High-flow nasal cannula in severe asthma exacerbations: current evidence and clinical perspectives.

The management of asthma exacerbations is well established, including inhaled short-acting β2-agonist administration, systemic corticosteroid therapy and supplemental oxygen. Severe asthma exacerbations (SAEs) nonresponsive to medical and O2 therapy may require mechanical ventilation via endotracheal intubation (ETI), evaluation and admission to the intensive care unit (ICU). However, up to 35% of intubated and ventilated patients die due to conventional mechanical ventilation (CMV)-related life-threatening complications (i.e. barotrauma, circulatory collapse, cardiac arrhythmias, acute coronary syndrome, atelectasis and pneumonia). Among noninvasive respiratory therapies, the effectiveness of noninvasive ventilation (NIV) in preventing clinical deterioration and CMV in the earlier phases of SAE remains controversial. Limited tolerance to mechanical ventilation represents a drawback that can compromise treatment success. The high-flow nasal cannula (HFNC) is a widely applied respiratory supportive tool for the management of several patterns and types of acute respiratory failure, with patient acceptance being a key point favouring its application. Despite a potential pathophysiological rationale, clinical data on the feasibility and effectiveness of HFNC in SAEs are lacking. We conducted this concise narrative review to summarise the physiological and clinical benefits of HFNC compared to conventional oxygen therapy (COT) in adult patients with SAEs, focusing on outcomes such as dyspnoea, comfort, lung gas exchange, facilitation of inhaled therapy, hospitalisations, ETI and ICU admission. According to available data, there is no evidence of either superiority or inferiority of HFNC versus COT in SAEs. Further larger randomised control trials are required to define the role of HFNC in asthmatic attacks.