Dynamic alveolar mechanics in four models of lung injury

Objective To determine whether pathological alterations in alveolar mechanics (i.e., the dynamic change in alveolar size and shape with ventilation) at a similar level of lung injury vary depending on the cause of injury.Design and setting Prospective controlled animal study in a university laboratory.Subjects 30 male Sprague-Dawley rats (300–550 g).Interventions Rats were separated into one of four lung injury models or control (n=6): (a) 2% Tween-20 (Tween, n=6), (b) oleic acid (OA, n=6), (c) ventilator-induced lung injury (VILI, PIP 40/ZEEP, n=6), (d) endotoxin (LPS, n=6). Alveolar mechanics were assessed at baseline and after injury (PaO₂/FIO₂ <300 mmHg) by in vivo microscopy.Measurements Alveolar instability (proportional change in alveolar size during ventilation) was used as a measurement of alveolar mechanics.Results Alveoli were unstable in Tween, OA, and VILI as hypoxemia developed (baseline vs. injury: Tween, 7±2% vs. 67±5%; OA: 3±2% vs. 82±9%; VILI, 4±2% vs. 72±5%). Hypoxemia after LPS was not associated with significant alveolar instability (baseline vs. injury: LPS, 3±2 vs. 8±5%).Conclusions These data demonstrate that multiple pathological changes occur in dynamic alveolar mechanics. The nature of these changes depends upon the mechanism of lung injury.Electronic Supplementary Material Electronic supplementary material to this paper can be obtained by using the Springer Link server located at .