Evaluation of high flow nasal oxygenation as a technique for preoxygenation in full term pregnant women

Background and Aims: Obstetric airway guidelines recommend preoxygenation before the induction of general anesthesia to achieve an end tidal oxygen concentration of ≥90%. Recently, high flow nasal oxygenation (HFNO) has been evaluated as a technique for delivering a high concentration of oxygen using high flow rates to patients. We evaluated the use of HFNO as a technique for preoxygenation in full-term pregnant women. Methods: A cross-sectional observational study was conducted on 100 term pregnant women. They underwent preoxygenation using HFNO for 4 minutes (30 L/min for 30 secs followed by 50 L/min for 210 secs) and end tidal oxygen concentration (ETO2) was measured at the end of preoxygenation. The primary outcome was the percentage of women who achieved an expired oxygen concentration of ≥90% for the first expired breath. The secondary outcome was the acceptability and comfort of HFNO as compared to facemask preoxygenation using a 4-point Likert scale. Results: The percentage of women who achieved expired oxygen concentration of ≥90% after 4 minutes of HFNO preoxygenation was 32% [95% confidence interval (CI):22.7-41.3%] with the mean end tidal oxygen (SD) being 86.67 (3.4). 71% [mean (SD): 2.94 (0.92)] found nasal cannula and 56% [mean (SD): 2.67 (1.21)] found facemask comfortable and acceptable for preoxygenation (P value, 0.05). Conclusion: Although HFNO is a comfortable technique, when used for preoxygenation for 4 minutes, it did not achieve an acceptable level of preoxygenation (ETO2 ≥90% in 95% of individuals). Therefore, it is an inadequate technique for preoxygenation in term pregnant women.