Cardiorespiratory Responses to Hypoxia and Hypercapnia at Rest in Vocalists

Abstract

In order to clarify whether or not ventilatory and circulatory responses to hypoxia and hypercapnia at rest in male vocalists (n = 11) are identical to those of untrained subjects (n = 11), ventilatory responses to hypoxia (HVR) and hypercapnia (HCVR) were estimated as the slope of regression relating V˙I to SaO₂ (ΔV˙I/ΔSaO₂) or the slope factor (A) for the V˙I–PETO₂ curve, and as the slope of regression relating V˙I to PETCO₂ (ΔV˙I/ΔPETCO₂), respectively. The respiratory frequency (f), tidal volume (VT), heart rate (HR), and blood pressure (BP) responses to hypoxia and hypercapnia were also estimated as the slope of the line calculated by linear regression related to SaO₂ and PETCO₂. Mean values of ΔV˙I/ΔSaO₂ and A as an index of hypoxic ventilatory response were lower in the vocalist group (0.39 ± 0.25 l·min⁻¹·%⁻¹ and 76.8 ± 55.7 l·min⁻¹·torr⁻¹) than that in the control group (0.56 ± 0.46 l·min⁻¹·%⁻¹ and 101.6 ± 85.4 l·min⁻¹·torr⁻¹), and there was no statistically significant difference. The Δf/ΔSaO₂ was significantly (plt;0.05 ) lower in the vocalist group (−0.02 ± 0.39 breaths·min⁻¹·%⁻¹) than that in the control group (0.43 ± 0.65 breaths·min⁻¹·%⁻¹). In contrast, mean values of ΔV˙I/ΔPETCO₂ per body mass index were significantly (plt;0.05) lower in the vocalist group (0.05 ± 0.03 l·min⁻¹·torr⁻¹) than those in the control group (0.10 ± 0.06l·min⁻¹·torr⁻¹). There were also significant differences in ΔVT/ΔPETCO₂ and Δf/ΔPETCO₂ between the two groups (plt;0.05). However, no significant differences in HR and BP responses to hypoxia and hypercapnia between the two groups were observed. These results suggest that the magnitude of ventilatory response, but not HR and BP, to hypoxia and hypercapnia at rest in vocalists is reduced by chronic vocal training, including breath control and elongation of phonation for long periods.