Abstract
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 (ΔPocc) could be used as a highly feasible non-invasive technique to screen for these conditions.MethodsRespiratory muscle pressure (Pmus), dynamic transpulmonary driving pressure (ΔPL,dyn, the difference between peak and end-expiratory transpulmonary pressure), and ΔPocc were measured daily in mechanically ventilated patients in two ICUs in Toronto, Canada. A conversion factor to predict ΔPL,dyn and Pmus from ΔPocc 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, Pmus and ΔPL were frequently excessively high: Pmus exceeded 10 cm H2O on 84% of study days and ΔPL,dyn exceeded 15 cm H2O on 53% of study days. ΔPocc measurements accurately detected Pmus > 10 cm H2O (AUROC 0.92, 95% CI 0.83–0.97) and ΔPL,dyn > 15 cm H2O (AUROC 0.93, 95% CI 0.86–0.99). In the external validation cohort (n = 12), estimating Pmus and ΔPL,dyn from ΔPocc measurements detected excessively high Pmus and ΔPL,dyn with similar accuracy (AUROC ≥ 0.94).ConclusionsMeasuring ΔPocc 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.
Highlights
Patient inspiratory effort during mechanical ventilation may have both beneficial and deleterious effects
The findings presented in this paper represent an ancillary analysis on an ongoing clinical study (MYOTRAUMA, ClinicalTrials.gov NCT03108118) characterizing diaphragm activity and function longitudinally during mechanical ventilation
Respiratory muscle pressure (Pmus) was higher under partially assisted modes and higher in patients admitted for pneumonia compared to patients with non-pulmonary admission diagnoses
Summary
Patient inspiratory effort during mechanical ventilation may have both beneficial and deleterious effects. Inspiratory effort increases tidal volume and global dynamic lung stress (quantified by transpulmonary driving pressure, ΔPL) in pressure-targeted modes of ventilation, potentially leading to lung injury. Vigorous inspiratory efforts can generate pendelluft and amplify regional lung stress and strain, causing regional lung injury even in volume-cycled modes of ventilation [1, 2]. The amplitude of this regional stress is reflected by the dynamic transpulmonary driving pressure, ΔPL,dyn [3]. 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 (ΔPocc) could be used as a highly feasible non-invasive technique to screen for these conditions
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