Characteristics and risk factors associated with mortality during the first cycle of prone secondary to ARDS due to SARS-CoV-2 pneumonia

Objective: To analyze characteristics, changes in oxygenation, and pulmonary mechanics, in mechanically ventilated patients with ARDS due to SARS-CoV-2 treated with prone position and evaluate the response to this maneuver. Design: Cohort study including patients with PaO2/FiO(2) <150 mmHg requiring prone position over 18 months. We classified patients according to PaO2/FiO(2) changes from basal to 24 h after the first prone cycle as: 1) no increase 2) increase <25%, 3) 25%-50% increase 4) increase >50%. Setting: 33-bed medical-surgical Intensive Care Unit (ICU) in Argentina. Patients: 273 patients. Interventions: None. Main variables of interest: Epidemiological characteristics, respiratory mechanics and oxygenation were compared between survivors and non-survivors. Independent factors associated with in-hospital mortality were identified. Results: Baseline PaO2/FiO(2) was 116 [97-135] mmHg (115 [94-136] in survivors vs. 117 [98-134] in non-survivors; p = 0.50). After prone positioning, 22 patients (8%) had similar PaO2/FiO(2) values; 46(16%) increased PaO2/FiO(2) <= 25%; 55 (21%) increased it 25%-50%; and 150 (55%), >50%. Mortality was 86%, 87%, 72% and 50% respectively (p < 0.001). Baseline PaO2/FiO(2,) <100 mmHg did not imply that patients were refractory to prone position. Factors independently associated with mortality were age, percentage increase in PaO2/FiO(2) after 24 h being in prone, and number of prone cycles. Conclusions: Older patients unable to improve PaO2/FiO(2) after 24 h in prone position and who require >1 cycle might early receive additional treatments for refractory hypoxemia. After the first 24 h in the prone position, a low percentage of PaO2/FiO(2) increase over baseline, beyond the initial value, was independently associated with higher mortality.