Home | User not signed in

- Online First (82)
- Current Issue
- Past Issues
- Supplements
- Top 10 Articles
- Most Cited Article
- Focus Editorials
- Letters to the Editor

- About Intensive Care Medicine
- Instructions to Authors
- Register for TOC Alert
- Members' Information & Subscriptions
- Editorial Board
- Submit a Manuscript
- Contact Us

**L. Gattinoni| T. Tonetti| M. Cressoni| P. Cadringher| P. Herrmann| O. Moerer| A. Protti| M. Gotti| C. Chiurazzi| E. Carlesso| D. Chiumello| M. Quintel**

Original**
Volume 42,
Issue
10
/
October ,
2016**

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.

We computed the mechanical power by multiplying each component of the equation of motion by the variation of volume and RR: $${\text{Power}}_{\text{rs}} = {\text{RR}} \cdot \left\{ {\Delta V^{2} \cdot \left[ {\frac{1}{2} \cdot {\text{EL}}_{\text{rs}} + {\text{RR}} \cdot \frac{{\left( {1 + I:E} \right)}}{60 \cdot I:E} \cdot R_{\text{aw}} } \right] + \Delta V \cdot {\text{PEEP}}} \right\},$$Powerrs=RR·ΔV2·12·ELrs+RR·1+I:E60·I:E·Raw+ΔV·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.

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.

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.

- Kumar A et al (1973) Pulmonary barotrauma during mechanical ventilation. Crit Care Med 1(4):181–186

- Dreyfuss D et al (1988) High inflation pressure pulmonary edema. Respective effects of high airway pressure, high tidal volume, and positive end-expiratory pressure. Am Rev Respir Dis 137(5):1159–1164

- Protti A et al. (2016) Role of strain rate in the pathogenesis of ventilator-induced lung edema. Crit Care Med 44(9):e838–e845. doi:10.1097/CCM.0000000000001718

- Hotchkiss JR Jr et al (2000) Effects of decreased respiratory frequency on ventilator-induced lung injury. Am J Respir Crit Care Med 161(2 Pt 1):463–468

- Cressoni M et al (2016) Mechanical power and development of ventilator-induced lung injury. Anesthesiology 124(5):1100–1108. doi:10.1097/ALN.0000000000001056

- Gattinoni L et al (1987) Pressure-volume curve of total respiratory system in acute respiratory failure. Computed tomographic scan study. Am Rev Respir Dis 136(3):730–736

- Cressoni M et al (2014) Lung inhomogeneity in patients with acute respiratory distress syndrome. Am J Respir Crit Care Med 189(2):149–158

- Gattinoni L et al (1995) Effects of positive end-expiratory pressure on regional distribution of tidal volume and recruitment in adult respiratory distress syndrome. Am J Respir Crit Care Med 151(6):1807–1814

- Tremblay L et al (1997) Injurious ventilatory strategies increase cytokines and c-fos m-RNA expression in an isolated rat lung model. J Clin Investig 99(5):944–952

- Otis AB, Fenn WO, Rahn H (1950) Mechanics of breathing in man. J Appl Physiol 2(11):592–607

- Marini JJ, Crooke PS 3rd (1993) A general mathematical model for respiratory dynamics relevant to the clinical setting. Am Rev Respir Dis 147(1):14–24

- Chiumello D et al (2008) Lung stress and strain during mechanical ventilation for acute respiratory distress syndrome. Am J Respir Crit Care Med 178(4):346–355

- Valenza F et al (2003) Positive end-expiratory pressure delays the progression of lung injury during ventilator strategies involving high airway pressure and lung overdistention. Crit Care Med 31(7):1993–1998

- Brunner JX, Wysocki M (2009) Is there an optimal breath pattern to minimize stress and strain during mechanical ventilation? Intensive Care Med 35(8):1479–1483

- Caironi P et al (2011) Time to generate ventilator-induced lung injury among mammals with healthy lungs: a unifying hypothesis. Intensive Care Med 37(12):1913–1920

- Rodarte JR, Rehder K (1986) Dynamics of respiration. In: Macklem PT, Mead J (eds) Handbook of Physiology. Williams & Wilkins, Baltimore, pp 131–144
- Pelosi P et al (1995) Alterations of lung and chest wall mechanics in patients with acute lung injury: effects of positive end-expiratory pressure. Am J Respir Crit Care Med 152(2):531–537

- Guerin C, Fournier G, Milic-Emili J (2001) Effects of PEEP on inspiratory resistance in mechanically ventilated COPD patients. Eur Respir J 18(3):491–498

- Protti A et al (2015) Lung anatomy, energy load, and ventilator-induced lung injury. Intensive Care Med Exp 3(1):34

- Gattinoni L, Pesenti A (2005) The concept of “baby lung”. Intensive Care Med 31(6):776–784

- Bachofen H, Hildebrandt J (1971) Area analysis of pressure-volume hysteresis in mammalian lungs. J Appl Physiol 30(4):493–497

- Fredberg JJ, Stamenovic D (1989) On the imperfect elasticity of lung tissue. J Appl Physiol 67(6):2408–2419

- Gattinoni L et al (2016) The “baby lung” became an adult. Intensive Care Med 42(5):663–673

- Amato MBP et al (2000) Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. The acute respiratory distress syndrome network. N Engl J Med 342(18):301–308