Clinical Research Directory

Inclusion Criteria: * more than 18 years old * needing High-flow Nasal Cannula oxygenation therapy Exclusion Criteria: * received mechanical ventilation, including invasive or noninvasive ventilation within one month prior to enrollment * history of neuromuscular disorders (e.g., myasthenia gravis, Guillain-Barre syndrome); * immediate endotracheal intubation is required (life-threatening hypoxemia) * extensive damage to the thoracic skin (e.g., burns) unable to undergo ultrasonography * pregnancy * attending physician deemed it inappropriate to participate in the trial.