Bedside Estimate of Mechanical Power (Part 3): Power Intensity and Mortality Across Berlin Definitions of ARDS Severity

Background: Mechanical power (W) is ventilator energy transferred to the respiratory system (ie, WRS) over time (J/min). WRS > 12 J/min and > 25 J/min are associated with ventilator-induced lung injury (VILI) onset and severe VILI respectively.1 Yet, baseline WRS of ∼ 28 J/min previously was not found to differentiate ARDS survivors from non-survivors.2 This retrospective study examined whether increasing WRS and WL intensity corresponds with increasing mortality as ARDS intensity worsens. Methods: 948 ARDS subjects were studied who: 1) met the Berlin definition, 2) were managed with ARDSNet protocols initiated ≤ 24 h after ARDS onset, 3) survived ≥ 24 h after protocol initiation. A simplified WRS calculation (0.098 x frequency x VT x [PEEP + PDR]),2 was used wherein WL was estimated using fractional subcomponents respiratory system elastance: EL/ERS (0.72).3 Data were analyzed using the Mann-Whitney test. Alpha was set at 0.05. Results: Within ∼36-48 h of ARDS onset, significantly higher WRS and WL were observed in non-survivors with median WRS approximating levels associated with severe VILI (ie, ∼25 J/min). Hospital mortality rates were similar to Berlin Taskforce findings (ie, 27%, 32%, and 45%).4 Lower estimates of WL also reached the threshold wherein some degree of VILI appeared likely. Conclusions: Contrary to previous findings,2 WRS ∼25 J/min was associated with increased mortality risk and, by extension, perhaps severe VILI risk.1. Silva PL et al. Anesthesiology 2020;132:949. 2. Wu H-P et al. Diagnostics 2023;13:1226. 3. Kallet RH et al. Respir Care 2007; 52(8):989. 4. Berlin Taskforce. JAMA 2012; 307:2526.Table 1BerlinPower(W) J/mSurvNon-SurvMortalityMildWrs18.5 (14.6-25)*24.7 (14.1-33.2) †26% WL13.3 (10.5-18)17.8 (10.1-23.9) † ModerateWrs21.3 (16.6-27.2)25.7 (19.7-34.5)‡32% WL15.4 (12-19.6)18.5 (14.1-24.9) ‡ SevereWrs23.5 (18.1-31.8)28.7 (15.6-27.9) ‖42% WL16.9 (13-22.9)20.6 (15.6-27.9) ‖ *data presented as median (IQR),† P=0.034, ‡ P<0.001, ‖ P=0.004