Respiratory Compensation Point during Incremental Exercise as Related to Hypoxic Ventilatory Chemosensitivity and Lactate Increase in Man.

Abstract

During incremental exercise in normal humans, pulmonary ventilation (V E) linearly increases with increasing O 2 uptake (V O 2 ), but the increment of V E against V O 2 becomes steeper at two V O 2 points [1]. The first inflection point, occurring at a lower V O 2 , is termed the ventilatory threshold (VT) [2], above which various kinds of ventilatory stimuli such as a fall in arterial pH due to lactic acidosis, hyperkalemia and augumentation of arterial PCO 2 oscillation are newly induced [3][4][5][6]. With further increases in the ventilatory stimuli as exercise becomes heavier, a steeper increase in V E against V O 2 occurs. The V O 2 point of the onset of this V E augmentation is termed the respiratory compensation point (RCP), above which the V E augmentation (hyperventilation) induces a fall in arterial PCO 2 , with resulting constraint of further falls of arterial pH due to severer lactic acidosis [7]. Peripheral chemoreceptors have been implicated as the site at which the ventilatory stimuli act because of the absence of compensatory hyperventilation and subsequent fall in PCO 2 during heavy exercise in carotid body-resected patients [8,9]. Japanese Journal of Physiology, 50, 449-455, 2000 Key words: heavy exercise, respiratory compensation point, exercise hyperpnea, carotid body, lactic acidosis. Abstract:The pulmonary ventilation-O 2 uptake (V E-V O 2 ) relationship during incremental exercise has two inflection points: one at a lower V O 2 , termed the ventilatory threshold (VT); and another at a higher V O 2 , the respiratory compensation point (RCP). The individuality of RCP was studied in relation to those of the chemosensitivities of the central and peripheral chemoreceptors, which were assessed by resting estimates of hypercapnic ventilatory response (HCVR) and hypoxic ventilatory response (HVR), respectively, and the rate of lactic acid increase during exercise, which was estimated as a slope difference (⌬slope) between a lower slope of V CO 2 -V O 2 relationship (V CO 2 : CO 2 output) obtained at work rates below VT and a higher slope at work rates between VT and RCP. Twenty-two male and sixteen female subjects underwent a 1 min incremental exercise test until exhaustion, in which VT, RCP and ⌬slope were determined. All measures were normalized for body surface area. In the males, the individual difference in RCP was inversely correlated with those of HVR and ⌬slope (pϽ0.05), and in the females, similar tendencies persisted, while the correlation did not reach statistically significant levels (0.05ϽpϽ 0.1). There was no significant correlation between RCP and HCVR in either sex. A multiple linear regression analysis showed that 40 to 50% of the variance of RCP was accounted for by those of HVR and ⌬slope, both of which were related linearly and additively to RCP, this relation being manifested in the males but not in the females without consideration of the menstrual cycle. These results suggest that the individuality of RCP depends partly on the chemosensitivity of the carotid bodies and th...

Evidence of break-points in breathing pattern at the gas-exchange thresholds during incremental cycling in young, healthy subjects

“…We speculate that the characteristic changes in breathing pattern observed at the gas-exchange thresholds may result from: (1) chemoreceptor stimulation due to metabolic acidosis; (2) the expression of the 'mammalian' panting strategy; (3) corollary activation of respiratory centres secondary to increased central and peripheral neurogenic stimuli; (4) an abrupt decline in cerebral oxygenation; and/ or (5) the evocation of the Hering-Breuer 'inflation reflex'-these phenomena are believed to correspond to the gas-exchange thresholds during incremental cycling (Benito et al 2006;Bhambhani et al 2007;Hug et al 2003;Takano 2000;White and Cabanac 1996). Our findings point to the involvement of the 'inflation reflex' in the abrupt changes in breathing pattern (at least in V T ) observed at exercise-intensities corresponding to the G EX 2 .…”

Mitochondrial efficiency and exercise economy following heat stress: a potential role of uncoupling protein 3

“…). Ventilatory threshold (VT) was determined by an increase in Ve/VO 2 with no change in Ve/VCO 2 (Davis ), while the respiratory compensation point (RCP) was defined as simultaneous increase in Ve/VO 2 and Ve/VCO 2 (Takano ).…”

Clinical significance of respiratory compensation during exercise testing in cardiac patients

“…Agree with Nariko Takano (21), we suppose that this hyperventilate in non-RC patients may attributed to the hypersensitivity of carotid body. The previous research by Nariko Takano suggest that the individuality of RC point depends partly on the rate of lactic acid increase and chemosensitivity of the carotid bodies during incremental exercise (21). The latter, in turn, may be related to sympathetic overactivity or altered central command (22,23).…”