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

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.

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 (PTP_mus/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 PTP_mus/min > 200 and < 50 cmH₂O s min^-1, respectively.

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 PTP_mus/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 PTP_mus/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).

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.