PULMONARY HYPERTENSION WITH SPECIAL REFERENCE TO THE VASOCONSTRICTIVE FACTOR*

The normal pulmonary blood pressure in a series of 60 normal controls studied at the Institute of Cardiology and at the Brompton hospital was 16/7 mm. Hg with reference to the sternal angle, the mean being 11 mm. and the range 8/2-28/14 mm. The mean cardiac output was 8 litres a minute, and the common range 5 5 to 10-5 litres a minute. The left atrial pressure averaged 2 to 3 mm. Hg. The pulmonary vascular resistance, which in simple units is the pulmonary artery pressure minus the left atrial pressure in mm. Hg divided by the pulmonary blood flow in litres a minute, was therefore about 1 unit or 80 dynes sec./cm.-5. Definition of Pulmonary Hypertension. Pulmonary hypertension literally implies a pulmonary blood pressure above 30/15 mm. which is the upper limit of the normal range. In practice serious pulmonary hypertension usually means a pressure at or around systemic level, but rarely in excess of 150 mm.