Non-invasive ventilation during severe asthma exacerbation: physiological rationale, current evidence, and practical approach.

Severe asthma exacerbation (SAE) is characterized by acute airflow obstruction, dynamic hyperinflation, and marked increases in inspiratory effort and work of breathing. Although pharmacological therapy remains the cornerstone of treatment, its effects on the mechanical consequences of severe airway obstruction may be delayed. During this interval, progressive respiratory muscle overload may contribute to worsening gas exchange, hemodynamic compromise, and, ultimately, the need for invasive mechanical ventilation. Non-invasive ventilation (NIV) has a strong physiological rationale in this setting. By partially counterbalancing intrinsic positive endexpiratory pressure, NIV may reduce inspiratory threshold load, unload the respiratory muscles, and transiently limit dynamic hyperinflation while pharmacological therapy takes effect. Small randomized and observational studies suggest that NIV may transiently improve respiratory distress and gas exchange in selected patients. However, the available evidence remains limited, heterogeneous, and highly susceptible to selection bias; therefore, NIV cannot currently be recommended routinely in SAE. This review summarizes the pathophysiological basis, available clinical evidence, and practical aspects of NIV use in SAE, with particular attention to patient selection, timing of initiation, ventilator settings, aerosol delivery, and monitoring.