What is high-flow nasal cannula oxygen noninvasive ventilation (NIV)?

Updated: Jun 18, 2020
  • Author: Guy W Soo Hoo, MD, MPH; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Answer

Answer

As a result of prospective, randomized clinical trials, another option has emerged for the patient with hypoxemic respiratory failure. Heated, humidified, high-flow nasal cannula oxygen has been available for over a decade, but refinements and increasing clinical experience have made it a solid alternative for management that exists in the spectrum of options before noninvasive and invasive mechanical ventilation. This modality was initially developed for neonatal patients, and refinements have permitted its use in adults. Conventional oxygen therapy is not well tolerated at high flow rates because of problems with unheated and nonhumidified oxygen. The high-flow nasal cannula oxygen systems are able to heat and humidify, improving patient tolerance and comfort. The high flow rates have other advantages in that high flow rates minimize room air entrainment, thereby increasing the FIO2 that can be provided to patients; are able to wash out dead space carbon dioxide, improving the efficiency of oxygen delivery; and the increased flow rate translates into positive end-expiratory pressure (PEEP). The amount of PEEP provided is a function of the flow rate but falls somewhere in the range of 0.35-0.69 cm water for each 10 L/min of increased flow rate. [2] Therefore, while high-flow nasal cannula devices technically do not provide assisted support or augment inspired tidal volume as provided by the other forms of mechanical ventilation, the small amount of positive pressure provided does help reduce the work of breathing and improve breathing patterns similarly to that achieved with CPAP. An intact respiratory drive is required with this modality, which means that it is not suited for patients with hypoventilation or a blunted respiratory drive. It is reasonable to consider this modality as a method of providing low-level positive pressure. While this is not assisted ventilation, it is at its most rudimentary level, is a form of noninvasive ventilation.


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