The effects of head-up and head-down tilt on central respiratory chemoreflex loop gain tested by hyperoxic rebreathing

Skow, Rachel J.; Tymko, Michael M.; MacKay, Christina M.; Steinback, Craig D.; Day, Trevor A.

doi:10.1016/b978-0-444-63488-7.00009-4

Cited by 12 publications

(17 citation statements)

References 86 publications

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“…In addition, because these

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gradients are assumed to be reduced or eliminated, the effects of cerebrovascular reactivity on central chemoreceptor stimulation are eliminated; thus, the magnitude of the central respiratory chemoreflex more closely approximates the intrinsic chemoreceptor sensitivity of the individual (Skow et al . ). Accordingly, the central chemoreflex magnitude appears to be lower using steady‐state techniques compared with rebreathing, probably owing to the effects of CO 2 washout from brainstem tissue, because the cerebrovasculature also responds to the CO 2 stimulus during the steady‐state test.…”

Section: Discussionmentioning

confidence: 97%

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Influence of prior hyperventilation duration on respiratory chemosensitivity and cerebrovascular reactivity during modified hyperoxic rebreathing

Boulet

Tymko

Jamieson

et al. 2016

Experimental Physiology

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New Findings r What is the central question of this study?We characterized and compared the cardiorespiratory and cerebrovascular responses to the 'Duffin' modified hyperoxic CO 2 rebreathing test by randomly altering the prior hyperventilation duration. r What is the main finding and its importance?Our main finding was that prior hyperventilation duration (1, 3 or 5 min) had no effect on cardiorespiratory and cerebrovascular responses to the hyperoxic rebreathing test, within individuals. These findings suggest that the standard 5 min prior hyperventilation duration used to clear body CO 2 stores is unnecessary and can reasonably be shortened to 1 min, reducing protocol times and improving participant comfort.The 'Duffin' modified hyperoxic rebreathing test allows investigators to characterize and quantify the ventilatory and cerebrovascular responses to CO 2 across a large physiological range, allowing quantification of basal ventilation and the ventilatory recruitment threshold (VRT). Although the standard protocol includes 5 min of prior hyperventilation to clear body CO 2 stores, there is no experimental evidence that a full 5 min is required. We hypothesized that there would be no within-individual differences in the cardiorespiratory or cerebrovascular responses to rebreathing with shortened hyperventilation duration prior to hyperoxic rebreathing. Using a rebreathing apparatus, transcranial Doppler ultrasound and beat-to-beat blood pressure monitoring, we tested 19 participants in the supine position using three randomly assigned hyperoxic rebreathing tests with 1, 3 or 5 min of prior hyperventilation. We measured VRT (in Torr CO 2 ), time to VRT (in seconds), central respiratory chemoreflex (breathing frequency, tidal volume and minute ventilation), cerebrovascular (middle and posterior cerebral artery velocity) and cardiovascular (heart rate and mean arterial pressure) responses to CO 2 during hyperoxic rebreathing. Using linear regression and repeated-measures ANOVAs, we found no differences in any of the cardiorespiratory or cerebrovascular response magnitudes between trials (P > 0.05). The only difference observed was in the time to VRT (in seconds), whereby 1 min prior hyperventilation duration was shorter (135.4 ± 19.7 s) than with 3 or 5 min prior

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“…In addition, because these

P_{normalC O_{2}}

Section: Discussionmentioning

confidence: 97%

“…; Skow et al . ). Although the modified rebreathing test was developed for the quantification of additional respiratory variables (e.g., VRT), prior hyperventilation can be used to reduced body CO 2 stores and increase the range across which the cerebrovascular responses are quantified.…”

Section: Discussionmentioning

confidence: 97%

Influence of prior hyperventilation duration on respiratory chemosensitivity and cerebrovascular reactivity during modified hyperoxic rebreathing

Boulet

Tymko

Jamieson

et al. 2016

Experimental Physiology

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“…Mechanisms leading to reduced ventilatory oscillations under ACZ are still debated. This may involve a third arm, the mixing gain, depending, among other factors, on cerebral blood flow which might increase the CO 2 washout of the cerebral spinal fluid and therefore blunt ventilatory oscillations (Younes et al 2001;Dempsey et al 2004;Skow et al 2014). However, both exercise (Ogoh and Ainslie 2009) and ACZ (Okazawa et al 2001) are known to increase cerebral blood flow but have opposite effects on breathing instability (this study).…”

Section: Mechanismsmentioning

confidence: 99%

Ventilatory oscillations at exercise: effects of hyperoxia, hypercapnia, and acetazolamide

et al. 2015

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Periodic breathing has been found in patients with heart failure and sleep apneas, and in healthy subjects in hypoxia, during sleep and wakefulness, at rest and, recently, at exercise. To unravel the cardiorespiratory parameters liable to modulate the amplitude and period of ventilatory oscillations, 26 healthy subjects were tested under physiological (exercise) and environmental (hypoxia, hyperoxia, hyperoxic hypercapnia) stresses, and under acetazolamide (ACZ) treatment. A fast Fourier transform spectral analysis of breath-by-breath ventilation evidenced an increase in peak power under hypercapnia (vs. normoxia and hyperoxia, P < 0.001) and a decrease under ACZ (vs. placebo, P < 0.001), whereas it was not modified in hyperoxia. period was shortened by exercise in all conditions (vs. rest, P < 0.01) and by hypercapnia (vs. normoxia, P < 0.05) but remained unchanged under ACZ (vs. placebo). peak power was positively related to cardiac output () and in hyperoxia (P < 0.01), in hypercapnia (P < 0.001) and under ACZ (P < 0.001). period was negatively related to and in hyperoxia (P < 0.01 and P < 0.001, respectively), in hypercapnia (P < 0.05 and P < 0.01, respectively) and under ACZ (P < 0.05 and P < 0.01, respectively). Total respiratory cycle time was the main factor responsible for changes in period. In conclusion, exercise, hypoxia, and hypercapnia increase ventilatory oscillations by increasing and , whereas ACZ decreases ventilatory instability in part by a contrasting action on O2 and CO2 sensing. An intrinsic oscillator might modulate ventilation through a complex system where peripheral chemoreflex would play a key role.

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“…In addition, the hyperoxia effectively silences the peripheral chemoreceptors (e.g. Read, 1967;Lahiri & Delaney, 1975;Casey et al 1987;Daristotle et al 1987;Duffin, 2011;Skow et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Comparing and characterizing transient and steady‐state tests of the peripheral chemoreflex in humans

Pfoh

Tymko

Abrosimova

et al. 2016

Experimental Physiology

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The effects of head-up and head-down tilt on central respiratory chemoreflex loop gain tested by hyperoxic rebreathing

Cited by 12 publications

References 86 publications

Influence of prior hyperventilation duration on respiratory chemosensitivity and cerebrovascular reactivity during modified hyperoxic rebreathing

Influence of prior hyperventilation duration on respiratory chemosensitivity and cerebrovascular reactivity during modified hyperoxic rebreathing

Ventilatory oscillations at exercise: effects of hyperoxia, hypercapnia, and acetazolamide

Comparing and characterizing transient and steady‐state tests of the peripheral chemoreflex in humans

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