Metabolic indices of pulmonary damage. Changes in angiotensin converting enzyme and alpha 1 anti-trypsin activity after cardiopulmonary bypass.

The activity of angiotensin-converting enzyme was measured in patients undergoing cardiopulmonary bypass and in a control group requiring thoracotomy for pulmonary surgery. The activity of the enzyme was higher in patients with cardiac disease, fell during operations involving cardiopulmonary bypass, but did not change during thoracotomy for pulmonary surgery. Possible reasons for these differences are discussed. The activity of another enzyme, alpha 1 anti-trypsin, did not change during cardiopulmonary bypass and no arteriovenous difference could be detected during or after operation.