The risk of
lung injury due to alveolar overdistension during
mechanical ventilation has been clearly delineated in healthy animals with intact lungs. In contrast, the effect of high-volume ventilation (HV) on previously injured lungs is less well documented: whether HV would simply add its own deleterious effects or act synergistically with previous injury has not been addressed. We compared the effect of 7 ml/kg
body weight tidal volume
mechanical ventilation for 2 min with that of 25 (HV25), 33(HV33), and 45(HV45) ml/kg
body weight HV in anesthetized rats previously exposed or not exposed to
alpha-naphthylthiourea (
ANTU).
ANTU alone produced moderate permeability
edema with significant increases in extravascular lung water (Qwl), dry lung weight (DLW), and
albumin distribution space in lungs (ASp). HV alone resulted in a permeability
edema in which severity was dependent on the magnitude of the tidal volume. The effects of HV25 and HV33 and those of
ANTU were only additive, as indicated by the absence of any significant two-factor (
ANTU-HV) interaction by analysis of variance (ANOVA). In contrast, HV45 after
ANTU produced significantly greater increases in Qwl, DLW, and ASp than expected from the sum of the effects of either insult alone. Two-way ANOVA disclosed two-factor interactions with p values < 0.001, < 0.02, and < 0.01 for Qwl, DLW, and ASp, respectively, indicating synergistic adverse effects on
pulmonary edema.(ABSTRACT TRUNCATED AT 250 WORDS)