Abstract
Background: The prone position and lung protective ventilation are the only interventions to improve survival in ARDS patients. Due to early reports during the COVID-19 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 whether titration of ventilation should be reassessed when the patient is repositioned. To our knowledge, respiratory compliance (CRS) comparisons during supine and prone positions have been described in patients only at predefined levels of PEEP. Therefore, the objective of this study was to characterize the response of respiratory mechanics in supine and prone positions during a decremental PEEP trial in COVID-19 related ARDS patients.
Methods: We studied a cohort of patients with COVID-19 related ARDS undergoing invasive mechanical ventilation. The study was approved by the local IRBs. Patients were ventilated with a tidal volume of 5–6 mL/kg PBW. A decremental PEEP trial was performed. Airway pressures and flow were recorded in supine and prone positions to calculate CRS. Ventilation distribution was measured by electrical impedance tomography (EIT) in three gravitational regions (ROI).
Results: We included 14 patients with COVID-19 related ARDS. The cohort’s median age was 65 y (IQR 59–69) with a BMI of 32.5 (IQR 28–35). After 24 h of intubation, median PaO2/FIO2 was 151 mm Hg (IQR 105–170) and PEEP was 10 cm H2O (IQR 10–14). Figure 1-A, B, and C illustrate, respectively, patients whose maximum CRS was reduced, similar, or increased after pronation at a certain level of PEEP. The PEEP to obtain the maximum CRS was lower in prone compared to supine position in 14/20 (70%) patients (Figure 1-D). Changes in CRS after pronation had symmetrical distribution (Figure 1-E). The maximum CRS was reached with higher ventilation distribution in the non-dependent zone in prone position (~35%).
Conclusions: In a cohort of mechanically ventilated patients with severe COVID-19 related ARDS, a subset of patients demonstrated a marked improvement in lung mechanics after pronation, with a resultant best PEEP for the highest compliance being lower in prone versus supine. Ventilation distribution was shifted to dorsal-predominant from ventral-predominant in prone position and correlates with changes in CRS. These results suggest that PEEP titration would be prudent to perform after prone positioning.
Footnotes
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