@article {Parke1397, author = {Rachael L Parke and Andreas Bloch and Shay P McGuinness}, title = {Effect of Very-High-Flow Nasal Therapy on Airway Pressure and End-Expiratory Lung Impedance in Healthy Volunteers}, volume = {60}, number = {10}, pages = {1397--1403}, year = {2015}, doi = {10.4187/respcare.04028}, publisher = {Respiratory Care}, abstract = {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{\textendash}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{\textendash}100 L/min in increments of 10 L/min.RESULTS: The mean age of study participants was 31 (range 22{\textendash}44) y, the mean {\textpm} SD height was 171.8 {\textpm} 7.5 cm, the mean {\textpm} SD weight was 69.7 {\textpm} 10 kg, and 47\% were males. Flows ranged from 30 to 100 L/min with resulting mean {\textpm} SD airway pressures of 2.7 {\textpm} 0.7 to 11.9 {\textpm} 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.}, issn = {0020-1324}, URL = {https://rc.rcjournal.com/content/60/10/1397}, eprint = {https://rc.rcjournal.com/content/60/10/1397.full.pdf}, journal = {Respiratory Care} }