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

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.

journal_name

Crit Care Med

journal_title

Critical care medicine

authors

Valenza F,Guglielmi M,Maffioletti M,Tedesco C,Maccagni P,Fossali T,Aletti G,Porro GA,Irace M,Carlesso E,Carboni N,Lazzerini M,Gattinoni L

doi

10.1097/01.ccm.0000150660.45376.7c

subject

Has Abstract

pub_date

2005-02-01 00:00:00

pages

361-7

issue

eissn

0090-3493

issn

1530-0293

pii

00003246-200502000-00012

journal_volume

pub_type

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