Airway and Transpulmonary Driving Pressure by End-Inspiratory Holds During Pressure Support Ventilation.

BACKGROUND: The precision of quasi-static airway driving pressure (DP) assessed in pressure support ventilation (PSV) as a surrogate of tidal lung stress is debatable because persistent muscular activity frequently alters the readability of end-inspiratory holds. In this study, we used strict criteria to discard excessive muscular activity during holds and assessed the accuracy of DP in predicting global lung stress in PSV. Additionally, we explored whether the physiological effects of high PEEP differed according to the response of respiratory system compliance (CRS). METHODS: Adults with ARDS undergoing PSV were enrolled. An esophageal catheter was inserted to calculate lung stress through transpulmonary driving pressure (DPL). DP and DPL were assessed in PSV at PEEP 5, 10, and 15 cm H2O by end-inspiratory holds. CRS was calculated as tidal volume (VT)/DP. We analyzed the effects of high PEEP on pressure-time product per minute (PTPmin), airway pressure at 100 ms (P0.1), and VT over PTP per breath (VT/PTPbr) in subjects with increased versus decreased CRS at high PEEP. RESULTS: Eighteen subjects and 162 end-inspiratory holds were analyzed; 51/162 (31.5%) of the holds had DPL 6 12 cm H2O. Significant association between DP and DPL was found at all PEEP levels (P < .001). DP had excellent precision to predict DPL, with 15 cm H2 O being identified as the best threshold for detecting DPL 6 12 cm H2O (area under the receiver operating characteristics 0.99 [95% CI 0.98--1.00]). CRS changes from low to high PEEP corresponded well with lung compliance changes (R2 0.91, P < .001) When CRS increased, a significant improvement of PTPmin and VT/PTPbr was found, without changes in P0.1. No benefits were observed when CRS decreased. CONCLUSIONS: In subjects with ARDS undergoing PSV, high DP assessed by readable end-inspiratory holds accurately detected potentially dangerous thresholds of DPL. Using DP to assess changes in CRS induced by PEEP during assisted ventilation may inform whether higher PEEP could be beneficial. [ABSTRACT FROM AUTHOR]