Fig. 3
From: Lung anatomy, energy load, and ventilator-induced lung injury
Energy calculation. Three examples of energy calculation in the following: a a pig ventilated with PEEP 0 cmH2O, b a pig ventilated with low PEEP (8 cmH2O), and c a pig ventilated at high PEEP (20 cmH2O). The energy load is composed of a static (when PEEP is higher than 0 cmH2O) and a dynamic contribution: global energy load = static energy load + dynamic energy load. Static energy load = [PEEP × PEEP volume/2] (light gray triangles). Dynamic energy load = (Peak pressure − PEEP) × TV/2 + (PEEP × TV) = [(PEEP + Peak pressure) × tidal volume / 2] (dark gray triangles (panel a) or trapezoids (panels b and c)). The dark gray trapezoids (panel b, c) are composed of a triangle (black dotted area), and a rectangle. The triangle represents the term (Peak pressure − PEEP) × TV/2, due to cyclic tidal breath; the rectangle represents the term (PEEP × TV) due to the ventilation (volume change) starting from a pressure level higher than zero (PEEP). Vertical dashed lines indicate PEEP and peak pressures; horizontal dashed lines PEEP volume and end-inspiratory volume (tidal volume is the difference between the two)