Reproducible determination of transpulmonary pressures

Oesophageal pressures, as measured in an oesophageal balloon catheter, are a validated substitute for pleural pressures. Transpulmonary pressures, indispensable to improve our understanding of ventilatory physiology, are therefore typically calculated as the difference between airway and oesophageal pressures. The oesophageal pressure signal, however, features a superimposed oscillation due to cardiac motion, not representative for pleural pressure. Additionally, oesophageal contractions or surgical manipulation can alter the signal. In practice, transpulmonary pressures are therefore manually determined from the pressure-time graphic by visual inspection of the waves and averaging a limited number of samples. We suggest an approach to extract the end-expiratory transpulmonary pressure from the raw monitoring data. • Our approach reproducibly determines end-expiratory transpulmonary pressures at a given level of set positive end-expiratory pressure at the ventilator. • Our approach ignores surgical disturbance and cardiac oscillations in the oesophageal pressure signal.