The transient ventilatory response to carbon dioxide at rest and in exercise in man
1989; Elsevier BV; Volume: 77; Issue: 2 Linguagem: Inglês
10.1016/0034-5687(89)90009-1
ISSN1872-7611
AutoresM. S. Jacobi, C.P. Patil, K.B. Saunders,
Tópico(s)Respiratory Support and Mechanisms
ResumoA new technique has been developed to measure the transient response to inhaled CO2 using 30 sec pulses at constant inflow. Multiple experiments are ensemble-averaged in order to define the resulting small signals. We measured the peak changes in ventilation (ΔV′) and in PCO2 (ΔPCO2), taking the ratio (ΔV′/ΔPCO2) as an index of response. Six healthy volunteers experiments at rest, 50 W and 100 W exercise. Three runs, each containing three pulses, were performed at each workload and subsequently averaged. Analysis of variance showed no significant difference between successive pulses or among subjects. ΔV′ did not differ significantly with workload, but ΔPCO2 was progressively smaller as workload increased, and hence the response, ΔV′/ΔPCO2, greater. The delay between the rise in PCO2 and the rise in ventilation was also progressively shorter as workload increased, being 16–18 sec at rest, 7–13 sec at 50 W, and 3–6 sec at 100 W. Our results suggest that there is increased sensitivity to CO2 in exercise, which may be due to progressive activation of the peripheral chemoreceptors as work load increases. The delay at rest is too long for the peripheral chemoreceptor. Therefore, with these small stimuli, the central chemoreceptor must account for the CO2 response at rest.
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