Titration of Mechanical Ventilation in Supine Compared to Prone Position Reveals Different Respiratory Mechanics Behavior in Covid19 Patients

Abstract

INTRODUCTION: The prone position and protective lung ventilation are the only interventions to improve survival in Acute Respiratory Distress Syndrome (ARDS) patients. Due to early reports during the COVID-pandemic showing dramatic improvements in oxygenation, the use of prone position has been broadly adopted in intubated patients around the globe. However, it remains unclear on whether titration of ventilation should be reassessed when the patient is repositioned. Therefore, the objective of this study was to characterize the response of respiratory mechanics in supine and prone positions during a decremental end-expiratory positive pressure trial in COVID-19 related ARDS patients. METHODS: This is a retrospective analysis of patients with COVID-19 related ARDS under invasive mechanical ventilation in supine and prone positions. The study was approved by the Investigational Review Board at the Massachusetts General Hospital and by the Ethics and Research Committee at Heart Institute (InCor) from the University of São Paulo. Prone position was recommended based on hypoxia, measured as PaO2/FIO2 ratio (< 150 mmHg). Patients were sedated, and under volume-controlled ventilation (5-6 mL/Kg PBW). Airway pressure, flow, esophageal pressure and electrical impedance tomography (EIT) were recorded. A decremental PEEP trial was performed on supine and prone position. RESULTS: We included 10 patients with COVID-19 related ARDS. Median age was 62 years (range, 35-72), 5 patients (50%) were female, and BMI was 35 (range, 27-46). After 24 hours of intubation, median PaO2/FIO2 was 174 mmHg (IQR, 166-192), PEEP was 10 cmH2O (IQR, 10-14.5), and static compliance of respiratory system (CRS) was 28.5 mL/cmH2O (IQR, 24.2-35.7). The time interval between intubation and the supine-prone assessment was 7 days (IQR, 5-10). During the supine/prone assessment, a variety of CRS responses were observed among patients (Figure 1). Overall, the highest CRS was 44 mL/cmH2O (IQR, 29-57) in supine and 52 mL/cmH2O (IQR, 39-67) in prone position. At the highest CRS, from supine to prone position: lung compliance (CL) increased by 15 mL/cmH2O (IQR, 13-31), suggesting lung recruitment, and chest wall compliance (CCW) was reduced by 28 ml/cmH2O (IQR, 14-48) indicating external compression of the chest;and end-expiratory transpulmonary pressure (PLend-exp) increased from-3.4 cmH2O (IQR,-4.6 to-2.5) to 0.4 cmH2O (IQR, 0.1-3.0) suggesting decreased pleural pressure. CONCLUSION: Patients with COVID-19 related ARDS assessed in supine and prone positions revels a variety response to prone position on CRS during decremental PEEP trial, suggesting the necessity to reassess the PEEP when the patient is repositioned. (Table Presented).