EFFECTS OF OXYGEN ON FOREARM DILATOR CAPACITY

We have previously shown that supplemental oxygen reduces cardiac output and raises systemic vascular resistance in congestive heart failure (CHF) patients. In this study, we examine the effects of 100% oxygen on forearm vascular resistance after 10 minutes of forearm circulatory arrest. Forearm circulatory arrest is a potent vasodilator stimulus. Forearm flow(Q), (plethysmography; ml/min/100 ml) and R (blood pressure divided by Q)) are measured 5 seconds after releasing forearm circulatory arrest and then every 15 seconds for 3 minutes. Oxygen raised the minimum R and increased the rate of rise of R towards baseline. In a second study, we examine whether "peripheral abnormalities" as might be seen in CHF would enhance the oxygen effect. The high sympathetic tone of CHF was simulated by lower body negative pressure(LBNP,-30 mmHg); the edema of CHF by forearm congestion (90 mmHg arm cuff inflation 5 minutes before initiating forearm circulatory arrest. R is measured in a control state, with LBNP, with LBNP plus forearm congestion and when oxygen is added to LBNP plus forearm congestion. Data from each condition will be compared with each of the other conditions and with the data from the first study.