Low Pressure Heliox-based Rebreather System to Reduce Work of Breathing and Conserve Gas.

Abstract

Background: To test the ability of a low-pressure, low-flow, Heliox-based rebreathing system to reduce work of breathing and conserve gas while preserving CO2 concentration, temperature, and humidity at physiological levels in a bench study.Methods: We performed a bench study of a novel low-pressure, low-flow, noninvasive Heliox rebreathing system with CO2 scrubber that was connected to an artificial lung simulator with careful monitoring of flow, pressure, work of breathing, oxygen (O2), carbon-dioxide (CO2), temperature, and humidity levels. Multiple runs of breathing were performed while manipulating levels of resistance (5 - 30 cm H2O/L/sec), gas mixtures (room air, 79% Helium 21% O2, and 70% Helium and 30% O2), and leak levels (ultra-low, low, and high).Results: We found significant reductions in work of breathing (up to 64%) while conserving gas with estimates of up to 54-fold reduction in medical gas wastage (P<0.001). Specifically, at resistances of 5, 10, 20, and 30 cm H2O/L/sec we demonstrated 64%, 57%, 36%, and 7% reduction in work of breathing (P<0.0001). Gas wastage was reduced by 10- to 54-fold while the end-tidal CO2 concentration, humidity, and temperature were maintained by the device at physiological levels.Conclusions: In a bench-test, a low-pressure, low-flow, noninvasive Heliox rebreathing system with CO2 scrubber reduced work of breathing and conserved gas while preserving CO2 concentration, temperature, and humidity at physiological levels. Future studies in human subjects need to be performed to determine whether reduction of work of breathing and gas conservation can be achieved.