Changes in peripheral chemoreflex sensitivity during sustained, isocapnic hypoxia

Bascom, Daphne A.; Clement, I; Cunningham, David A.; Painter, Rosemary; Robbins, Peter A.

doi:10.1016/0034-5687(90)90032-t

Cited by 52 publications

(34 citation statements)

References 15 publications

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“…The observation that the two responses are differentially affected (Fig. 4) would support the notion that anaesthetics act at a location before the stimuli have converged at the carotid body [37]. Dahan et al reached this same conclusion using a different (experimental) approach studying the relative dynamics of the hypoxic and hypercapnic responses with low dose anaesthetics [3,7,38].…”

Section: Site Of Action Of Anaestheticssupporting

confidence: 55%

“…It does not seem possible for the central nervous system to identify the type of stimulus to the carotid body but only its magnitude. It follows therefore that any intervention which acts on the chemoreflex primarily in the central nervous system should affect both acute hypoxic and hypercapnic responses equally since the two pathways are not distinct [37]. The observation that the two responses are differentially affected (Fig.…”

Section: Site Of Action Of Anaestheticsmentioning

confidence: 99%

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Effect of low dose inhaled anaesthetic agents on the ventilatory response to carbon dioxide in humans: a quantitative review

Pandit

2005

Anaesthesia

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SummaryThis paper reviews published studies (identified by a Medline-assisted search) on the effect of £ 0.2 minimum alveolar concentration inhaled anaesthetic agents on the hypercapnic ventilatory response in healthy subjects. Each article was examined for the anaesthetic agent used, whether CO 2 was administered using a rebreathing or a steady state (step hypercapnia) technique, and subject arousal (by audiovisual stimulation or by pain). Analysis of variance was used to assess the influence of each of these factors on the standardised hypercapnic response (the hypercapnic ventilatory response in l.min )1 .kPa )1 in the presence of anaesthetic, expressed as a fraction of the response without anaesthetic). There were 21 separate studies embedded within 14 published articles. When considered together, the effect of anaesthetics on the hypercapnic ventilatory response was not significant (p = 0.089). Furthermore, when each agent was considered separately, no agent alone had a significant effect on the hypercapnic response. Neither subject arousal (p = 0.396) nor the method used to induce hypercapnia (p = 0.625) had any significant influence on the response. This suggests that the hypercapnic response is more resistant to the effects of anaesthetics than the hypoxic ventilatory response. These results indicate areas for future work. It would seem important to identify the cellular mechanisms which might underlie the difference in hypercapnic and hypoxic responses, and possible ways in which subject arousal might interact in the brain with the chemoreflexes.

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Section: Site Of Action Of Anaestheticssupporting

confidence: 55%

Section: Site Of Action Of Anaestheticsmentioning

confidence: 99%

Effect of low dose inhaled anaesthetic agents on the ventilatory response to carbon dioxide in humans: a quantitative review

Pandit

2005

Anaesthesia

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“…However, as a result, the ventilatory response to hypoxia was less than that observed by other investigators where end-tidal partial pressures of carbon dioxide are often maintained 2-3 mmHg above resting (e.g. Bascom et al 1990;Berkenbosch et al 1992;Tansley et al 1998). Nonetheless, the repeated hypoxic exposures were still effective; demonstrating that hypoxia alone exerted an effect on the chemoreflexes, so that by the 14th day the initial ventilatory response to hypoxia and its subsequent decline were clearly discernible.…”

Section: Methodological Considerationsmentioning

confidence: 51%

“…The hypotheses involving the peripheral chemoreflex receive support from the observation that subjects with bilaterally resected carotid bodies lack a response to hypoxia (Honda, 1992;Kimura et al 1998). Bascom et al (1990) measured the ventilatory responses to brief pulses of additional hypoxia and hypercapnia during 23 min of sustained isocapnic hypoxia. Since both declined, they reasoned that the carotid bodies were involved, because a depression of the peripheral chemoreflex should affect both responses.…”

mentioning

confidence: 99%

Repeated hypoxic exposures change respiratory chemoreflex control in humans

Mahamed

Duffin

2001

The Journal of Physiology

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A group of seven volunteers (5 male, 2 female) were exposed to 20 min isocapnic (eucapnic) hypoxia once daily for 14 consecutive days. Their chemoreflexes were measured before and after each exposure. The same volunteers repeated the exposures with air substituted for the hypoxic gas mixture in a pseudorandom crossover design. On day 1 an initial ventilatory response to hypoxia and subsequent decline was discernible in two volunteers, but the mean response for all volunteers at this stage was not significant. However, the response gradually increased, and by day 14 was discernible in six volunteers making the mean response for all volunteers significant. No change was observed over the 14 days of air exposure. Only the chemoreflex threshold measured in iso‐oxic (hypoxic) modified rebreathing tests changed significantly, and only for the series of exposures to hypoxia. Over 14 days, the mean ±s.e.m. threshold for all volunteers fell proportionately, from 42 ± 1.1 mmHg on day 1 to 39 ± 1.0 mmHg on day 14. By contrast, the mean ±s.e.m. threshold, for all volunteers and all days, rose from 40 ± 0.4 mmHg before to 42 ± 0.5 mmHg after the hypoxic exposures. We conclude that the enhancement of the initial ventilatory response to hypoxia induced by repeated hypoxic exposure is produced by a decrease in chemoreflex threshold. However, the decline in the ventilatory response during a single exposure is produced by an increase in the chemoreflex threshold. Since threshold changes were only found for hypoxic (iso‐oxic) modified rebreathing tests, we conclude that only the peripheral chemoreflex changed.

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“…An effect on the off-sets should therefore be taken into consideration. Bascom et al (1990) investigated changes in peripheral chemoreflex loop activity during sustained hypoxia. They found that the ventilatory response due to extra hypoxic pulses at 17 min of hypoxia were significantly less than in the period before.…”

Section: Protocol Imentioning

confidence: 99%

The ventilatory response to CO2 of the peripheral and central chemoreflex loop before and after sustained hypoxia in man.

Berkenbosch

Dahan

DeGoede

et al. 1992

The Journal of Physiology

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SUMMARY1.The ventilatory response to sustained hypoxia is characterized by a fast increase due to the peripheral chemoreceptors followed by a slow decline. The mechanism of this decline is unknown.2. To investigate the characteristics of the ventilatory response to sustained hypoxia ten healthy subjects were exposed to two consecutive periods of isocapnic hypoxia (arterial saturation 78%) separated by a 5 min exposure to isocapnic normoxia.3. The acute hypoxic response to the second exposure to hypoxia (mean increase in ventilation + s.E.M., 7-2 + 08 1 min') was significantly depressed (P = 004) compared to the first one (9 5 + 1-3 1 min-). 4. To investigate whether this depression was due to central or-peripheral effects or both we measured, in the same ten subjects, the normoxic ventilatory response to CO2 before and after a period of 25 min of hypoxia using the technique of dynamic end-tidal forcing.5. Each response was separated into a fast peripheral and slow central component characterized by a CO2 sensitivity, time constant, time delay and an off-set.6. A total of thirty-six prehypoxic and thirty posthypoxic responses were analysed. The ventilatory CO2 sensitivities of the peripheral and central chemoreflex loops and the overall off-set (apnoeic threshold) after 25 min of hypoxia were somewhat larger than their prehypoxic values, but this effect was not significant. 7. We argue that the hypoxic ventilatory decline in man is due to a change in the off-set of the peripheral chemoreflex loop.

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Changes in peripheral chemoreflex sensitivity during sustained, isocapnic hypoxia

Cited by 52 publications

References 15 publications

Effect of low dose inhaled anaesthetic agents on the ventilatory response to carbon dioxide in humans: a quantitative review

Effect of low dose inhaled anaesthetic agents on the ventilatory response to carbon dioxide in humans: a quantitative review

Repeated hypoxic exposures change respiratory chemoreflex control in humans

The ventilatory response to CO2 of the peripheral and central chemoreflex loop before and after sustained hypoxia in man.

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