Abstract
Objectives: This study examined the effects of various factors that might influence the fraction of oxygen in inspired air (FiO2) in a human and in a model system during nasal positive pressure treatments. Design and Methods: A healthy male volunteer and a mannequin head were each outfitted with a nasal continuous positive air pressure mask and pressure source (BiPAP S, Respironics, Murrysville, PA). Oxygen was added through either a side port in the mask or a port near the machine. Flow and FiO2were measured while varying inspiratory and expiratory pressures. Measurements were repeated with a leak added to the system and using different sites of oxygen administration. Results: In both the human and in the model system, increasing inspiratory pressure, thereby increasing flow, decreased FiO2inside the mask. In the model system, addition of a fixed leak caused an increase in flow and decrease in FiO2at any given level of inspiratory and expiratory pressure. Conclusion: In patients using nasal positive pressure therapy, variables of pressure, leak around the mask, and the site of oxygen delivery determine the inspired oxygen concentration when giving oxygen supplementation.
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Yoder, E.A., Klann, K. & Strohl, K.P. Inspired Oxygen Concentrations during Positive Pressure Therapy. Sleep Breath 8, 1–5 (2004). https://doi.org/10.1007/s11325-004-0001-y
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DOI: https://doi.org/10.1007/s11325-004-0001-y