THE EQUILIBRIUM CO2 REBREATHING METHOD DOES NOT AFFECT RESTING OR EXERCISE BLOOD-PRESSURE

The equilibrium CO2 rebreathing technique has been widely used for the noninvasive determination of cardiac output. Recently, several invest igators have used this technique in conjunction with auscultatory bloo d pressure measurements to calculate total peripheral resistance. To e xamine the validity of this approach, we attempted to determine whethe r the CO2 rebreathing procedure has a significant effect on blood pres sure. The participants in the present study were 10 male subjects, 24 +/- 1 yr of age (mean +/- SE). Each subject performed two trials-one w ith CO2 rebreathing and one without. Both trials consisted of three st ages (rest, 25%, and 50% VO2peak), each stage lasting 15 min. During t he rebreathing trial, the CO2 rebreathing technique was administered a t 10 min into each stage. There were no statistically significant diff erences in the heart rate, systolic blood pressure, diastolic blood pr essure, and mean arterial blood pressure responses between the two tri als. These results indicate that the equilibrium CO2 rebreathing techn ique does not alter auscultatory blood pressures at rest and during ex ercise up to intensities of 50% VO2peak.