Effect of hyperoxia on contraction‐induced forearm blood flow dynamics in young healthy adults (1106.13)

Abstract

Hyperoxia can cause substantial reductions in peripheral and coronary blood flow at rest and during exercise. We tested the hypothesis that hyperoxia may increase the time for forearm blood flow (FBF) to reach steady state (SS) levels during exercise. Young (n=11; 28±2yr) healthy adults performed rhythmic forearm contractions at 10% of their maximum voluntary contraction for 5 minutes. Each duty cycle consisted of 1 second contraction and 2 second relaxation. Brachial artery diameters and velocities were measured using Doppler Ultrasound and forearm blood flow (ml/min) was calculated from the mean velocity and diameter. The dynamics of FBF at the onset of exercise were assessed by calculating the slope of the FBF response for every duty cycle between baseline and steady state, and the number of duty cycles to reach steady state. The slope of the line plotted from baseline FBF to SS, had a significantly attenuated slope under hyperoxia (5.4±1.1 ml/min/cycle) as compared to normoxia (10.6±2.6 ml/min/cycle). In addition, the number of duty cycles performed under hyperoxia (33±4 cycles) was significantly higher as compared to normoxia (25±4 cycles) (P<0.02). Our data suggest that hyperoxia attenuates the contraction‐induced FBF from baseline to SS as compared to normoxia.