Ventilation Strategies in the Obstructed Airway in a Bench Model Simulating a Nonintubated Respiratory Arrest Patient

Abstract

The Smart Bag MO(R) is an adult flow-limited bag-valve device designed to reduce the risk of stomach inflation in an unprotected airway. Its properties in severe airway obstruction are as yet unknown. In a bench model, we evaluated respiratory mechanics and delivered tidal volumes although ventilating at airway resistances of 4, 10, and 20 cm H(2)O . L(-1) . s(-1) once with a flow-limited bag-valve device and once with a standard bag-valve device to simulate a respiratory arrest patient with an unprotected airway. Inspiratory times were always longer with the flow-limited bag-valve device than with the standard bag-valve device. Lung tidal volume in the simulated unobstructed airway was 750 +/- 70 mL using the flow-limited bag-valve device versus 780 +/- 30 mL using the standard bag-valve device (n.s.); in the simulated medium obstructed airway it was 800 +/- 70 versus 850 +/- 20 mL (n.s.), and in the simulated severely obstructed airway it was 210 +/- 20 versus 170 +/- 10 mL (P < 0.01). Peak airway pressure in the simulated unobstructed airway was 15 +/- 2 cm H(2)O using the flow-limited bag-valve device versus 22 +/- 4 cm H(2)O using the standard bag-valve device (P < 0.01); in the simulated medium obstructed airway it was 22 +/- 1 versus 39 +/- 7 cm H(2)O (P < 0.01), and in the simulated severely obstructed airway it was 26 +/- 1 versus 61 +/- 3 cm H(2)O (P < 0.01). Stomach inflation in the simulated unobstructed airway was 0 mL/min using both bag-valve devices; in the simulated medium obstructed airway it was 0 mL/min for the flow-limited bag-valve device versus 200 +/- 20 mL/min for the standard bag-valve device (P < 0.01), and in the simulated severely obstructed airway it was 0 versus 1240 +/- 50 mL/min (P < 0.01). In a simulated severely obstructed unprotected airway, the use of a flow-limited bag-valve device resulted in longer inspiratory times, higher tidal volumes, lower inspiratory pressures, and no stomach inflation compared with a standard bag-valve device.