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 30–60 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.
Footnotes
- Correspondence: Rachael L Parke RN PhD, Cardiothoracic and Vascular Intensive Care Unit, Auckland City Hospital, Private Bag 92024, Auckland 1142, New Zealand. E-mail: rparke{at}adhb.govt.nz.
Research performed in the Cardiothoracic and Vascular Intensive Care Unit at Auckland City Hospital was supported in part by an unrestricted grant from Fisher & Paykel Healthcare. Fisher & Paykel Healthcare also supplied the consumables used in this study. This trial was registered prospectively at www.anzctr.org.au (ACTRN12613000047796). The authors have disclosed a relationship with Fisher & Paykel Healthcare.
Dr Parke presented a version of this report at the 26th Annual Congress of the European Society of Intensive Care Medicine, held October 5–9, 2013, in Paris, France.
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