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.
Parke
R
R
Cardiothoracic and Vascular Intensive Care Unit, Level 4, Building 32, Auckland City Hospital, Private Bag 92024, Auckland, New Zealand. rparke@adhb.govt.nz
McGuinness
S
S
Eccleston
M
M
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