The Contribution of Chemoreflex Drives to Resting Breathing in Man

Mahamed, Safraaz; Ali, Arshia F.; Ho, Dominic; Wang, Bernice; Duffin, James

doi:10.1113/eph8602090

Cited by 34 publications

(22 citation statements)

References 23 publications

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“…The values that were obtained for the chemoreflex ventilation threshold and sensitivity in the current research are similar to those our laboratory reported previously (Mahamed et al 2001). Results regarding the effect of training on the chemoreflex ventilation threshold obtained during rebreathing have not been reported previously in the literature.…”

Section: Chemoreflex Responsesupporting

confidence: 70%

Effects of concurrent inspiratory and expiratory muscle training on respiratory and exercise performance in competitive swimmers

et al. 2005

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The efficiency of the respiratory system presents significant limitations on the body's ability to perform exercise due to the effects of the increased work of breathing, respiratory muscle fatigue, and dyspnoea. Respiratory muscle training is an intervention that may be able to address these limitations, but the impact of respiratory muscle training on exercise performance remains controversial. Therefore, in this study we evaluated the effects of a 12-week (10 sessions week(-1)) concurrent inspiratory and expiratory muscle training (CRMT) program in 34 adolescent competitive swimmers. The CRMT program consisted of 6 weeks during which the experimental group (E, n = 17) performed CRMT and the sham group (S, n = 17) performed sham CRMT, followed by 6 weeks when the E and S groups performed CRMT of differing intensities. CRMT training resulted in a significant improvement in forced inspiratory volume in 1 s (FIV1.0) (P = 0.050) and forced expiratory volume in 1 s (FEV1.0) (P = 0.045) in the E group, which exceeded the S group's results. Significant improvements in pulmonary function, breathing power, and chemoreflex ventilation threshold were observed in both groups, and there was a trend toward an improvement in swimming critical speed after 12 weeks of training (P = 0.08). We concluded that although swim training results in attenuation of the ventilatory response to hypercapnia and in improvements in pulmonary function and sustainable breathing power, supplemental respiratory muscle training has no additional effect except on dynamic pulmonary function variables.

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Section: Chemoreflex Responsesupporting

confidence: 70%

Effects of concurrent inspiratory and expiratory muscle training on respiratory and exercise performance in competitive swimmers

et al. 2005

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“…Although the use of respiratory equilibrium diagram has been described by Mahamed et al (2001), there is no report of experimental study in humans that quantitatively validates the major mechanism of exercise hyperpnea based on integration of the controller and plant properties in the respiratory equilibrium diagram.…”

Section: Introductionmentioning

confidence: 98%

Adaptation of the respiratory controller contributes to the attenuation of exercise hyperpnea in endurance-trained athletes

et al. 2011

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We have reported that minute ventilation [[Formula: see text]] and end-tidal CO(2) tension [[Formula: see text]] are determined by the interaction between central controller and peripheral plant properties. During exercise, the controller curve shifts upward with unchanged central chemoreflex threshold to compensate for the plant curve shift accompanying increased metabolism. This effectively stabilizes [Formula: see text] within the normal range at the expense of exercise hyperpnea. In the present study, we investigated how endurance-trained athletes reduce this exercise hyperpnea. Nine exercise-trained and seven untrained healthy males were studied. To characterize the controller, we induced hypercapnia by changing the inspiratory CO(2) fraction with a background of hyperoxia and measured the linear [Formula: see text] relation [[Formula: see text]]. To characterize the plant, we instructed the subjects to alter [Formula: see text] voluntarily and measured the hyperbolic [Formula: see text] relation ([Formula: see text]). We characterized these relations both at rest and during light exercise. Regular exercise training did not affect the characteristics of either controller or plant at rest. Exercise stimulus increased the controller gain (S) both in untrained and trained subjects. On the other hand, the [Formula: see text]-intercept (B) during exercise was greater in trained than in untrained subjects, indicating that exercise-induced upward shift of the controller property was less in trained than in untrained subjects. The results suggest that the additive exercise drive to breathe was less in trained subjects, without necessarily a change in central chemoreflex threshold. The hyperbolic plant property shifted rightward and upward during exercise as predicted by increased metabolism, with little difference between two groups. The [Formula: see text] during exercise in trained subjects was 21% lower than that in untrained subjects (P < 0.01). These results indicate that an adaptation of the controller, but not that of plant, contributes to the attenuation of exercise hyperpnea at an iso-metabolic rate in trained subjects. However, whether training induces changes in neural drive originating from the central nervous system, afferents from the working limbs, or afferents from the heart, which is additive to the chemoreflex drive to breathe, cannot be determined from these results.

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“…1B), quantitative analysis of both subsystems can determine how changes in both the controller and plant elements affect V E or Pa CO 2 (5,6,17,18,41,45,46,48); however, to what extent changes in central blood volume (CBV) influence these variables and thus, by consequence, the operating point (V E or Pa CO 2 response) of the respiratory control system remain unclear.…”

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confidence: 99%

“…It can be divided into two subsystems (Fig. 1A): a controller (controlling element) and a plant (controlled element) (5,17,18,21,35,41,45,46).Recently, we have characterized these subsystem elements in an open-loop condition and constructed a respiratory equilibrium diagram to illustrate the mechanisms of respiratory control at rest and during exercise in endurance-trained and untrained subjects (46,48,52). Briefly, the controller element approximates a straight line where minute ventilation (V E) increases as a function of Pa CO 2 .…”

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confidence: 99%

Manipulation of central blood volume and implications for respiratory control function

Miyamoto

Bailey

Nakahara

et al. 2014

American Journal of Physiology-Heart and Circulatory Physiology

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The respiratory operating point (ventilatory or arterial PCO 2 response) is determined by the intersection point between the controller and plant subsystem elements within the respiratory control system. However, to what extent changes in central blood volume (CBV) influence these two elements and the corresponding implications for the respiratory operating point remain unclear. To examine this, 17 apparently healthy male participants were exposed to water immersion (WI) or lower body negative pressure (LBNP) challenges to manipulate CBV and determine the corresponding changes. The respiratory controller was characterized by determining the linear relationship between end-tidal PCO 2 (PETCO 2 ) and minute ventilation (V E) [V E ϭ S ϫ (PET CO 2 Ϫ B)], whereas the plant was determined by the hyperbolic relationship between V E and PETCO 2 (PETCO 2 ϭ A/V E ϩ C). Changes in V E at the operating point were not observed under either WI or LBNP conditions despite altered PET CO 2 (P Ͻ 0.01), indicating a moving respiratory operating point. An increase (WI) and a decrease (LBNP) in CBV were shown to reset the controller element (PETCO 2 intercept B) rightward and leftward, respectively (P Ͻ 0.05), without any change in S, whereas the plant curve remained unaltered at the operating point. Collectively, these findings indicate that modification of the controller element rather than the plant element is the major factor that contributes toward an alteration of the respiratory operating point during CBV shifts. system analysis; respiratory control; central blood volume; head-out water immersion; lower body negative pressure THE RESPIRATORY SYSTEM is an important chemoreflex-feedback control system that maintains arterial PCO 2 (Pa CO 2 ), O 2 , and pH remarkably constant via ventilatory regulation. It can be divided into two subsystems (Fig. 1A): a controller (controlling element) and a plant (controlled element) (5,17,18,21,35,41,45,46).Recently, we have characterized these subsystem elements in an open-loop condition and constructed a respiratory equilibrium diagram to illustrate the mechanisms of respiratory control at rest and during exercise in endurance-trained and untrained subjects (46,48,52). Briefly, the controller element approximates a straight line where minute ventilation (V E) increases as a function of Pa CO 2 . The element can be broadly divided into chemoreflex and nonchemoreflex drives to breathe (39). The plant element approximates a hyperbola with a positive asymptote where Pa CO 2 decreases asymptotically as a function of V E (APPENDIX).Since respiration is determined from an intersection point between these two elements on the respiratory equilibrium diagram (Fig. 1B), quantitative analysis of both subsystems can determine how changes in both the controller and plant elements affect V E or Pa CO 2 (5,6,17,18,41,45,46,48); however, to what extent changes in central blood volume (CBV) influence these variables and thus, by consequence, the operating point (V E or Pa CO 2 response) of the respiratory co...

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The Contribution of Chemoreflex Drives to Resting Breathing in Man

Cited by 34 publications

References 23 publications

Effects of concurrent inspiratory and expiratory muscle training on respiratory and exercise performance in competitive swimmers

Effects of concurrent inspiratory and expiratory muscle training on respiratory and exercise performance in competitive swimmers

Adaptation of the respiratory controller contributes to the attenuation of exercise hyperpnea in endurance-trained athletes

Manipulation of central blood volume and implications for respiratory control function

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