Fig. 2.

Patient flow diagram. *The three medical centers were Kyungpook National University Chilgok Hospital, Kyungpook National University Hospital and Pusan National University Hospital. ^†Some patients were excluded based on more than one factor. ^‡Severe illness – individuals with oxygen saturation (SpO₂) < 94% on room air at sea level, a ratio of arterial partial pressure of oxygen to fraction of inspired oxygen < 300 mmHg, respiratory frequency > 30 breaths/minute or lung infiltrates > 50%; and critical illness – individuals with respiratory failure, septic shock and/or multiple organ dysfunction. ^§SpO₂ is for use in patients with hypercapnic respiratory failure who have clinically recommended oxygen saturation of 88–92%. BMI, body mass index; SoC, standard of care. ^¶Patients without medical cost information were excluded from the medical utilization analysis.