The cardiovascular effects of acute hypoxemia as a diagnostic aid.

Acute hypoxemia produces opposite effects on the pulmonary and systemic vascular resistance. To assess the influence of acute hypoxemia on cardiac murmurs, 36 patients with a single valvular or congenital heart lesion were studied. As expected from these hemodynamic effects, right-sided regurgitant type murmurs increased in intensity during acute hypoxemia, while stenotic type murmurs were reduced. In contrast, left-sided murmurs remained constant or changed in opposite direction to their equivalent type from the right side. Additionally, acute hypoxemia produced a marked reduction of the murmurs due to left-to-right shunts and allowed an adequate differentiation of the murmurs due to ventricular septal defect from those due to mitral incompetence.