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<or=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.
Cardiothoracic and Vascular Intensive Care Unit, Level 4, Building 32, Auckland City Hospital, Private Bag 92024, Auckland, New Zealand. rparke@adhb.govt.nz
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R
Parke
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S
McGuinness
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M
Eccleston
D000328:Adult; D000368:Aged; D000399:Air Pressure; D006348:Cardiac Surgical Procedures; D003422:Critical Care / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008397:Masks; D008875:Middle Aged; D009296:Nasal Cavity; D009305:Nasopharynx / Q000502:physiology; D011175:Positive-Pressure Respiration / Q000295:instrumentation / Q000379:methods*; D011182:Postoperative Care / Q000295:instrumentation / Q000379:methods; D011446:Prospective Studies