CPAP-associated changes in oxygenation and clinical outcomes in severe COVID-19 pneumonia

ABSTRACT

Background: Continuous positive airway pressure (CPAP) can improve oxygenation in severe COVID-19 pneumonia. Objective(s) To assess whether CPAP-associated improvements in oxygenation can inform clinical outcomes in patients with severe COVID-19 pneumonia. Method(s) Retrospective study in patients with severe COVID-19 pneumonia treated with CPAP in three academic respiratory units in Milan, Italy. Arterial gas analysis obtained before and 1 hour after starting CPAP. CPAP failure defined as either death in the respiratory units while on CPAP or need for intubation. Result(s) 211 patients (mean age 64 years, 74% males) were included. Baseline median PaO2was 68 (57-83) mmHg, PaO2/FiO2(P/F) ratio was 129 (91-179) mmHg and alveolar-arterial (A-a) O2 gradient was 310 (177-559) mmHg. On CPAP, PaO2and P/F increased to 100 (79-141) (p<0.001) and 195 (132-257;p<0.001) mmHg and A-a gradient decreased to 240 (188-308;p<0.001) mmHg. 42 (19.9%) patients died in the respiratory units while on CPAP and 51 (24.2%) required intubation. There was a substantial overlap of baseline and CPAP-associated values of PaO2, P/F ratio and A-a gradient in CPAP failures and successes (Figure). CPAP-associated changes in PaO2, P/F ratio and A-a gradient in both groups were similar. Conclusion(s) CPAP-associated improvements in oxygenation cannot be used to inform clinical outcomes of the individual patient with severe COVID-19 pneumonia.