BVM - Do no harm
It’s been a busy day in the ED and you’ve had several cardiac arrests come in back to back. EMS calls in with another one just as they’re hitting the door. The patient is an adult, but you notice the BVM they’re using is much smaller than what you’re used to seeing. The medic says “The day has been so bad, we didn’t have time to get back to base to restock the rig. We only had a pediatric BVM.” Knowing that safe ventilation includes limiting tidal volumes and pressures, you wonder what the implications of using a pediatric BVM are.
Adult BVM usually have 1.9L in the bag while pediatric BVM are closer to 1L. Both of these are well in excess of the tidal volume we would want to administer in any patient smaller than 237kg (estimating a tidal volume of 8cc/kg ideal body weight). Recent attention towards safe ventilation with BVM has prompted researchers to look at using “pediatric” BVMs on adult patients with the hope that this approach would engineer out excessive tidal volumes.
A group from Capital Health in Hopewell, NJ studied this in a simulated CPR scenario. Healthcare professionals were asked to use both an adult and pediatric BVM setup to deliver ventilation during CPR. The average tidal volume delivered for an adult BVM was 807.7cc (11.5cc/kg IBW for a 70kg male) while the pediatric volume was 630.7cc (9cc/KG IBW for a 70kg male). Peak pressures during delivered breaths were also different - 17cmH2O for adult BVM and only 13.4cmH2O for pediatric. While different, both of these would be considered safe. There was no difference in respiratory rate so the minute ventilation was necessarily lower in the pediatric BVM setup.
What does this mean? Would using a smaller tidal volume during the brief period of BVM in a rescue or code scenario help patient outcomes or limit lung injury? We don’t know. But we do know excessive tidal volumes are associated with volutrauma (excessive alveolar distention) and should be avoided generally. Using a pediatric BVM may still yield excessive tidal volumes, but they are much closer to what is considered safe for an adult patient.
Reference: Dafilou B, Schwester D, Ruhl N, Marques-Baptista A. It’s In The Bag: Tidal Volumes in Adult and Pediatric Bag Valve Masks. Western Journal of Emergency Medicine: Integrating Emergency Care with Population Health. 2020;21(3). doi:10.5811/westjem.2020.3.45788