The influence of transpulmonary pressure on pulmonary vascular resistance -a physiological study using echocardiography during CPAP

Higher levels of PEEP are suspected to induce right heart dysfunction due to increased pulmonary vascular resistance (PVR). A U-shaped correlation of PVR and lung volume has been shown in animal models, with PVR increasing with lower and higher lung volumes. This physiological study aims to investigate the relation of transpulmonary pressure and PVR. Recruited healthy subjects underwent mask continuous airway pressure (CPAP), while esophageal manometry and echocardiographic assessment of PVR were performed. Of 43 screened subjects, 20 were identified in whom echocardiographic estimation of PVR was possible. During CPAP, echocardiographic PVR was lowest when transpulmonary pressures were close to 0 mbar, and increased as transpulmonary pressures became more positive, with a positive monotonic correlation (<i>ρ</i> = 0.337, p = 0.012). PVR with a transpulmonary pressure of 0 mbar was similar to PVR without CPAP (1.4 WU (IQR 1.3-1.5) versus 1.2 WU (IQR 1.2-1.5), p = 0.069). Our findings suggest that PVR could be lowest when airway pressure does not exceed intrathoracic pressure. Future studies should investigate this relationship in ventilated patients. Echocardiography might be suitable to monitor PVR in the presence of sufficiently traceable tricuspid regurgitation, however validation in ventilated patients is needed to determine clinical applicability.