Esophageal pressure as a surrogate of pleural pressure in mechanically-ventilated patients

Background Esophageal pressure (P_es) is used to approximate pleural pressure (P_PL) and therefore to estimate transpulmonary pressure (P_L).

Objectives We aimed to compare esophageal and regional pleural pressures and to calculate transpulmonary pressures in a prospective physiological study on lung transplant recipients during their stay in the intensive care unit of a tertiary university hospital.

Methods Lung transplant recipients receiving invasive mechanical ventilation and monitored by esophageal manometry and dependent and non-dependent pleural catheters were investigated during the post-operative period. We performed simultaneous short time measurements and recordings of esophageal manometry and pleural pressures. Expiratory and inspiratory P_L were computed by subtracting regional P_PL or P_es from airway pressure; inspiratory P_L was also calculated with the elastance ratio method.

Results Sixteen patients were included. Among them, 14 were analyzed. Esophageal pressures correlated with dependent and non-dependent pleural pressures during expiration, respectively R²=0.71, p=0.005 and R²=0.77, p=0.001 and during inspiration, respectively, R²=0.66 for both (respectively p=0.01 and p=0.014). P_L calculated using P_es were close to those obtained from the dependent pleural catheter but higher than those obtained from the non-dependent pleural catheter both during expiration and inspiration.

Conclusion In ventilated lung transplant recipients, esophageal manometry is well correlated to pleural pressure. Absolute value of P_es is higher than pleural pressure of non-dependent lung regions and could therefore underestimate the highest level of lung stress in these at high risk of overinflation.