Background: The ARDSnet trial showed an improvement in mortality with low-tidal volume ventilation to avoid baro- and volutrauma in the ventilated patient. These volumes are on the low end of predicted tidal volumes (~6 mL/kg), which falls far below the average tidal volume delivered by an adult bag valve mask (BVM) of 600-1000 mL per squeeze. With adult BVMs producing approximately twice the suggested lung protective volume, this group set out to determine whether appropriate lung ventilation could be achieved with a pediatric BVM. While this was evaluated in the prehospital setting previously, this study looks to evaluate adequacy of tidal volumes when delivered in an Emergency Department setting by a certified respiratory therapist.
Methods: Participants included certified respiratory therapists from a large academic hospital that had the opportunity to perform positive pressure ventilation with a BVM on an adult patient. Participants were asked to participate in a brief 15 minute test to ventilate an adult-sized patient simulator with both pediatric and adult-sized bag valve masks over 2 minute periods. Enrollment took place over three days. The range and average of tidal volumes ventilated on the simulated patients was aggregated and compared to protective lung volume measurements suggested the ARDSnet study referenced prior. The difference between adult and pediatric BVM results were compared separately.
Results: We enrolled 53 respiratory therapists with 9.2 mean years of experience. The mean tidal volumes for adult and pediatric BVMs were 800 and 517 mL respectively, for a difference of 283 mL (p 560 mL), 11.7% of breaths delivered were in range (420 to 560 mL) and 0.2% of breaths delivered were too low (<420 mL). By contrast, with the pediatric BVM, 84.5% of breaths were within range, 12.0% were too low, and 3.4% were too high. These differences were statistically significant, with a Chi-squared value of 2787 (p<0.0001).
Conclusion: The tidal volumes recorded with the pediatric BVM were more consistent with lung-protective ventilation volumes. The study confirms what the prior study showed: that ventilating an adult patient is possible with a smaller pediatric BVM while avoiding the barotrauma-inducing higher volumes more likely with an adult BVM.