High Flow Nasal Cannula Versus High Velocity Nasal Insufflation for Weaning

In intensive care units (ICUs), approximately 10% to 15%of patients ready to be separated from a ventilator experience extubation failure leading to reintubation. In patients considered at high risk, these rates can even exceed 20%. Because reintubation is associated with particularly high mortality a strategy of oxygenation aimed at avoiding reintubation deserves consideration. Although noninvasive ventilation may prevent postextubation respiratory failure in patients at high risk only 2 small-scale randomized clinical trials (RCTs) have shown decreased reintubation rates compared with standard oxygen. The most recent international clinical practice guidelines recommend the use of noninvasive ventilation to prevent post extubation respiratory failure in patients at high risk of extubation failure (7). However, up until now, no large-scale RCT has demonstrated a significant reduction of reintubation rates with noninvasive ventilation compared with standard oxygen. Thereby, most patients are treated with standard oxygen in clinical practice and only10% of them receive noninvasive ventilation after extubation in the ICU.

High-flow nasal cannula (HFNC) oxygen therapy is a new type of respiratory support system which can supply high flow mixed gases through special nasal prongs at a sufficient temperature and humidity for patient comfort. Many studies have confirmed that the comfort and tolerance of HFNC is significantly higher than that of NIV. As an alternative to NIV, HFNC has been shown to be as efficacious as NIV in preventing post-extubation respiratory failure or re-intubation in patients with hypoxemic respiratory failure.

High-velocity nasal insufflation, a form of high-flow nasal cannula, focuses on optimum efficiency of the dead-space purge to augment ventilation (removal of carbon dioxide from the dead space between breaths), in addition to providing other effects of high-flow nasal cannula. This is accomplished by use of small-bore nasal cannulae (typically 2.7-mm internal diameter for adult patients) to produce high velocity flow that is approximately 360% greater than that of the larger bore cannulae used in previous studies. According to flow analyses8 and clinical experience, high velocity nasal insufflation typically requires a flow of 25 to 35 L/min in adults to accomplish a complete purge of the extrathoracic anatomic reservoir between breaths.