Fig. 1
From: Which component of mechanical power is most important in causing VILI?
a Left Panel: Elastic and flow resistive components of the total energy per tidal cycle during passive constant flow. b Right Panel: An arbitrarily assumed threshold for damaging pressure divides total tidal energy into subcomponent blocks below and above the boundary that separates potentially non-injurious (blocks G, D, and E) from injurious contributors (blocks F, A, B, and C), respectively. Simple algebraic estimates for each can be developed from clinical data using pre-specified parameters of mechanics or empirically observed measurements at the bedside. Example: total power = f × [A + B + C + D + E + F + G] = V’E × (RV’ + VT/2c + PEEP) or alternatively: (V’E/2) × (2 Ppeak − Pplat + PEEP). Total Dynamic Excessive Power = f × [A + B + C] = V’E × {1 + [(PEEP − PT) × c]/VT} × ½ [(VT/c) + PEEP + PT] or alternatively: V’E × [(Pplat − PT)/(Pplat − PEEP)] × [(Pplat + PT)/2)]. Abbreviations: R = Resistance; c = Compliance