An algorithmic approach to preoxygenation: Stepwise addition of pressure support and positive end-expiratory pressure when tidal volume breathing is inadequate. A randomised controlled trial

Background Preoxygenation is crucial for airway management safety. The standard method for preoxygenation is tidal volume breathing (TVB). This study aimed to determine whether an algorithmic approach which involves stepwise adding pressure support ventilation (PSV) and positive end-expiratory pressure (PEEP) when TVB is inadequate, would improve preoxygenation. Methods 200 patients planned for general anesthesia and having end-tidal oxygen (ETO ₂ ) < 90% after 3 min TVB were randomly divided into two: TVB was continued or 6 cmH ₂ O PSV was added. After 4 min, PSV patients having ETO ₂  < 90% were divided into two again: either PSV was continued or 4 cmH ₂ O PEEP was also added to PSV. The time to achieve ETO ₂  ≥ 90% and adverse effects were noted. Results After 4 min, patients with adequate preoxygenation was significantly lower with TVB (52%) compared with PSV (76%; P < 0.001). After 5 min, it was 97% and 100%, respectively. The mean durations of adequate preoxygenation with TVB, PSV and PSV-PEEP between 4–5 min were 274.90 ± 18.55, 268.94 ± 12.24 and 252.38 ± 7.46 s, respectively. The differences between TVB and PSV-PEEP (P < 0.001) and between PSV and PSV-PEEP (P = 0.001) were significant. Total time was significantly longer with TVB (237.17 ± 40.31 s) compared with PSV (222.63 ± 27.24 s; P = 0.003). Conclusions An algorithmic approach, stepwise adding PSV and PEEP in patients inadequately preoxygenated with standard TVB, ensures adequate preoxygenation in all patients and reduces the time required. Although this time difference was statistically significant, we considered that it was not clinically significant. No serious adverse effects were observed. Trial registration: NCT06736197