The influence of hyperventilation on efferent control of peripheral chemoreceptors

Majcherczyk, S; Willshaw, Peter

doi:10.1016/0006-8993(77)90957-x

Cited by 13 publications

(2 citation statements)

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“…In addition, the hypocapnia presumably causes a reduction in cerebrospinal fluid PCo2, a condition which may restrain the activity of the central chemoreceptors. A further source of ventilatory constraint may also arise from an efferent inhibitory pathway which, in the cat, has been shown to project from the brain stem to the carotid body by way of the carotid sinus nerve (Neil & O'Regan, 1971), and which can be activated by an increase in cerebrospinal fluid pH (Majcherczyk & Willshaw, 1977). Regardless of the magnitude of such influences, however, the hyperpnoeic drive induced during the isometric exercise in (Table 2 and Fig.…”

Section: Discussionmentioning

confidence: 99%

Control of blood‐gas and acid‐base status during isometric exercise in humans.

Poole¹,

Ward²,

Whipp³

1988

The Journal of Physiology

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SUMMARY 1. At a given level of pulmonary gas exchange, ventilation (VE) is appreciably higher during isometric exercise than during isotonic exercise. It is presently not clear whether the resultant hypocapnia represents a compensatory hyperventilation for an arterial metabolic acidaemia or whether it might reflect a primary respiratory alkalaemia.2. To resolve this issue, five subjects performed isometric leg exercise designed to induce exhaustion in ca. 5 min and, on a separate occasion, ca. 8 min. VE, CO2 output (VCO), 02 uptake (VO ) and end-tidal gas tensions (PET,CO,, PET,O2) were measured breath-by-breath during exercise and recovery; arterialized venous blood (drawn from the dorsum of the heated hand) was sampled frequently and analysed for Pco, PO2, pH, bicarbonate and lactate. These response profiles were compared with those resulting from exhausting bouts of isotonic leg exercise (cycle ergometry) of similar duration.3. The isotonic exercise induced a metabolic (lactic) acidaemia with partial respiratory compensation. In contrast, isometric exercise consistently resulted in a respiratory alkalaemia, with little or no increase of blood [lactate]. At the end of the isometric exercise, VE fell abruptly and then rose again after a short interval (20 s, on average). This secondary stimulation presumably reflected the acid-base consequences of the increased blood [lactate] (3-5 mm, on average) which occurred in the recovery phase.4. We therefore conclude that a primary respiratory alkalaemia occurs during isometric exercise, and that this results from ventilatory stimulation at a time when the 'exercise' metabolites are trapped within the contracting muscles as a consequence of impeded blood flow. The initial rapid reduction of ventilation which occurred at the cessation of the isometric exercise is consistent with a washing-out of 'hyperpnoea-inducing' metabolites from the muscles. Allowing for transit to the central circulation, the reduced ventilation is subsequently supplemented by a powerful humoral drive to breathe which results in a further hyperpnoea and secondary hypocapnia. Because of its latency, we hypothesize that this secondary hypocapnia is of peripheral chemoreceptor origin.5.

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Section: Discussionmentioning

confidence: 99%

Control of blood‐gas and acid‐base status during isometric exercise in humans.

Poole¹,

Ward²,

Whipp³

1988

The Journal of Physiology

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show abstract

“…Other pressor agents such as NE, vasopressin (54), and angiotensin (563) also increase the efferent discharge frequency, as does a transfusion of blood that mechanically elevates the systemic arterial pressure (563). Other stimuli of efferent activity in the cat are perfusion of the ventral surface of the medulla with alkaline cerebrospinal fluid (394,396,562) and hypocapnia produced by hyperventilation, reducing the end tidal fraction of COn to about 2% (396). Apparently the afferent traffic in the nerve may reflexly stimulate efferent activity.…”

Section: Sources Of E F F E R E N T Activity I N Carotidmentioning

confidence: 99%