Decreasing Peak Flow Rate with a New Bag-Valve-Mask Device: Effects on Respiratory Mechanics and Gas Distribution in a Bench Model of an Unprotected Airway

Horst G. Wagner-Berger, Volker Wenzel, Angelika Stallinger ,Wolfgang G. Voelckel, Klaus Rheinberger, Karl H. Stadlbauer,Sven Augenstein, Volker Dorges, Karl H. Lindner, Christoph Hormann
Department of Anaesthesiology and Critical Care Medicine, Leopold-Franzens-University, Anichstrasse 35, 6020 Innsbruck , Austria
Department of Anaesthesiology, University of Kiel , Kiel , Germany
Resuscitation 57 (2003) 193_/199

A bench model simulating a patient with an unintubated airway was used consisting of a face mask, manikin head, training lung (lung compliance, 100 ml/cm H2O, airway resistance 4 cm H2O/l/s, lower esophageal sphincter pressure 20 cm H2O and simulated stomach). Twenty nurses were randomized to each ventilate the manikin using a standard single person technique for 1 min (respiratory rate, 12/min) with either a standard adult self-inflating bag, or the SMART BAG†. The volunteers were blinded to the experimental design of the model until completion of the experimental protocol. The SMART BAG^® vs. standard self-inflating bag resulted in significantly lower peak inspiratory flow rates, peak inspiratory pressure, lung tidal volumes and stomach tidal volumes, longer inspiratory times, but significantly higher mask leakage; mask tidal volumes were comparable.

The mask leakage observed is not an uncommon factor in bag-valve-mask ventilation with leakage fractions of 25_ / 40% having been previously reported. The differences observed between the standard BVM and the SMART BAG^® are due more to the anatomical design of the mask and the non-anatomical shape of the manikin face than the function of the device. Future studies should remove the mask to manikin interface and should introduce a standardized mask leakage fraction. The use of a two-person technique may have removed the problem of mask leakage. In conclusion, using the SMART BAG^® during simulated ventilation of an unintubated patient in respiratory arrest significantly decreased inspiratory flowrate, peak inspiratory pressure, stomach tidal volume, and resulted in a significantly longer inspiratory time when compared to a standard self-inflating bag.