Gas Exchange of prone positioning in influenza pneumonia-related acute respiratory distress syndrome: A multicenter retrospective cohort study in Taiwan

Abstract Background: Prone positioning has demonstrated decreased mortality in severe acute respiratory distress syndrome (ARDS) patients. The aim of this study was to investigate the effect of prone positioning in patients with influenza pneumonia-related severe ARDS. Methods: This retrospective study includes eight tertiary referral centers. All the patients with influenza pneumonia induced severe ARDS and receiving prone positioning were enrolled. Demographic data, laboratory data, treatment record, ventilator setting data and outcomes were collected. PaO2 responders were defined as the PaO2/FiO2 ratio increasing by ≥20% or ≥20 mm Hg, while PaCO2 responders were defined as PaCO2 decreasing by ≥1 mm Hg after prone positioning for one day. Results: Sixty-five patients receiving prone positioning were enrolled, with 37 (57%) were PaO2 responders and 33 (51%) were PaCO2 responders. Mortality rates were not significantly different between responders and non-responders. PaCO2 responder survivors had significantly shortened length of stay at the ICU (21.0 ± 13.5 vs. 31.7 ± 18.5 days, P = 0.038) and hospital (30.2 ± 16.6 vs. 43.0 ± 16.3 days, P = 0.013) than did non-responders. Multivariate analysis revealed younger age (odds ratio 0.903, 95% confidence interval 0.824-0.989; P = 0.028) and higher PaCO2 level before prone positioning (odds ratio 1.121 confidence interval 1.020-1.231; P = 0.017) were the predictors of PaCO2 responders. Conclusions: In this multicenter retrospective cohort study of influenza pneumonia patients with severe ARDS receiving prone positioning, PaCO2 responders had modestly better clinical outcomes. Younger age and higher PaCO2 level before prone positioning were the predictors of PaCO2 responders. Keywords: Prone positioning, Acute Respiratory Distress Syndrome, Influenza, Gas exchange, Outcome