Search Optiflow FAQs

How does nasal high flow (NHF) compare to conventional oxygen therapy (COT)?

COT via a low-flow cannula and most styles of oxygen face mask are limited to lower flow rates (up to 10 L/min) in part because the gas is cold and dry making tolerability a significant issue. These lower flow rates also limit FiO2 delivery and accuracy and aren’t high enough to offer the benefits of dead-space washout and positive airway pressure.

Although an NHF device can deliver high levels of oxygen (up to 100% FiO2) it’s not specifically an oxygen delivery device. In fact, it can be, and is, often used without supplemental oxygen, i.e. with room air – 0.21 FiO2.

Typically, “high flow” refers to flow rates above 15 L/min of a fully humidified air and oxygen mix. These higher flow rates enable mechanisms that cold, dry oxygen alone cannot provide.

See the table below for a comparison of common COT devices and NHF.

Optiflow Nasal High Flow compared with traditional oxygen delivery systems

You might also be interested in