Respiratory Influences on Acid-Base Status and Their Effects on O2 Transport during Prolonged Muscular Work

Dempsey, Jerome A.; Thomson, J. M.; Alexander, S. Craighead; Forster, H. V.; Chosy, L. W.

doi:10.1007/978-3-0348-5523-5_4

Cited by 7 publications

(3 citation statements)

References 12 publications

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“…Such hyperthermia induced at rest can itself cause sufficient hyperventilation in Man to lower PaCO 2 below 25 mmHg [ 71 , 72 ]. Moreover, preventing temperature rising during exercise at 1 kW prevents PaCO 2 falling from 40 to 30 mmHg [ 73 ].…”

Section: Do Carotid Chemoreceptors Mediate Just the Hyperventilatmentioning

confidence: 99%

Evaluating the Importance of the Carotid Chemoreceptors in Controlling Breathing during Exercise in Man

Parkes

2013

BioMed Research International

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Only the carotid chemoreceptors stimulate breathing during hypoxia in Man. They are also ideally located to warn if the brain's oxygen supply falls, or if hypercapnia occurs. Since their discovery ~80 years ago stimulation, ablation, and recording experiments still leave 3 substantial difficulties in establishing how important the carotid chemoreceptors are in controlling breathing during exercise in Man: (i) they are in the wrong location to measure metabolic rate (but are ideally located to measure any mismatch), (ii) they receive no known signal during exercise linking them with metabolic rate and no overt mismatch signals occur and (iii) their denervation in Man fails to prevent breathing matching metabolic rate in exercise. New research is needed to enable recording from carotid chemoreceptors in Man to establish whether there is any factor that rises with metabolic rate and greatly increases carotid chemoreceptor activity during exercise. Available evidence so far in Man indicates that carotid chemoreceptors are either one of two mechanisms that explain breathing matching metabolic rate or have no importance. We still lack key experimental evidence to distinguish between these two possibilities.

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Section: Do Carotid Chemoreceptors Mediate Just the Hyperventilatmentioning

confidence: 99%

Evaluating the Importance of the Carotid Chemoreceptors in Controlling Breathing during Exercise in Man

Parkes

2013

BioMed Research International

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“…In addition, the higher VE/VCO2 during moderate hypoxemia resulted in a lower level of bicarbonate and buffering capacity, as indicated by the low PETCC»2. Further, the quite low values of PETC02 seen during this condition imply hypocapnia which is known to reduce cerebral blood flow (Dempsey et al, 1975); the resulting neurobehavioral impairment (Hornbein et al, 1989) may have contributed to a diminished voluntary effort for maximum performance.…”

Section: Determination Of Hypoxemiamentioning

confidence: 95%

Arterial hypoxemia and performance during intense exercise

Koskolou

McKenzie

1994

Europ. J. Appl. Physiol.

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In order to determine the level of hypoxemia which is sufficient to impair maximal performance, seven well-trained male cyclists [maximum oxygen consumption (VO2max) > or = 5 l.min-1 or 60 ml.kg-1.min-1] performed a 5-min performance cycle test to exhaustion at maximal intensity as controlled by the subject, under three experimental conditions: normoxemia [percentage of arterial oxyhemoglobin saturation (%SaO2) > 94%], and artificially induced mild (%SaO2 = 90 +/- 1%) and moderate (% SaO2 = 87 +/- 1%) hypoxemia. Performance, evaluated as the total work output (Worktot) performed in the 5-min cycle test, progressively decreased with decreasing % SaO2 [mean (SE) Worktot = 107.40 (4.5) kJ, 104.07 (5.6) kJ, and 102.52 (4.7) kJ, under normoxemia, mild, and moderate hypoxemia, respectively]. However, only performance in the moderate hypoxemia condition was significantly different than in normoxemia (P = 0.02). Mean oxygen consumption and heart rate were similar in the three conditions (P = 0.18 and P = 0.95, respectively). End-tidal partial pressure of CO2 was significantly lower (P = 0.005) during moderate hypoxemia compared with normoxemia, and ventilatory equivalent of CO2 was significantly higher (P = 0.005) in both hypoxemic conditions when compared with normoxemia. It is concluded that maximal performance capacity is significantly impaired in highly trained cyclists working under an % SaO2 level of 87% but not under a milder desaturation level of 90%.

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“…During prolonged dynamic exercise at a constant workload in the heat, minute ventilation ( _ VE) increases progressively, suggesting that the increase could be associated with increasing body temperature (Dempsey et al 1975;Fujii et al 2008b, c;Hayashi et al 2004Hayashi et al , 2006Nybo and Nielsen 2001). We recently reported that _ VE increases in proportion to increasing core temperature during dynamic exercise at 50% of peak oxygen uptake ( _ VO 2peak ), although there was a great deal of individual variability in the ventilatory response to increasing body temperature (Hayashi et al 2006).…”

Section: Introductionmentioning

confidence: 95%

The cross-sectional relationships among hyperthermia-induced hyperventilation, peak oxygen consumption, and the cutaneous vasodilatory response during exercise

et al. 2009

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To test the hypothesis that the hyperthermia-induced ventilatory response relates to aerobic power and/or the cutaneous vasodilatory response during exercise, we asked 18 subjects to perform 3 kinds of exercise: an incremental exercise to determine peak oxygen consumption (V(O)(2peak)), a steady state exercise at 50% of V(O)(2peak) to determine the ventilatory response to increasing body temperature, and a steady state exercise at 60% of V(O)(2peak) to determine the cutaneous vasodilatory response to increasing body temperature. The ventilatory and cutaneous vasodilatory responses were evaluated by plotting the increase in minute ventilation or in forearm vascular conductance against the increase in oesophageal temperature. Regression analysis revealed that: (1) there was a negative relationship between the hyperthermic ventilatory response and cutaneous vasodilatory response, (2) there was a negative relationship between the hyperthermic ventilatory response and V(O)(2peak), and (3) there was a positive relationship between the cutaneous vasodilatory response and V(O)(2peak). These results support our hypothesis and suggest that exercise training suppresses the hyperthermic ventilatory response and improves the thermoregulatory response.

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Respiratory Influences on Acid-Base Status and Their Effects on O2 Transport during Prolonged Muscular Work

Cited by 7 publications

References 12 publications

Evaluating the Importance of the Carotid Chemoreceptors in Controlling Breathing during Exercise in Man

Evaluating the Importance of the Carotid Chemoreceptors in Controlling Breathing during Exercise in Man

Arterial hypoxemia and performance during intense exercise

The cross-sectional relationships among hyperthermia-induced hyperventilation, peak oxygen consumption, and the cutaneous vasodilatory response during exercise

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