Performance of noninvasive airway occlusion maneuvers to assess lung stress and diaphragm effort in mechanically ventilated critically ill patients


 
 Monitoring and controlling lung stress and diaphragm effort has been hypothesized to limit lung injury and diaphragm injury. The occluded inspiratory airway pressure (Pocc) and the airway occlusion pressure at 100ms (P0.1) have been used as non-invasive methods to assess lung stress and respiratory muscle effort, but comparative performance of these measures and their correlation to diaphragm effort is unknown. We hypothesized that Pocc and P0.1 correlate to diaphragm effort and lung stress, and would have strong discriminative performance in identifying extremes of lung stress and diaphragm effort.
 
 
 
 Secondary analysis of two studies. Transdiaphragmatic pressure (ΔPdi) and transpulmonary pressure (ΔPL) were obtained with double-balloon nasogastric catheters in critically ill patients (n = 38). Pocc and P0.1 were measured every 1-3 hours. Correlations between Pocc and P0.1 with ΔPL and ΔPdi were computed from patients from the first cohort. Accuracy of Pocc and P0.1 to identify patients with extremes of lung stress (ΔPL>20cmH2O) and diaphragm effort (ΔPdi <3cmH2O and >12cmH2O) in the preceding hour was assessed with area under receiver-operator characteristic curves (AUROC). Cut-offs were validated in patients from the second cohort (n = 13).
 
 
 
 Pocc and P0.1 correlate with ΔPL (r2=0.62 and 0.51, respectively) and ΔPdi (r2 = 0.53 and 0.22, respectively). AUROC to detect high lung stress is 0.90 (0.86–0.94) for Pocc and 0.88 (0.84-0.92) for P0.1. AUROC to detect low diaphragm effort is 0.97 (0.87–1.00) for Pocc and 0.93 (0.81–0.99) for P0.1. AUROC to detect high diaphragm effort is 0.86 (0.81–0.91) for Pocc and 0.73 (0.66-0.79) for P0.1. Performance was similar in the external dataset.
 
 
 
 Pocc and P0.1 correlate with lung stress and diaphragm effort in the preceding hour. Diagnostic performance of Pocc and P0.1 to detect extremes in these parameters is reasonable to excellent. Pocc is more accurate in detecting high diaphragm effort.
