Respiration and the Airway
Nasal high-flow therapy delivers low level positive airway pressure

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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 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
Optiflow™
oxygen

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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 Optiflow™ 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.