Lung recruitment and hyperinflation with higher positive end-expiratory pressure in COVID-19: a computed tomography study

Abstract

Abstract Background A higher (> 10 cmH2O) positive end-expiratory pressure (PEEP) is commonly used in patients with moderate to severe hypoxemia due to the novel coronavirus disease (COVID-19). However, compliance more commonly decreases when PEEP is increased from 10 to 15 cmH2O, as for lung hyperinflation. In this study, we directly measured lung recruitment and hyperinflation induced by increasing PEEP from 10 to 15 cmH2O in mechanically ventilated patients with COVID-19. Methods Twenty mechanically ventilated patients with COVID-19 underwent a lung computed tomography (CT) at 10 and 15 cmH2O of airway pressure. Gas exchange and compliance were then measured with 10 and 15 cmH2O of PEEP. Recruitment was computed as the decrease of the non-aerated lung volume (density above − 100 HU) and hyperinflation as the increase of the over-aerated lung volume (density below − 900 HU). If recruitment was larger than hyperinflation, the net morphological response was “recruitment”; otherwise, it was “hyperinflation”. Results With 10 cmH2O of PEEP, the median (Q1-Q3) arterial tension to the inspiratory fraction of oxygen (PaO2:FiO2) was 146 (107–197) mmHg. The net morphological response to increasing PEEP was recruitment in nine (45%) patients and hyperinflation in eleven (55%). Oxygenation improved in twelve (60%) patients, but compliance in only three (15%). Compliance with 10 cmH2O of PEEP ≤ 45 cmH2O/ml predicted net recruitment in response to increasing PEEP with a positive predictive value of 0.89 (95%-confidence intervals: 0.49-1.00) and a negative predictive value of 0.91 (0.59-1.00). Conclusions The morphological response to a higher PEEP is largely variable in patients with COVID-19, ranging from net recruitment (in half of the patients) to net hyperinflation (in the other half). Baseline compliance may help to predict the individual response to increasing PEEP.