Effects of increased respiratory rate on cortical oxygenated hemoglobin during low-intensity exercise

Abstract

This study aimed to examine whether the end-tidal partial pressure of CO₂ (PEtCO₂) affects the concentration of oxygenated hemoglobin (O₂Hb) measured by near-infrared spectroscopy (NIRS). Participants were examined under the conditions of normal and increased ventilation. We measured O₂Hb, mean blood pressure, skin blood flow, PEtCO₂, respiratory rate, and minute volume at 30 % of the maximum oxygen uptake during exercise. ΔO₂Hb and PEtCO₂ during exercise were lower in the increased ventilation than in the normal ventilation condition. Pearson's product-moment correlation analysis showed a significant positive correlation between ΔO₂Hb and ΔMAP, ΔSBF, and PEtCO₂. Correlation coefficients were 0.249 (p < 0.001) for ΔMAP, 0.343 (p < 0.001) for ΔSBF, and 0.315 (p < 0.001) for PEtCO₂. In conclusion, we identified increased ventilation during bicycle ergometer exercise as a significant factor associated with significantly low PEtCO₂ and ΔO₂Hb.

Keywords: Bicycle ergometer; Cortical oxygenated hemoglobin; End-tidal partial pressure CO(2); Increased ventilation.