Spontaneous pneumomediastinum: a surrogate of P-SILI in critically ill COVID-19 patients

Abstract

Spontaneous pneumomediastinum (SP) was described early during the COVID-19 pandemic in large series of patient with severe pneumonia, but all partly involved patients with invasive mechanical ventilation (IMV) at the time of SP diagnosis. We aimed, in this retrospective multicenter observational study, to describe the prevalence and outcomes of SP during severe COVID-19 pneumonia before any IMV, in order to rule out mechanisms induced by IMV in the development of pneumomediastinum. A total of 551 patients were included. Twenty-one (4%) developed a SP while under non-invasive respiratory support, with a median of 6 days [4–12] from ICU admission. Although the proportion of patients eventually requiring IMV was similar, time to tracheal intubation was longer in patients with SP (6 days [4–13] vs. 2 days [1–4]; P = 0.0001), with a higher first-line use of non-invasive ventilation (n = 11; 52% vs. n = 150; 28%). By focusing on the 21 patients who developed a SP we noticed persisting signs of severe lung disease and respiratory failure with lower ROX index between admission and occurrence of SP (3.94 [3.15–5.55] at ICU admission vs. 3.25 [2.73–4.02] the day preceding SP; P = 0.1) which may underlie potential indirect signals of patient-self inflicted lung injury (P-SILI). In this series of critically-ill COVID-19 patients, prevalence of SP without invasive mechanical ventilation was not uncommon, affecting 4% of patients and was associated with higher need for vital supports and longer ICU length of stay. One pathophysiological mechanism may potentially be carried-out by P-SILI related to a prolonged respiratory failure as underlined by a delayed use of IMV and the evolution of ROX index between ICU admission and the day preceding SP.