Journal
RESPIRATORY CARE
Volume 60, Issue 10, Pages 1397-1403Publisher
DAEDALUS ENTERPRISES INC
DOI: 10.4187/respcare.04028
Keywords
oxygen therapy; high-flow nasal therapy; humidification; airway pressure; lung volume
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Funding
- Fisher & Paykel Healthcare
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BACKGROUND: Previous research has demonstrated a positive linear correlation between flow delivered and airway pressure generated by high-flow nasal therapy. Current practice is to use flows over a range of 30-60 L/min; however, it is technically possible to apply higher flows. In this study, airway pressure measurements and electrical impedance tomography were used to assess the relationship between flows of up to 100 L/min and changes in lung physiology. METHODS: Fifteen healthy volunteers were enrolled into this study. A high-flow nasal system capable of delivering a flow of 100 L/min was purpose-built using 2 Optiflow systems. Airway pressure was measured via the nasopharynx, and cumulative changes in end-expiratory lung impedance were recorded using the PulmoVista 500 system at gas flows of 30-100 L/min in increments of 10 L/min. RESULTS: The mean age of study participants was 31 (range 22-44) y, the mean +/- SD height was 171.8 +/- 7.5 cm, the mean +/- SD weight was 69.7 +/- 10 kg, and 47% were males. Flows ranged from 30 to 100 L/min with resulting mean +/- SD airway pressures of 2.7 +/- 0.7 to 11.9 +/- 2.7 cm H2O. A cumulative and linear increase in end-expiratory lung impedance was observed with increasing flows, as well as a decrease in breathing frequency. CONCLUSIONS: Measured airway pressure and lung impedance increased linearly with increased gas flow. Observed airway pressures were in the range used clinically with face-mask noninvasive ventilation. Developments in delivery systems may result in this therapy being an acceptable alternative to face-mask noninvasive ventilation. (C) 2015 Daedalus Enterprises
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