Cardiorespiratory Responses to Hypoxia and Hypercapnia at Rest in Vocalists
The Japanese Journal of Physiology
It has hitherto been reported that hypoxic and hypercapnic ventilatory responses at rest are lower in the well-trained athletes, long-distance swimmers, and elite synchronized swimmers as compared to untrained subjects    . Furthermore, there are several studies concerning blunted ventilatory responses to hypoxia and hypercapnia in free divers (e.g., Igarashi  showed reduced hypercapnic ventilatory responses in the ama, people who harvest shellfish and seaweed only during harvest
... sons using no special breathing apparatus). It has been confirmed by a few authors    that divers, compared to nondivers, had a blunted chemosensitivity to hypercapnia. Masuda et al. [8, 9] also indicated decreased ventilatory response to hypercapnia in the Funado, people who dive to depths of 10-20 m, and to hypoxia in the Kachido, people who dive at shallow depths of 5-10 m, respectively. On the other hand, a unique group of musicians, formal classical singers, or so-called professional vocalists, perform vigorous respiratory exercise while extending their breath and may need to be endowed with special characteristics in their control of ventilation, which allow them to perform at an elite level of Abstract: In order to clarify whether or not ventilatory and circulatory responses to hypoxia and hypercapnia at rest in male vocalists (nϭ11) are identical to those of untrained subjects (nϭ11), ventilatory responses to hypoxia (HVR) and hypercapnia (HCVR) were estimated as the slope of regression relating VI to Sa O 2 (⌬VI/⌬Sa O 2 ) or the slope factor (A) for the VI-PET O 2 curve, and as the slope of regression relating VI to PET CO 2 (⌬VI/⌬PET CO 2 ), respectively. The respiratory frequency (f ), tidal volume (V T), 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 Sa O 2 and PET CO 2 . Mean values of ⌬VI/⌬Sa O 2 and A as an index of hypoxic ventilatory response were lower in the vocalist group (0.39Ϯ0.25 l · min Ϫ1 · % Ϫ1 and 76.8Ϯ55.7 l · min Ϫ1 · torr Ϫ1 ) than that in the control group (0.56Ϯ0.46 l · min Ϫ1 · % Ϫ1 and 101.6Ϯ 85.4 l · min Ϫ1 · torr Ϫ1 ), and there was no statisti-cally significant difference. The ⌬f/⌬Sa O 2 was significantly (pϽ0.05 ) lower in the vocalist group (Ϫ0.02Ϯ0.39 breaths · min Ϫ1 · % Ϫ1 ) than that in the control group (0.43Ϯ0.65 breaths · min Ϫ1 · % Ϫ1 ). In contrast, mean values of ⌬VI/⌬PET CO 2 per body mass index were significantly (pϽ0.05) lower in the vocalist group (0.05Ϯ0.03 l · min Ϫ1 · torr Ϫ1 ) than those in the control group (0.10Ϯ0.06l · min Ϫ1 · torr Ϫ1 ). There were also significant differences in ⌬V T/⌬PET CO 2 and ⌬f/⌬PET CO 2 between the two groups (pϽ0.05). 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.