Prone position and the risk of venous thrombosis in COVID-19 patients with respiratory failure

Several lines of evidence attest that ventilation in prone position may significantly improve lung function in critically ill patients with acute respiratory distress syndrome (ARDS) due to the more uniform distribution of tidal volume and improved recruitment, which contribute to ameliorate the ventilation–perfusion ratio.[1] Nevertheless, the overall clinical benefit of long periods of pronation over the supine position during mechanical ventilation remains controversial, even in patients with coronavirus disease 2019 (COVID-19)-related ARDS.[1] A recent meta-analysis of seven retrospective cohort studies including 5216 COVID-19 patients concluded that intensive care unit (ICU) mortality was higher in the prone position, while no significant differences were found in terms of cumulative or hospital mortality, length of stay in the ICU, and duration of mechanical ventilation between prone and supine positions.[2] In addition, there is evidence that the prone position may have several adverse side effects, some of which are clearly acknowledged (e.g., pressure ulcers, nerve injury, bleeding, displacement of medical devices, etc.),[3] while others are often overlooked. The risk of developing venous thromboembolism (VTE) in prone patients who are already at increased risk of thrombosis due to COVID-19 is one such underestimated complication.