Lung stress and strain during mechanical ventilation: Any difference between statics and dynamics?

Alessandro Protti, Davide T. Andreis, Massimo Monti, Alessandro Santini, Cristina C. Sparacino, Thomas Langer, Emiliano Votta, Stefano Gatti, Luciano Lombardi, Orazio Leopardi, Serge Masson, Massimo Cressoni, Luciano Gattinoni

Research output: Contribution to journalArticle

Abstract

Objective: Tidal volume (VT) and volume of gas caused by positive end-expiratory pressure (VPEEP) generate dynamic and static lung strains, respectively. Our aim was to clarify whether different combinations of dynamic and static strains, resulting in the same large global strain, constantly produce lung edema. Design: Laboratory investigation. Setting: Animal unit. Subjects: Twenty-eight healthy pigs. Interventions: After lung computed tomography, 20 animals were ventilated for 54 hours at a global strain of 2.5, either entirely dynamic (VT 100% and VPEEP 0%), partly dynamic and partly static (VT 75-50% and VPEEP 25-50%), or mainly static (VT 25% and VPEEP 75%) and then killed. In eight other pigs (VT 25% and VPEEP 75%), VPEEP was abruptly zeroed after 36-54 hours and ventilation continued for 3 hours. Measurements and Main Results: Edema was diagnosed when final lung weight (balance) exceeded the initial weight (computed tomography). Mortality, lung mechanics, gas exchange, pulmonary histology, and inflammation were evaluated. All animals ventilated with entirely dynamic strain (VT 825 ± 424 mL) developed pulmonary edema (lung weight from 334 ± 38 to 658 ± 99 g, p <0.01), whereas none of those ventilated with mainly static strain (VT 237 ± 21 mL and VPEEP 906 ± 114 mL, corresponding to 19 ± 1 cm H2O of positive end-expiratory pressure) did (from 314 ± 55 to 277 ± 46 g, p = 0.65). Animals ventilated with intermediate combinations finally had normal or largely increased lung weight. Smaller dynamic and larger static strains lowered mortality (p <0.01), derangement of lung mechanics (p <0.01), and arterial oxygenation (p <0.01), histological injury score (p = 0.03), and bronchoalveolar interleukin-6 concentration (p <0.01). Removal of positive end-expiratory pressure did not result in abrupt increase in lung weight (from 336 ± 36 to 351 ± 77 g, p = 0.51). Conclusions: Lung edema forms (possibly as an all-or-none response) depending not only on global strain but also on its components. Large static are less harmful than large dynamic strains, but not because the former merely counteracts fluid extravasation.

Original languageEnglish
Pages (from-to)1046-1055
Number of pages10
JournalCritical Care Medicine
Volume41
Issue number4
DOIs
Publication statusPublished - Apr 2013

Keywords

  • healthy lung
  • lung strain
  • lung stress
  • mechanical ventilation
  • positive end-expiratory pressure
  • transpulmonary pressure
  • ventilator-induced lung injury

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine

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    Protti, A., Andreis, D. T., Monti, M., Santini, A., Sparacino, C. C., Langer, T., Votta, E., Gatti, S., Lombardi, L., Leopardi, O., Masson, S., Cressoni, M., & Gattinoni, L. (2013). Lung stress and strain during mechanical ventilation: Any difference between statics and dynamics? Critical Care Medicine, 41(4), 1046-1055. https://doi.org/10.1097/CCM.0b013e31827417a6