The Science Journal of the American Association for Respiratory Care

2007 OPEN FORUM Abstracts

HIGH FLOW NASAL OXYGEN THERAPY DELIVERS LOW LEVEL POSITIVE PRESSURE IN A STUDY OF 15 POST OPERATIVE CARDIAC PATIENTS

R. Parke1, M. Eccleston1, S. McGuinness1, C. Gerard2


Background: This investigation follows a study in healthy volunteers, where a low level of positive airway pressure was measured in subjects who were receiving high flow nasal oxygen therapy (1). A descriptive study was therefore carried out to determine whether similar results would be obtained in a patient population.

Methods: 15 cardio surgical patients were consented pre-operatively. During the post-operative period a 10F catheter was inserted into the hypopharyngeal space, via the nose, whilst participants were still sedated and ventilated. Measurements were then performed once the participant was awake and extubated. Placement of the hypopharyngeal catheter was confirmed at this time using end tidal CO2 monitoring. Measurements were performed with both a nasal interface (Fisher and Paykel Optiflow™ system) and standard face mask at gas flow = 35Lpm. Measurements were recorded with mouth open and mouth closed. The hypopharyngeal pressures were recorded over one minute of breathing. The mean airway pressure was determined by averaging the peak pressure from each breath over a one minute period. This allowed the entire pressure profile of each breath to be included within the mean airway pressure calculation.

Results: n=15. Average age = 63 years (41 – 79); average height = 175.4cms (156 – 186); average weight = 85.7kg (67 – 107). 86% (n=13) male.

At 35 Lpm with mouth closed, the Optiflow™ system with nasal interface delivered mean airway pressures of 2.70 cmH2O. Other results are described in table 1:

Conclusion: This study demonstrates that a low level of positive pressure is delivered using high flow nasal oxygen therapy, at 35Lpm of gas flow, in cardiac surgical patients. This is consistent with the results obtained in healthy volunteers. Further studies into high flow nasal oxygen therapy and its clinical applications are recommended.

Table 1

 Nasal Interface Mouth ClosedNasal Interface Mouth Open Face Mask Mouth Closed Face Mask Mouth Open
Mean Airway Pressure 2.70 cmH2O 1.23 cmH2O 0.2 cmH2O 0.11 cmH2O



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