ABSTRACT
Background: Even if definitive evidence is still missing, prone position in non-intubated hypoxemic patients with Covid-19 is largely used. The aim of the present study was to investigate whether the amount and distribution of lung abnormalities evaluated by CT-scan can predict the improvement of oxygenation when Covid-19 patients undergoing non-invasive ventilation (NIV) are turned prone. Method(s): Retrospective monocentric study of severe Covid-19 patients who underwent NIV and prone position, evaluated with a basal chest CT-scan. Result(s): Forty-five severe Covid-19 patients were considered. On average 50% of the overall lung volume was involved by pneumonia at CT-scan, with ground glass, and consolidation accounting for 44, and 4%, respectively. The parenchymal abnormalities were predominantly posterior, as demonstrated by a posterior/anterior ratio of ground glass and consolidation of 1.5, and 4.4, respectively. PaO2/FiO2, whose basal value under NIV in supine position was 140 [IQR 108;169] improved on average by 67% (+98) during prone position. Once supine position was resumed, improvement in oxygenation was maintained in 28 patients (62% of the overall population, categorized as "responders"). We did not find significant difference between responders and non-responders in terms of the amount and distribution of parenchymal abnormalities. No correlation emerged between the distribution of parenchymal abnormalies and changes in oxygenation in supine position before and after prone position (R2 = 0.009, p= 0.526). Conclusion(s): the amount and distribution of lung abnormalities evaluated by CT-scan do not predict the response to awake prone position in patients with severe Covid-19 pneumonia undergoing non-invasive ventilation.