Nasal high-flow therapy delivers low level positive airway pressure

BACKGROUND: The aim of this prospective study was to determine whether a level of positive airway pressure was generated in participants receiving nasal high flow (NHF) delivered by the Optiflow™ system (Fisher and Paykel Healthcare Ltd, Auckland, New Zealand) in a cardiothoracic and vascular intensive care unit (ICU). METHODS: Nasopharyngeal airway pressure was measured in 15 postoperative cardiac surgery adult patients who received both NHF and standard facemask therapy at a flow rate of 35 litre min(−1). Measurements were repeated in the open mouth and closed mouth positions. Mean airway pressure was determined by averaging the pressures at the peak of inspiration of each breath within a 1 min period, allowing the entire pressure profile of each breath to be included within the calculation. RESULTS: Low level positive pressure was demonstrated with NHF at 35 litre min(−1) with mouth closed when compared with a facemask. NHF generated a mean nasopharyngeal airway pressure of mean (sd) 2.7 (1.04) cm H(2)O with the mouth closed. Airway pressure was significantly higher when breathing with mouth closed compared with mouth open (P≤0.0001). CONCLUSIONS: This study demonstrated that a low level of positive pressure was generated with NHF at 35 litre min(−1) of gas flow. This is consistent with results obtained in healthy volunteers. Australian Clinical Trials Registry www.actr.org.au ACTRN012606000139572.