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The pH oscillations in arterial blood during exercise; a potential signal for the ventilatory response in the dog
Author(s) -
Cross Brenda A.,
Davey A.,
Guz A.,
Katona P. G.,
Maclean M.,
Murphy K.,
Semple S. J. G.,
Stidwill R.
Publication year - 1982
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1982.sp014290
Subject(s) - arterial blood , cardiology , medicine , signal (programming language) , anesthesia , neuroscience , biology , computer science , programming language
1. The effect of electrically induced ‘exercise’ on the respiratory oscillation of arterial pH was studied in chloralose‐anaesthetized dogs with spinal cord transection at T8/9 (dermatome level T6/7). 2. Respiratory oscillations of arterial pH (presumed to be due to oscillations of arterial P CO2 ) 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/d t ↓max) 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 CO 2 ; the Δ V̇ I /Δ P a, CO2 was significantly greater for ‘exercise’ than for CO 2 inhalation. 4. On average, the amplitude of the pH oscillations decreased during ‘exercise’. The change in the phase relationship (ϕ) between respiratory and pH cycles, although significant from the second breath onwards, was not thought to be responsible for the increased ventilation V̇ I ; the direction of the change was opposite to that previously found to increase V̇ I . 5. Inspiratory duration ( t i ), expiratory duration ( t e ), V̇ I and the dpH/d t ↓max changed significantly by the third breath of ‘exercise’. A significantly linear relationship was obtained between t e and dpH/d t ↓max during the on‐transient (first ten breaths) of ‘exercise’. This relationship was maintained throughout ‘exercise’. V̇ I and dpH/d t ↓max were also linearly related during the on‐transient, although the same relationship did not hold true throughout ‘exercise’. 6. The dpH/d t ↓max was related to CO 2 production ( V̇ CO2 ) lending support to the prediction that the slope of the downstroke of the pH oscillation is a function of V̇ CO2 . 7. It was concluded that the dpH/d t ↓max (dpCO 2 /d t ↑max) is a potential humoral signal in ‘exercise’ and could account totally for the shortening of t e . Since there was a late rise in V̇ I (due to an increase in tidal volume V T ) in the absence of a change in dpH/d t ↓max, it was considered unlikely that the dpH/d t ↓max was the only humoral signal present during ‘exercise’.