Physics

Internal medicine

Diaphragm (acoustics)

Lung volumes

Pressure support ventilation

Airway

Engineering

Cardiology

Loudspeaker

Respiratory physiology

Ventilation (architecture)

Acoustics

Mean airway pressure

Mechanical ventilation

Tidal volume

Lung

Peak inspiratory pressure

Transpulmonary pressure

Cohort

Anesthesia

Respiratory system

Medicine

Mechanical engineering

Critical Care

Background Excessive 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 (Δ P occ ) could be used as a highly feasible non-invasive technique to screen for these conditions. Methods Respiratory muscle pressure ( P mus ), dynamic transpulmonary driving pressure (Δ P L,dyn , the difference between peak and end-expiratory transpulmonary pressure), and Δ P occ were measured daily in mechanically ventilated patients in two ICUs in Toronto, Canada. A conversion factor to predict Δ P L,dyn and P mus from Δ P occ was derived and validated using cross-validation. External validity was assessed in an independent cohort (Nanjing, China). Results Fifty-two daily recordings were collected in 16 patients. In this sample, P mus and Δ P L were frequently excessively high: P mus exceeded 10 cm H 2 O on 84% of study days and Δ P L,dyn exceeded 15 cm H 2 O on 53% of study days. Δ P occ measurements accurately detected P mus &gt; 10 cm H 2 O (AUROC 0.92, 95% CI 0.83–0.97) and Δ P L,dyn &gt; 15 cm H 2 O (AUROC 0.93, 95% CI 0.86–0.99). In the external validation cohort ( n = 12), estimating P mus and Δ P L,dyn from Δ P occ measurements detected excessively high P mus and Δ P L,dyn with similar accuracy (AUROC ≥ 0.94). Conclusions Measuring Δ 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.

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