Hyperoxia and coronary vessels

Q: Hyperoxia causes? (select one)

A) Coronary vasoconctriction

B) Coronary vasosilatation

Answer: A

Although it is true that oxygen is an essential requirement during coronary angina, "too much oxygen" (hyperoxia) is deleterious to coronary vessels. It induces coronary vasoconstriction. In animal models, it has shown to cause microscopic foci of myocardial necrosis. Other cardiac effects of hyperoxia are reduced stroke volume, decreased cardiac output, relative bradycardia, and increase systemic vascular resistance (SVR).

Clinically this can be significant in patients who require more than 60% of oxygen on ventilator for a prolonged period.

#pulmonary

#cardiology

References:

1. Ganz W, Donoso R, Marcus H, Swan HJ. Coronary hemodynamics and myocardial oxygen metabolism during oxygen breathing in patients with and without coronary artery disease. Circulation 1972; 45:763.

2. Büsing CM, Kreinsen U, Bühler F, Bleyl U. Light and electron microscopic examinations of experimentally produced heart muscle necroses following normobaric hyperoxia. Virchows Arch A Pathol Anat Histol 1975; 366:137.

3. Lodato RF. Decreased O2 consumption and cardiac output during normobaric hyperoxia in conscious dogs. J Appl Physiol (1985) 1989; 67:1551.