need for additional airway management measures, or inadequate mask ventilation. Results: Secondary composite events occurred in 60 patients (75 %) and were less frequent with HFNO than with facemask preoxygenation (60 % vs 90 %, p=0.004). HFNO was associated with a higher lowest SpO2 (96.0 % ± 3.3 vs 89.9 % ± 6.8; p<0.001) and a longer time to desaturation below 92% (189.4 ± 32.1 s vs 121.6 ± 27.8 s; p<0.001). Desaturation below 92 % occurred in 10.0 % of patients in the HFNO group and 50.0 % in the control group (p<0.001). Post-intubation EtCO2 >40 mmHg occurred more often after face-mask preoxygenation (85 % vs 55 %; p=0.007). Additional airway management measures were used in 55 % of the face-mask group and 10 % of the HFNO group (p<0.001), primarily because videolaryngoscopy was used more frequently in the face-mask group (50 % vs 10 %). In a post-hoc adjusted analysis including Mallampati class, Cormack–Lehane grade, and videolaryngoscopy, HFNO remained associated with lower odds of desaturation (adjusted OR 0.11; 95% CI 0.03–0.45; p=0.002). Discussion: HFNO improved peri-intubation oxygenation stability and prolonged time to desaturation during induction of general anesthesia in adults with class 3 obesity. The exploratory composite outcome should be interpreted cautiously because it included physiological and procedural components of different clinical weight. Larger multicenter studies are needed to confirm whether improved oxygenation metrics translate into fewer severe patient-centered complications.