Determining the effective pre‐oxygenation interval in obstetric patients using high‐flow nasal oxygen and standard flow rate facemask: a biased‐coin up–down sequential allocation trial. (11th February 2020)

• Record Type: Journal Article
• Authors: Au, K.; Shippam, W.; Taylor, J.; Albert, A.; Chau, A.
• Is Part Of: Anaesthesia. Volume 75:Number 5(2020)
• Page Start: 609
• Page End: 616
• Publication Date: 2020-02-11
• Subjects: difficult airway: caesarean section -- high‐flow nasal oxygen -- hypoxia general anaesthesia: pregnancy -- management of difficult airway -- pre‐oxygenation; Anesthesia -- Periodicals; 617.96
• DOI: 10.1111/anae.14995
• Languages: English
• ISSNs: 0003-2409

Abstract

Summary: Using biased‐coin sequential allocation, we sought to determine the effective time interval in 90% of healthy parturients to achieve a target endpoint end‐tidal oxygen of ≥ 90% using standard flow rate facemask and high‐flow nasal oxygen. Eighty healthy parturients were randomly assigned to standard facemask (n = 40) or high‐flow nasal oxygen (n = 40) groups; half of the parturients in the high‐flow nasal oxygen group also used a simple no‐flow facemask to minimise air entrainment. The effective time interval for 90% of parturients to achieve the target endpoint for standard facemask was 3.6 min (95%CI 3.3–6.7 min), but could not be estimated for the high‐flow nasal oxygen groups with or without an additional simple facemask, as eight minutes was insufficient to achieve the target endpoint for 55% and 92% of parturients, respectively. Furthermore, after three minutes, the target endpoint was reached by 71% in the standard facemask group vs. 0% in the high‐flow nasal oxygen groups. After four minutes, the target endpoint was reached by 100% in the standard facemask, 80% in the high‐flow nasal oxygen with simple facemask and 67% in the high‐flow nasal oxygen groups. Beyond four minutes, there was no improvement in pre‐oxygenation success using high‐flow nasal oxygen. In conclusion, under the conditions of our study, the effective time interval for 90% of parturients to achieve an end‐tidal oxygen ≥ 90% for standard flow rate facemask was estimated to be 3.6 min, but could not be estimated for high‐flow nasal oxygen groups even after eight minutes.