The relationship between the arterial level of angiotensin-converting enzymes and arterial gas tension in bronchial asthma

To study the mechanism which causes a lowered serum level of angiotensin-converting enzyme (ACE) in asthma patients, the changes in serum ACE in arterial blood gas tension was measured. Serum ACE was also determined in patients with chronic obstructive lung disease (COLD) and fibrosing lung disease (FLD). A reduced level of serum ACE was found in some patients with COLD, similar to that in patients with asthma. A significant relationship existed between the lowered serum ACE level and the degree of arterial hypoxia, especially in asthmatic patients and some patients with COLD. The significance of lowered serum ACE is discussed in relation to the pathogenesis and the mechanism of hypoxemia in patients with asthma, COLD and FLD.