A simple method of mechanical power calculation: using mean airway pressure to replace plateau pressure

The reference method for mechanical power (MP) calculation proposed by Gattinoni et al. is based on plateau pressure (Pplat) which needs an inspiratory hold. This study aims to introduce and validate a simple surrogate for MP calculation without any intervention in ventilated patients with or without acute respiratory distress syndrome (ARDS). The introduced equation is as:Pmean-derived MP=0.1×VE×[Pmean+(Pmean-PEEP)×Te/Ti]\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{P}}_{{{\text{mean}}}} {\text{-derived MP}} = 0.1 \times {\text{VE}} \times [{\text{P}}_{{{\text{mean}}}} + ({\text{P}}_{{{\text{mean}}}} - {\text{PEEP}}) \times {\text{T}}_{{\text{e}}} /{\text{T}}_{{\text{i}}} ]$$\end{document}where Pmean is mean airway pressure, VE is minute ventilation, PEEP is positive end-expiratory pressure, and Te/Ti is expiratory-to-inspiratory ratio. 50 patients with ARDS and 50 post-operative patients without ARDS were enrolled. Pmean-derived MP and reference MP were obtained at the inspiratory plateau time (Tplat) of 0 and 0.5 s (s). When Tplat was adjusted from 0 to 0.5 s, higher Pmean [non-ARDS cases: 9.3 (8.8–9.9) cmH2O versus 8.2 (7.9–8.8) cmH2O, P < 0.001; ARDS cases: 14 (13–16) cmH2O versus 13 (11–14) cmH2O, P < 0.001] and shorter Te/Ti [non-ARDS cases: 1.4 (1.2–1.7) versus 2.4 (2.0–3.0), P < 0.001; ARDS cases: 1.3 (1.2–1.5) versus 2.5 (2.3–2.9), P < 0.001] were found. At both Tplat levels, the Pmean-derived MP correlated well with the reference MP both in patients with or without ARDS (non-ARDS: slopes = 1.05, 0.94, R2 = 0.95, 0.93, bias + 0.76, + 0.51; ARDS: slopes = 1.03, 0.95, R2 = 0.96, 0.96, bias + 0.97, + 0.78. P < 0.0001 for all). In patients with or without ARDS, Pmean-derived MP allows rapid and dynamic estimation of mechanical power without any intervention at the bedside.