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

Background: The aim of this study was 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, O₂, CO₂, temperature, and humidity levels. Multiple runs of breathing were performed while manipulating levels of resistance (5-30 cm H₂O/L/s), gas mixtures (room air, 79% helium [He] and 21% O₂, and 70% He and 30% O₂), and leak levels (ultralow, low, and high). Results: We found significant reductions in work of breathing (up to 64%) while conserving gas with estimates of up to 10- to 54-fold reduction in medical gas wastage (P < .001). Specifically, at resistances of 5, 10, 20, and 30 cm H₂O/L/s, we demonstrated 64, 57, 36, and 7% reduction in work of breathing (P < .001). 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.