Not all Bag Valve Masks are designed the same. One major difference is the presence of an expiratory valve. If your BVM does not have an expiratory valve it will entrain air when used for pre-oxygenation vastly impairing the amount of oxygen delivered to patients.
Many staff aren’t aware of this issue as the efficacy of preoxygenation is not assessed while it is being performed (in most environments outside the operating room). Within operating theatres end Tidal Oxygen Monitoring has been standard for some time and poor pre-oxygenation is readily identified.
While many clinicians point out that the addition of a PEEP valve overcomes the lack of expiratory valve, the PEEP valve makes it difficult for the patient to expire. They often in effect blow the mask away from their face impairing the seal leading to air entrainment (try it out on yourself – this issue quickly becomes obvious).
Expiratory valves should be made standard on all Bag Valve Masks. To aid this process we’ve created a list (see bottom of post) of Bag Valve Masks we recommend which have fixed expiratory valves, along with a list which don’t have fixed expiratory valves we suggest you replace.
This list is by no means exhaustive. We’d be most grateful if you could let us know of other BVMs not on this list and whether or not they have expiratory valves.
The images below (click here for video) demonstrate pre-oxygenation using the Mayo Healthcare BVM without expiratory valve. Note how the ETO2 does not rise above 60% due to the indrawing of air during spontaneous ventilation:
The images below (click here for video) demonstrate pre-oxygenation using the Laerdel BVM with fixed expiratory valve. Note how the ETO2 reaches >90% within 46 seconds.
Is it time for all in hospital locations of airway management to be able to access ETO2 monitoring – perhaps it’s impossible to provide adequate pre-oxygenation without the feedback provided by oxygen analysers (see here).
Bag Valve Masks With Expiratory Valves
– Laerdel Silicone Resuscitator
– Air Viva
– MayoHealthcare 2204 removable expiratory cap may be left off
Bag Valve Masks Without Expiratory Valves
– AirFlow Manual Resuscitator (has pressure gauge which may help reduce excessive inflation pressures)
– Portex 1st Response
Another way to assess if your BVM has an expiratory valve involves sacrificing a BVM and is demonstrated in the video (click on image) below. It requires cutting the bag part off the BVM with a scalpel then making an airtight occlusion over this opening with your hand. If one can suck in through the inspiratory port then the BVM lacks an inspiratory valve and will allow air entroainment during spontaneous breathing and preoxygenation: