I would like to highlight a recently published study. Despite the small numbers (30 healthy volunteers) it probably has important implications to our practice. It is titled: "Assessment of Common Preoxygenation Strategies Outside of the Operating Room Environment” and is authored by previous Monash and Alfred Health registrar, now London HEMS FACEM, Chris Groombridge.
From the conclusions - “...the effectiveness of BVM (bag-valve-mask) preoxygenation was comparable to the anesthetic circuit, and superior to preoxygenation with NRM (non-rebreather mask). The addition of nasal cannulae oxygen, PEEP, or both, did not improve the efficacy of the BVM device”.
This does not mean you shouldn’t continue using nasal cannulae oxygen for apneic oxygenation during induction, but you should probably preoxygenate using a BVM rather than NRM.
Objectives: Preoxygenation prior to intubation aims to increase the duration of safe apnea by causing denitrogenation of the functional residual capacity, replacing this volume with a reservoir of oxygen. In the operating room (OR) the criterion-standard for preoxygenation is an anesthetic circuit and well-fitting face mask, which provide a high fractional inspired oxygen concentration (FiO2). Outside of the OR, various strategies exist to provide preoxygenation. The objective was to evaluate the effectiveness of commonly used preoxygenation strategies outside of the OR environment.
Methods: This was a prospective randomized unblinded study of 30 healthy staff volunteers from a major trauma center emergency department (ED) in Sydney, Australia. The main outcome measure is fractional expired oxygen concentration (FeO2) measured after a 3 minute period of tidal volume breathing with seven different preoxygenation strategies.
Results: The mean FeO2 achieved with the anesthetic circuit was 81.0% (95% CI = 78.3% to 83.6%), bag-valve-mask (BVM) 80.1% (95% CI = 76.5% to 83.6%), BVM with nasal cannulae (NC) 74.8% (95% CI = 72.0% to 77.6%), BVM with positive end expiratory pressure valve (PEEP) 78.9% (95% CI = 75.4% to 82.3%), BVM + NC + PEEP 75.5% (95% CI = 72.2% to 78.9%), non-rebreather mask (NRM) 51.6% (95% CI = 48.8% to 54.4%), and NRM + NC 57.1% (95% CI = 52.9% to 61.2%). Preoxygenation efficacy with BVM strategies was significantly greater than NRM strategies (p < 0.01), and non-inferior to the anesthetic circuit.
Conclusions: In healthy volunteers, the effectiveness of BVM preoxygenation was comparable to the anesthetic circuit (criterion standard), and superior to preoxygenation with NRM. The addition of nasal cannulae oxygen, PEEP, or both, did not improve the efficacy of the BVM device.