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.