BJA Advance Access originally published online on October 20, 2009
British Journal of Anaesthesia 2009 103(6):886-890; doi:10.1093/bja/aep280
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Nasal high-flow therapy delivers low level positive airway pressure

1 Cardiothoracic and Vascular Intensive Care Unit, Level 4, Building 32, Auckland City Hospital, Private Bag 92024, Auckland 1010, New Zealand
2 Fisher and Paykel Healthcare, 1 Maurice Paykel Place, East Tamaki, Auckland, New Zealand
* Corresponding author. E-mail: rparke{at}adhb.govt.nz
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 OptiflowTM 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 H2O 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.
Keywords: airway pressure; nasal high-flow therapy; OptiflowTM; oxygen
Declaration of interest. Fisher and Paykel Healthcare Limited provides some funding to the Auckland District Health Board for the salary paid to the research nurse employed in the Cardiothoracic and Vascular Intensive Care Unit (CVICU), Auckland City Hospital. They also supplied the OptiflowTM circuits used in this study and paid for the statistical analysis. M.E. is now employed by Fisher and Paykel Healthcare Limited as a Research Scientist and is part of an employee share package. At the time of this study being undertaken, however, she was employed as a Research Nurse in the CVICU.