The mechanisms of action of OptiflowTM Nasal High Flow (NHF) therapy differ from those of conventional therapies, as do the resulting physiological effects and clinical outcomes.

The Optiflow NHF therapy mechanisms of action are:

  • Respiratory support (through the reduction of dead space and delivery of a dynamic positive airway pressure)
  • Airway hydration/humidification
  • Patient comfort
  • Supplemental oxygen (if required)
Note: the above mechanisms of action for high flow apply to delivery through an Optiflow nasal cannula interface. The mechanisms of action differ when high flow is delivered through a tracheostomy or mask interface adapter.
Optiflow Mechanisms

Reduction of deadspace explained

Clearance of expired air in the upper airways, reduces rebreathing of gas high in CO2 and depleted of O2, resulting in an increase in alveolar ventilation.

Dynamic positive airway pressure explained

NHF creates breath and flow-dependent pressure, making inspiration
easier and promoting slow, deep breathing on expiration,
thereby increasing alveolar ventilation.

Airway hydration explained

Humidity enables the comfortable delivery of high flows. Optimized humidity emulates the natural balance of heat and moisture that occurs normally in healthy lungs and may help to maintain physiological stability in compromised airways.  

Patient comfort explained

Respiratory support delivered via a mask poses challenges for clinicians and patients. NHF therapy is delivered via a cannula. Better patient comfort may promote improved compliance.

Medical staff with Optiflow patient


Clinical evidence suggests that use of Optiflow NHF therapy provides improved comfort compared to conventional oxygen delivery devices1,2. A study in JAMA3 found significantly reduced skin breakdown and noted a lower nurse workload with Optiflow NHF therapy than with Bi-level non-invasive ventilation. Patients are able to eat, drink and sleep with the Optiflow interface and can talk with their caregivers and families.

  1. Roca et al. Respir Care. 2010.
  2. Lenglet et al. Respir Care. 2012.
  3. Stéphan et al. JAMA. 2015.

Supplemental oxygen (if prescribed) explained

If oxygen is prescribed the advantge of delivering it via NHF is that you can have some confidence in the accurate delivery of blended, humidified oxygen.


In the example illustrated, the maximum oxygen flow from the face mask (in the left pane) is limited to approximately 10 L/min which is not sufficient to meet the patient’s peak inspiratory demand of 50 L/min. To compensate for this deficit, 40 L/min of room air will be entrained for every breath, which will dilute the oxygen and deliver a variable (sometimes unknown) FiO2.

In our example (in the right pane), Optiflow NHF therapy is able to meet the patient’s entire inspiratory demand of 50 L/min, without the need for dilution of oxygen - this gives confidence in the delivery of a specified FiO2.


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