Relationship of pulmonary arterial pressure and airflow obstruction to emphysema

Guinea pigs were exposed to cigarette smoke for 6 mo, after which lung and cardiac function and lung morphology were examined. The smoke-exposed animals were divided into two groups on the basis of final pulmonary arterial pressure. We found that the smoke-exposed animals with increased pulmonary arterial pressure had a moderate degree of airflow obstruction compared with the normotensive smoke group, which showed only mild airflow obstruction, and with the control group. Both smoke groups had similar degrees of emphysema. Although both smoke groups had an increased percentage of muscularized small arterioles, only the group with increased pulmonary arterial pressure had an altered flow-pressure response to dobutamine. We conclude that although cigarette smoke appears to induce changes in the vascular structure and to produce emphysematous lung destruction, the increased pulmonary arterial pressure in guinea pigs chronically exposed to smoke is not directly related to either of these findings. Instead, it appears that there is a dynamic alteration of both the airways, producing airflow obstruction, and the vasculature, producing increased pulmonary arterial pressure.