NEAR-INFRARED SPECTROPHOTOMETRY DETERMINED INTERCOSTAL MUSCLE O2 SATURATION DURING EXERCISE

Abstract

18 Near-infrared spectrophotometry determined deoxy- (Hb) and oxy-hemoglobin (HbO2) concentration changes of intercostal muscles were followed during cycling in eight healthy young men. At 59 W; 34±1% VO2max (mean±SEM), breathing frequency (RR) and ventilation (VE) were 27±2 brmin-1 and 31±4 lmin-1, respectively. HbO2 remained at the resting level whereas Hb decreased (−1.0±0.7 microMol; P < 0.05). As work rate increased to 176 W; 77±2% VO2max, only Hb deviated as it reached a level above rest (1.7±0.7 microMol; P < 0.05). During high intensity exercise (235 W; 93±2% VO2max), RR and VE were 42±2 bmin-1 and 108±4 lmin-1; heart rate reached 174±12 bmin-1 and cardiac output was 19±1 lmin-1. The concentration of total hemoglobin was not affected significantly by exercise, but Hb increased 4.6±1.3 microMol and HbO2 decreased −5.0±2.1 microMol (P < 0.05) although there was no significant change in O2 saturation of arterial blood. The results suggest that during intense exercise associated with an enhanced breathing frequency and volume, intercostal muscle blood flow is insufficient to maintain the tissue oxygenation.