The effects of flow on airway pressure during nasal high-flow oxygen therapy

Respir Care. 2011 Aug;56(8):1151-5. doi: 10.4187/respcare.01106. Epub 2011 Apr 15.


Background: Nasal high-flow oxygen therapy increases the mean nasopharyngeal airway pressure in adults, but the relationship between flow and pressure is not well defined.

Objective: To determine the relationship between flow and pressure with the Optiflow nasal high-flow oxygen therapy system.

Methods: We invited patients scheduled for elective cardiac surgery to participate. Measurements were performed with nasal high-flow oxygen at flows of 30, 40, and 50 L/min, with the patient's mouth both open and closed. Pressures were recorded over one minute of breathing, and average flows were calculated via simple averaging.

Results: With the mouth closed, the mean ± SD airway pressures at 30, 40, and 50 L/min were 1.93 ± 1.25 cm H(2)O, 2.58 ± 1.54 cm H(2)O, and 3.31 ± 1.05 cm H(2)O, respectively. There was a positive linear relationship between flow and pressure.

Conclusions: The mean nasopharyngeal pressure during nasal high-flow oxygen increases as flow increases. Australian Clinical Trials Registry

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Continuous Positive Airway Pressure / methods*
  • Follow-Up Studies
  • Humans
  • Middle Aged
  • Nasopharynx / physiopathology*
  • Oxygen Inhalation Therapy / methods*
  • Pressure
  • Prospective Studies
  • Respiration
  • Respiratory Insufficiency / physiopathology
  • Respiratory Insufficiency / therapy*
  • Treatment Outcome