Physiological effects and clinical evidence of high-flow nasal cannula during acute exacerbation in COPD patients: A narrative review.

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death worldwide. During severe exacerbations, COPD patients may develop acute respiratory failure (ARF), often necessitating hospital admission due to impaired gas exchange. In COPD patients, the diaphragm is subjected to an increased workload resulting from airflow limitations and geometric changes in the thorax due to pulmonary hyperinflation. Noninvasive ventilation (NIV) plays a crucial role in managing type II ARF by improving alveolar ventilation, reducing the work of breathing, minimizing the need for endotracheal intubation (ETI), and decreasing both hospital stays and mortality rates. Studies have shown that approximately 64% of patients with acute exacerbation of COPD (AECOPD) may fail NIV, primarily due to worsening respiratory function, interface intolerance, cardiovascular instability, or neurological deterioration. For patients intolerant to NIV, a trial with a high-flow nasal cannula (HFNC) is recommended. Recently, HFNC has gained popularity as a novel respiratory support system and is increasingly used in routine clinical practice for AECOPD patients. It delivers warmed, humidified, and oxygen-enriched air through a nasal cannula at flow rates of up to 60 L/min. This narrative review aims to describe the physiological effects of HFNC in the COPD population and provide an updated overview of HFNC's role in AECOPD patients requiring hospitalization.