Revisiting the role of oxygen therapy in cardiac patients

Abstract

Over the past century, multiple studies lacking the precision of today's advanced technology provided conflicting data on the effects of oxygen therapy in normoxic cardiac patients. More importantly, no randomized, blinded, controlled studies have shown a benefit of such treatment. Yet the use of supplemental oxygen is widespread in cardiac patients. In these conditions, inadvertent hyperoxia commonly occurs because of concerns to ensure sufficient oxygenation and because hyperoxia is not perceived to be detrimental. In recent years, there has been mounting evidence demonstrating the potential adverse effects of hyperoxia on the cardiovascular system. In this report, we review data examining the effects of supplemental oxygen in normoxic patients with acute presentations of coronary artery disease. It is also the aim of this report to emphasize the point that oxygen therapy might have major adverse physiologic effects that must be considered when it is employed.

Figure 1

Pulsed Doppler recording of left anterior descending coronary artery in healthy subjects and cardiac transplant patients. Blood flow velocity is significantly decreased in both groups during hyperoxia.

Figure 2

Individual and mean responses of coronary blood velocity and coronary vascular resistance in normal subjects (gray arrows) and transplant patient (open arrows). Bold arrows represent mean data. The pressure-rate product is an index of myocardial O2 consumption.

Figure 3

Individual data for coronary blood flow (CBF) and coronary vascular resistance (CVR) in subjects during sequential room air and 100% oxygen breathing. Reproduced with permission from McNulty and et al. (Am J Physiol Heart Circ Physiol 288: H1057–H1062, 2005).