The pH oscillations in arterial blood during exercise; a potential signal for the ventilatory response in the dog

Abstract

SUMMARY1. The effect of electrically induced 'exercise' on the respiratory oscillation of arterial pH was studied in chloralose-anaesthetized dogs with spinal cord transaction at T8/9 (dermatome level T6/7).2. Respiratory oscillations of arterial pH (presumed to be due to oscillations of arterial Pco2) were sensed with a fast-responding electrode in one carotid artery.Breath-by-breath estimates of the maximum rate of change of pH of the downstroke of the pH oscillation (dpH/dtjmax) were obtained by differentiating the pH signal.3. Consistent with the findings of the previous paper (Cross et al. 1982), the ventilatory response to exercise could not be explained on the basis of sensitivity to C02; the A T4/APaco, was significantly greater for 'exercise' than for CO2 inhalation.4. On average, the amplitude of the pH oscillations decreased during 'exercise'.The change in the phase relationship (0) between respiratory and pH cycles, although significant from the second breath onwards, was not thought to be responsible for the increased ventilation V,; the direction of the change was opposite to that previously found to increase VI. 14 and dpH/dtjmax were also linearly related during the on-transient, although the same relationship did not hold true throughout 'exercise'.6. The dpH/dtjmax was related to CO2 production (1rco,) lending support to the prediction that the slope of the downstroke of the pH oscillation is a function of TCo2.7. It was concluded that the dpH/dtimax (dpCO2/dttmax) is a potential humoral signal in 'exercise' and could account totally for the shortening of te. Since there was a late rise in VI (due to an increase in tidal volume VT) in the absence of a change in dpH/dtjmax, it was considered unlikely that the dpH/dtjmax was the only humoral signal present during 'exercise'.

Communications

“…In all three subjects the peak of the TE oscillation generally appeared after the maximum values for VTE and VE but before their minimum values. These results are in complete agreement with the results from the step inputs of Gardner (1980 In an earlier communication to the Society, it was postulated that the maximum rate of change of the downstroke of the pH oscillation (dpH/dtlmax) is the missing link between CO2 production and ventilation during electrically-induced exercise in the dog (Cross, Guz, Katona, Maclean, Murphy, Semple & Stidwill, 1980). We have further examined the relationship between these variables during venous CO2 loading in the cat.…”

Development of Carotid Chemoreceptor Dynamic and Steady‐State Sensitivity to CO2 in the Newborn Lamb

“…Changes in Pa,COµ provide an important stimulus for the initiation of continuous breathing at birth (Woodrum, Parer, Wennberg & Hodson, 1972;Kuipers, Maertzdorf, de Jong, Hanson & Blanco, 1994). The amplitude of the oscillation in chemoreceptor discharge is determined by the Pa,COµ oscillations, and is influenced by metabolism (Cross et al 1982). This relationship between metabolism and ventilation, and the role of COµ in controlling ventilation, has important implications for the role of peripheral chemoreceptor function in the aetiology of sudden infant death syndrome (SIDS).…”

The role of spinal cord transmission in the ventilatory response to electrically induced exercise in the anaesthetized dog

“…Such crucial coupling of these two variables has been shown to be a feature of exercise in man, dog and cat (Wasserman et al 1980) and more recently has been extended to the sheep both in the resting state and in exercise (Phillipson, Bowes, Townsend, Duffin & Cooper, 1981). The further study of a putative chemical signal in the present preparation is described in the following paper (Cross, Davey, Guz, Katona, MacLean, Murphy, Semple, Stidwill, 1982 …”