Interaction between previous lung alterations and mechanical ventilation on pulmonary edema. Effect of previous toxic lung injury. Extravascular lung water (Qwl) after mechanical ventilation in normal rats (open circles) and in rats with mild lung injury produced by α-naphthylthiourea (ANTU) (closed circles). Tidal volume (V
) varied from 7 to 45 ml/kg body weight. The solid line represents the Qwl value expected for the aggravating effect of ANTU on edema caused by ventilation, assuming additivity. ANTU did not potentiate the effect of ventilation with V
up to 33 ml/kg body weight. In contrast, V
45 ml/kg body weight produced an increase in edema that greatly exceeded additivity, indicating synergy between the two insults. Used with permission. From Dreyfuss et al. .