Inefficient humidification as the cause of noninvasive ventilation failure in COVID-19 patients

摘要

Five to six percent of COVID-19 patients developed acute hypoxemia respiratory failure. 1 The hypoxemia might not respond to high-flow nasal cannula therapy (HFNC), and eventually require escalation of oxygen therapy to con- tinuous positive airway pressure (CPAP) or noninvasive ventilation (NIV). Patients who failed NIV had high minute ventilation, which may be due to increased alveolar dead space, increased CO2 production from the inflammatory response and impaired carbon dioxide clearance, or both. 2 Successful NIV leads to more patient comfort, reduced ven- tilatory work of breathing, decreased chest wall motion and minute ventilation, improvement in arterial oxygen satu- ration, and dyspnea resolution. Patients on NIV frequently complain of dry mouth. Because of ineffective humidifica- tion and high minute ventilation, COVID-19 patients develop dry and thick bronchial secretions, which might lead to air- way obstruction. This also results in increased requirements of airway procedure like bronchoscopy or endotracheal tube replacement in COVID-19 patients. There is lack of clear guideline or recommendation regarding the appropri- ate humidification application during NIV, as this is poorly understood.