Mechanisms of acute lung injury. What have we learned from experimental animal models?

Studies have shown that there are at least two broad categories of acute lung injuries: those that require polymorphonuclear leukocytes, and those that do not. Knowledge from animal experiments is very incomplete, and the relevance of animal models to human disease is unknown. Specific therapy appears to be a distant goal, because there is no single underlying mechanism of lung injury, and because there is no way to precisely identify what injured the lung or to make a clinical diagnosis early enough in lung injury. Many possibilities for therapy are based on interfering with inflammation, and may therefore increase susceptibility to infection. Considerable progress is being made, but there is much left to learn.