Changes in pulmonary hemodynamics during normoxia and hypoxia in awake rats treated with intratracheal bleomycin.

Pulmonary hemodynamics of bleomycin-induced interstitial fibrosis model (group-BLM, n = 10) and saline-treated control (group-C, n = 12) were studied in awake rats. Four weeks before hemodynamic study, bleomycin sulfate and normal saline was intratracheally instilled to the group-BLM and the group-C, respectively. Pulmonary artery and abdominal aortic catheters were indwelled two days before the hemodynamic study. In room air, mean pulmonary artery pressure (Ppa) was significantly higher and systemic artery pressure was significantly lower in group-BLM than in group-C; Ppa = 21 +/- 1 cmH2O (mean +/- S.E.) for group-C and 38 +/- 4 cmH2O for group-BLM. Cardiac output did not differ among the groups. Mean pulmonary vascular resistance (PVR) of group-BLM was double that of group-C. Right ventricle was hypertrophic in group-BLM. When exposed to 10% O2, PVR of group-C significantly rose, whereas PVR of group-BLM showed very little increase, showing attenuation of the hypoxic pulmonary vasoconstriction (HPV). Magnitude of the HPV was inversely related to Ppa during air breathing. We conclude that notable pulmonary hypertension and right ventricular hypertrophy occur, and HPV is blunted four weeks after bleomycin instillation, at the most severe period of this lung fibrosis model. We speculate that the high intravascular pressure partly contributed to the blunted HPV in bleomycin-treated group.