Background: Preoxygenation using a bag valve mask (BVM) with a filter is recommended to reduce the risk of viral transmission. Preoxygenation in hypoxaemic patients may require a positive end-expiratory pressure (PEEP) valve. Applying a filter to a BVM with or without a PEEP valve can increase resistance and work of breathing.

Objective: To evaluate the efficacy of proximal oxygen added to BVM with mechanical filter in healthy volunteers.

Materials and Methods: The present study was a crossover trial that randomized 48 volunteers to receive four preoxygenation techniques: BVM with a filter as group F, BVM with a filter and proximal oxygen as group FO, BVM with a filter and PEEP valve as group FP, and BVM with a filter, PEEP valve, and proximal oxygen as group FPO. Fraction of expired oxygen (FEO_₂) and continuous positive airway pressure (CPAP) were measured. Comfort was assessed using a numerical rating scale (NRS). The primary outcome was FEO₂ at five minutes.

Results: Data from 46 volunteers were analyzed. Adding oxygen proximal to the filter in the FO group increased FEO_₂ at five minutes by 7.07% (95% CI 4.87 to 9.26) and decreased the time to reach FEO_₂ 90% by 301.74 seconds (95% CI 282.82 to 320.66) compared with the times in group F. Similarly, supplemental proximal oxygen including a PEEP valve increased FEO₂ at five minutes by 6.07% (95% CI 3.87 to 8.26) and decreased the time to reach FEO₂ 90% by 242.13 seconds (95% CI 223.21 to 261.05). CPAP was 2.27, 3.61, 11.65, and 13.14 mmHg in group
F, FO, FP, and FPO, respectively. The NRS score was 6.51 and 6.07 in groups
F and FO, and 3.15 and 3.70 in groups FP and FPO, respectively.

Conclusion: Adding proximal oxygen to a BVM with a filter improved the efficacy of preoxygenation.