Attenuated Ventilatory Responses to Hypercapnia and Hypoxia in Assisted Breath-hold Divers (Funado)

抄録

The steady-state ventilatory responses to hypercapnia and hypoxia in 7 assisted breath-hold divers (Funado) were compared with those in 7 normal sedentary controls.
Ventilatory response to hypercapnia was measured from the slope of the hyperoxic VN-PET_CO2 line, where VN was normalized minute ventilation using the allometric coefficient and PET_CO2 end-tidal P_CO2. The slope of this line in the Funado (1.48±0.54 liters·min^-1·Torr^-1) was significantly less than in the control (2.70±1.08 liters·min^-1·Torr^-1)(p<0.025). On the other hand, hypoxic sensitivity estimated by hyperbolic and exponential mathematical equations was not found to be significantly different between the two groups, although estimated increments in ventilation using the hyperbolic equation exhibited significantly lower response in the Funado than in the control only when PET_O2 decreased lower than 50 Torr (p<0.05).
These findings in the Funado were different from our previous observations obtained in unassisted breath-hold divers (Kachido), in whom no obvious attenuations in CO₂sensitivity were seen. This difference was assumed to be derived from more hypercapnic and hypoxic conditions produced in the Funado than in the Kachido during diving activities.