Comparison of Delivered Volumes and Airway Pressures when Ventilating Through an Endotracheal Tube with Bag-Valve Versus Demand-Valve

Abstract

AbstractIntroduction:Use of an oxygen-powered demand-valve to ventilate through an endotracheal tube is considered inappropriate due to concern regarding excessive airway pressure.Hypothesis:It was hypothesized that ventilation through an endotracheal tube using a bag-valve (BV) device and the recently modified demand-valve (DV) would produce similar tidal volumes (Vt), minute ventilation (MV), and peak airway pressures (PAP).Methods:This is a prospective, randomized vitro experimental model. Subjects were blinded to volume and pressure gauges. Thirty-nine EMTs (mean age 27 years with mean experience five years) volunteered to ventilate a mechanical test lung through an endotracheal tube for 10 minutes. Each subject was randomized to BV or DV and to either normal (0.1 L/cm H2O) or poor (0.04 L/cm H2O) lung compliance. This DV delivers set flow of 40 L/min at maximum 50±5 cm H2O. Subjects were instructed to use their “usual” technique for an average size adult in respiratory arrest with normal heart rate and blood pressure. The Vt and PAP were recorded for each breat; the MV and maximum PAP (PAP-max) for each minute was noted. Data were analyzed using repeated measures ANOVA and Tuke multiple comparisons with alpha set at 0.05.Results:Overall average tidal volumes and minute ventilations were acceptable with both ventilalory devices at both normal and poor compliance for the first, fifth, and 10th minute of continuous ventilation. Average airway pressures and peak airway pressures during the first, fifth, and 10th minute of ventilation all were significantly higher with those of the bag-valve than with the use of the demandvalve at both normal and poor compliance.Conclusion:In this model, ventilation with bag-valve and demand-valve both provided more than adequate Vt and MV; values wer similar except for higher Vt with BV at normal compliance. However, DV yielded significantly lower PAP and PAPmax at both poor and normal compliance. These findings need corrobration in an in vivo model, but suggest that with proper training, demand-valve ventilation through an endotracheal tube may be preferable.