Use of airway pressure-based indices to detect high and low inspiratory effort during pressure support ventilation: a diagnostic accuracy study

Abstract

Background: Assessment of the patient’s respiratory effort is essential during assisted ventilation. We aimed to evaluate the accuracy of airway pressure (P aw)-based indices to detect potential injurious inspiratory effort during pressure support (PS) ventilation. Methods: In this prospective diagnostic accuracy study conducted in four ICUs in two academic hospitals, 28 adult acute respiratory failure patients undergoing PS ventilation were enrolled. A downward PS titration was conducted from 20 cmH2O to 2 cmH2O at a 2 cmH2O interval. By performing an end-expiratory airway occlusion maneuver, the negative P aw generated during the first 100 ms (P 0.1) and the maximal negative swing of P aw (∆P occ) were measured. After an end-inspiratory airway occlusion, P aw reached a plateau, and the magnitude of change in plateau from peak P aw was measured as pressure muscle index (PMI). Esophageal pressure was monitored and inspiratory muscle pressure (P mus) and P mus–time product per minute (PTPmus/min) were used as the reference standard for the patient’s effort. High and low effort was defined as P mus > 10 and < 5 cmH2O, or PTPmus/min > 200 and < 50 cmH2O s min−1, respectively. Results: A total of 246 levels of PS were tested. The low inspiratory effort was diagnosed in 145 (59.0%) and 136 (55.3%) PS levels using respective P mus and PTPmus/min criterion. The receiver operating characteristic area of the three P aw-based indices by the respective two criteria ranged from 0.87 to 0.95, and balanced sensitivity (0.83–0.96), specificity (0.74–0.88), and positive (0.80–0.91) and negative predictive values (0.78–0.94) were obtained. The high effort was diagnosed in 34 (13.8%) and 17 (6.9%) support levels using P mus and PTPmus/min criterion, respectively. High receiver operating characteristic areas of the three P aw-based indices by the two criteria were found (0.93–0.95). A high sensitivity (0.80–1.00) and negative predictive value (0.97–1.00) were found with a low positive predictive value (0.23–0.64). Conclusions: By performing simple airway occlusion maneuvers, the P aw-based indices could be reliably used to detect low inspiratory efforts. Non-invasive and easily accessible characteristics support their potential bedside use for avoiding over-assistance. More evaluation of their performance is required in cohorts with high effort.