Ventilatory response to CO2 after brief stimulations of the peripheral chemoreceptors in man

Whether or not stimulation of the peripheral chemoreceptors by hypercapnic-hypoxic exposure results in a long-lasting increase in ventilatory activities was studied using the steady state CO2 response test on 12 human subjects. The degree of hypercapnic hypoxia was end-tidal PCO2 (PETCO2) 42.1 +/- 3.0 and PO2 (PETO2) 39.8 +/- 4.7 mmHg, lasting for 5 min. Minute ventilation values at PETCO2 45 mmHg (V45) and PETCO2 at minute volume 15 liter . min-1 (P15) were calculated from the respective CO2 response curves. The differences in V45 and P15 between the control and the 30 min test group were found to be significant (p less than 0.05). These results suggested the left- and upward-shift of the CO2 response curve of the 30 min test group. On the other hand, in 5 of the 12 subjects, three successive CO2 response tests conducted at 0, 30, and 90 min without hypercapnic-hypoxic exposure showed fairly reproducible results, and no statistically significant differences were found between any of the above trials with the parameters S, B, V45, and P15. These results indicated that the CO2 response curve obtained by using the steady state method can be effected for at least 30 min even if the stimulation of the peripheral chemoreceptors is only for brief periods.