Effects of dynamic ventilatory factors on ventilator-induced lung injury in acute respiratory distress syndrome dogs.

Background: Mechanical ventilation is a double-edged sword to acute respiratory distress syndrome (ARDS) including lung injury, and systemic inflammatory response high tidal volumes are thought to increase mortality. The objective of this study is to evaluate the effects of dynamic ventilatory factors on ventilator induced lung injury in a dog model of ARDS induced by hydrochloric acid instillation under volume controlled ventilation and to investigate the relationship between the dynamic factors and ventilator-induced lung injuries (VILI) and to explore its potential mechanisms.

Methods: Thirty-six healthy dogs were randomly divided into a control group and an experimental group. Subjects in the experimental group were then further divided into four groups by different inspiratory stages of flow. Two mL of alveolar fluid was aspirated for detection of IL-8 and TNF-α. Lung tissue specimens were also extracted for total RNA, IL-8 by western blot and observed under an electronic microscope.

Results: IL-8 protein expression was significantly higher in group B than in groups A and D. Although the IL-8 protein expression was decreased in group C compared with group B, the difference was not statistically significant. The TNF-α ray degree of group B was significantly higher than that in the other groups (P<0.01), especially in group C (P>0.05). The alveolar volume of subjects in group B was significantly smaller, and cavity infiltration and cell autolysis were marked with a significant thicker alveolar septa, disorder of interval structures, and blurring of collagenous and elastic fiber structures. A large number of necrotic debris tissue was observed in group B.

Conclusion: Mechanical ventilation with a large tidal volume, a high inspiratory flow and a high ventilation frequency can cause significant damage to lung tissue structure. It can significantly increase the expression of TNF-α and IL-8 as well as their mRNA expression. Furthermore, the results of our study showed that small tidal ventilation significantly reduces the release of pro-inflammatory media. This finding suggests that greater deterioration in lung injury during ARDS is associated with high inspiratory flow and high ventilation rate.