Prone position delays the progression of ventilator-induced lung injury in rats: Does lung strain distribution play a role?

Franco Valenza, Massimiliano Guglielmi, Micol Maffioletti, Cecilia Tedesco, Patrizia Maccagni, Tommaso Fossali, Gabriele Aletti, Giuliana Anna Porro, Manuela Irace, Eleonora Carlesso, Nadia Carboni, Marco Lazzerini, Luciano Gattinoni

Research output: Contribution to journalArticlepeer-review

Abstract

Objective: To investigate if prone position delays the progression of experimental ventilator-induced lung injury, possibly due to a more homogeneous distribution of strain within lung parenchyma. Design: Prospective, randomized, controlled trial. Setting: Animal laboratory of a university hospital. Subjects: Thirty-five Sprague Dawley male rats (weight 257 ± 45 g). Interventions: Mechanical ventilation in either supine or prone position and computed tomography scan analysis. Measurements: Animals were ventilated in supine (n = 15) or prone (n = 15) position until a similar ventilator-induced lung injury was reached. To do so, experiments were interrupted when respiratory system elastance was 150% of baseline. Ventilator-induced lung injury was assessed as lung wet-to-dry ratio and histology. Time to reach lung injury was considered as a main outcome measure. In five additional animals, computed tomography scans (GE Light Speed QX/I, thickness 1.25 mm, interval 0.6 mm, 100 MA, 100 Kv) were randomly taken at end-expiration and end-inspiration in both positions, and quantitative analysis was performed. Data are shown as mean ± SD. Measurements and Main Results: Similar ventilator-induced lung injury was reached (respiratory system elastance, wet-to-dry ratio, and histology). The time taken to achieve the target ventilator-induced lung injury was longer with prone position (73 ± 37 mins vs. 112 ± 42, supine vs. prone, p = .011). Computed tomography scan analysis performed before lung injury revealed that at end-expiration, the lung was wider in prone position (p = .004) and somewhat shorter (p = .09), despite similar lung volumes (p = .455). Lung density along the vertical axis increased significantly only in supine position (p = .002). Lung strain was greater in supine as opposed to prone position (width strain, 7.8 ± 1.8% vs. 5.6 ±0.9, supine vs. prone, p = .029). Conclusions: Prone position delays the progression of ventilator-induced lung injury. Computed tomography scan analysis suggests that a more homogeneous distribution of strain may be implicated in the protective role of prone position against ventilator-induced lung injury.

Original languageEnglish
Pages (from-to)361-367
Number of pages7
JournalCritical Care Medicine
Volume33
Issue number2
DOIs
Publication statusPublished - Feb 2005

Keywords

  • Acute
  • Animal experimentation
  • Lung injury
  • Prone position
  • Tomography, spiral computed
  • Ventilation

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine

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