Inhomogeneity of regional ventilation during awake pronation with helmet CPAP in COVID-19 ARDS patients

Abstract

Introduction: prone positioning with continous positive airway pressure (CPAP) is widely used for respiratory support in awake patients with COVID-19 associated acute respiratory failure. We aimed to assess the respiratory mechanics and distribution of ventilation in COVID-19 associated ARDS treated by CPAP in awake prone position. Methods: we studied sixteen awake COVID-19 patients with moderate to severe ARDS. The study protocol consisted of a randomized sequence of supine and prone position with imposed PEEP of 5 and 10 cmH2O delivered by helmet CPAP. Respiratory mechanics and distribution of ventilation were assessed through esophageal pressure (PES) and electrical impedance tomography (EIT). At the end of each 20 minutes phase, arterial blood gas analysis was performed, and PES swing and EIT tracings were recorded for the calculation of the respiratory mechanics and regional ventilation. Results: the patient’s position had no significant effects on respiratory mechanics. EIT analysis did not detect differences among global indices of ventilation. A significant proportion of pixel in the sternal region of interest showed increase of compliance from supine to prone position and PaO2/FIO2 increased accordingly. The best improvement of both PaO2/FIO2 and sternal compliance was obtained in prone position with PEEP 10 cmH2O. Conclusions: in the studied subjects, prone positioning during CPAP treatment raised oxygenation without improvement of “protective” ventilation or of global ventilatory inhomogeneity indices. Prone positioning with higher PEEP significantly increased the recruitment of sternal regions.