Ventilator-related causes of lung injury: the mechanical power

• Published in: Intensive care medicine Vol. 42; no. 10; pp. 1567 - 1575
• Main Authors: Gattinoni, L., Tonetti, T., Cressoni, M., Cadringher, P., Herrmann, P., Moerer, O., Protti, A., Gotti, M., Chiurazzi, C., Carlesso, E., Chiumello, D., Quintel, M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.10.2016; Springer; Springer Nature B.V
• Subjects: Adult; Aged; Airway Resistance - physiology; Anesthesiology; Case-Control Studies; Critical Care Medicine; Edema; Emergency Medicine; Energy; Female; Humans; Intensive; Intensive care; Logistic Models; Lung - physiopathology; Lung diseases; Male; Medicine; Medicine & Public Health; Middle Aged; Original; Pain Medicine; Pediatrics; Pneumology/Respiratory System; Positive-Pressure Respiration - methods; Respiratory Distress Syndrome - therapy; Respiratory Mechanics - physiology; Respiratory system; Tidal Volume - physiology; Ventilator-Induced Lung Injury - etiology; Ventilators; Ventilators, Mechanical - adverse effects; Italy; United Kingdom; VILI; Respiratory mechanics; Mechanical ventilation; ARDS
• ISSN: 0342-4642; 1432-1238; 1432-1238
• DOI: 10.1007/s00134-016-4505-2

Purpose We hypothesized that the ventilator-related causes of lung injury may be unified in a single variable: the mechanical power. We assessed whether the mechanical power measured by the pressure–volume loops can be computed from its components: tidal volume (TV)/driving pressure (∆ P aw ), flow, positive end-expiratory pressure (PEEP), and respiratory rate (RR). If so, the relative contributions of each variable to the mechanical power can be estimated. Methods We computed the mechanical power by multiplying each component of the equation of motion by the variation of volume and RR: Power rs = RR · Δ V 2 · 1 2 · EL rs + RR · 1 + I : E 60 · I : E · R aw + Δ V · PEEP , where ∆ V is the tidal volume, EL rs is the elastance of the respiratory system, I : E is the inspiratory-to-expiratory time ratio, and R aw is the airway resistance. In 30 patients with normal lungs and in 50 ARDS patients, mechanical power was computed via the power equation and measured from the dynamic pressure–volume curve at 5 and 15 cmH 2 O PEEP and 6, 8, 10, and 12 ml/kg TV. We then computed the effects of the individual component variables on the mechanical power. Results Computed and measured mechanical powers were similar at 5 and 15 cmH 2 O PEEP both in normal subjects and in ARDS patients (slopes = 0.96, 1.06, 1.01, 1.12 respectively, R 2  > 0.96 and p  < 0.0001 for all). The mechanical power increases exponentially with TV, ∆ P aw , and flow (exponent = 2) as well as with RR (exponent = 1.4) and linearly with PEEP. Conclusions The mechanical power equation may help estimate the contribution of the different ventilator-related causes of lung injury and of their variations. The equation can be easily implemented in every ventilator’s software.