Esophageal pressures in supine and prone position: evaluation using high-resolution manometry

Esophageal pressure (PES), used as a substitute for pleural pressure in calculations of respiratory mechanics, are complex and influenced by several factors. High-resolution manometry (HRM) provides pressure readings over the esophageal length, which makes it possible to identify factors other than respiratory mechanics that influence esophageal pressure. The aim of this study was to describe and explore esophageal pressure in prone and supine position at different ventilatory settings. PES was measured using HRM in 20 mechanically ventilated patients before start of spinal surgery. PEEP of 5 and 12 cmH₂O were used in supine and prone position while data were recorded continuously. Mean end-expiratory (PES_EE) and tidal variation of esophageal pressures (ΔPES) from sensors in different esophageal regions were compared including a selection of sensors with theoretically optimal pressure readings (PES_OPT). PES_EE was significantly lower (MD 3.2-5.7), ΔPES was significantly higher (MD 0.8-1.6 cmH₂O) and cardiac oscillations were significantly smaller in prone compared to supine position. Differences were dependent on PEEP level and regions of esophagus included. Mean within patient variability of PES_EE and ΔPES was 38-540% depending on PEEP level and body position. End-expiratory PES_OPT was lower than mean PES_EE from larger esophageal regions and less variable. A large variation in PES is seen in both supine and prone position but depends on which sensors are included in calculations of PES. There are significant differences in absolute pressures and in influence from mediastinal organs between supine and prone position.