Raising the awareness for insufficient oxygen delivery from self-inflating resuscitation bags lacking expiratory valve during preoxygenation

We recently read an interesting study which demonstrated that self-inflating resuscitation bag (SIRB) lacking expiratory valve has unreliable performance in oxygen delivery during spontaneous breathing mimicked by mechanical lung simulator. It was postulated that the absence of an expiratory valve and the resulting air entrainment via the exhaust port accounts for the poor oxygen delivery performance. The current disposable SIRB in-use in our institutions (Med-Rescuer Disposable BVM Resuscitator 4000, BLS Systems Limited, ON, Canada) has a duckbill valve but no expiratory valve. Safety concerns regarding its oxygen delivery performance during spontaneous breathing were raised, as this SIRB was commonly used to preoxygenate critically ill patient with potentially transmissible respiratory infection (e.g. COVID-19) before tracheal intubation. We therefore performed an experiment on this SIRB using one of us as a healthy volunteer. Our small experiment demonstrated that air entrainment could occur via the exhaust port and affect oxygen delivery performance. Our experiment also demonstrated that attaching a positive end-expiratory pressure (PEEP) valve to the exhaust port improves the oxygen delivery performance. The findings of this experiment were sent to the relevant department of our institutions for safety consideration.