ABSTRACT
OVERVIEW The pulmonary circulation is normally a low pressure, low resistance, high capacitance system. Normal pulmonary arterial (PA) pressures in dogs are about 25 mm Hg systolic, 8 mm Hg diastolic, and 12-15 mm Hg mean. These low PA pressures minimize RV workload and maintain optimal RV myocardial blood flow1, 2. Increases in pulmonary blood flow are usually accommodated with minimal increase in PA pressure because of the highly distensible thin-walled pulmonary vasculature, recruitment of underperfused vessels, and a large pulmonary capillary surface area1, 3. In dogs with normal lungs, up to 60% of the pulmonary vascular bed can be lost before pulmonary hypertension develops1.
