A novel non-invasive method to detect excessively high respiratory effort and dynamic transpulmonary driving pressure during mechanical ventilation

BackgroundExcessive respiratory muscle effort during mechanical ventilation may cause patient self-inflicted lung injury and load-induced diaphragm myotrauma, but there are no non-invasive methods to reliably detect elevated transpulmonary driving pressure and elevated respiratory muscle effort during assisted ventilation. We hypothesized that the swing in airway pressure generated by respiratory muscle effort under assisted ventilation when the airway is briefly occluded (Delta P-occ) could be used as a highly feasible non-invasive technique to screen for these conditions.MethodsRespiratory muscle pressure (P-mus), dynamic transpulmonary driving pressure (Delta P-L,P-dyn, the difference between peak and end-expiratory transpulmonary pressure), and Delta P-occ were measured daily in mechanically ventilated patients in two ICUs in Toronto, Canada. A conversion factor to predict Delta P-L,P-dyn and P-mus from Delta P-occ was derived and validated using cross-validation. External validity was assessed in an independent cohort (Nanjing, China).ResultsFifty-two daily recordings were collected in 16 patients. In this sample, P-mus and Delta P-L were frequently excessively high: P-mus exceeded 10cm H2O on 84% of study days and Delta P-L,P-dyn exceeded 15cm H2O on 53% of study days. Delta P-occ measurements accurately detected P-mus >10cm H2O (AUROC 0.92, 95% CI 0.83-0.97) and Delta P-L,P-dyn>15cm H2O (AUROC 0.93, 95% CI 0.86-0.99). In the external validation cohort (n=12), estimating P-mus and Delta P-L,P-dyn from Delta P-occ measurements detected excessively high P-mus and Delta P-L,P-dyn with similar accuracy (AUROC >= 0.94).ConclusionsMeasuring Delta P-occ enables accurate non-invasive detection of elevated respiratory muscle pressure and transpulmonary driving pressure. Excessive respiratory effort and transpulmonary driving pressure may be frequent in spontaneously breathing ventilated patients.