Cardiovascular effects of the respiratory muscle metaboreflexes in dogs:  rest and exercise

Rodman, J. R.; Henderson, K. S.; Smith, Curtis A.; Dempsey, Jerome A.

doi:10.1152/japplphysiol.00258.2003

Cited by 71 publications

(80 citation statements)

References 47 publications

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“…In canines exercising at moderate work intensities, a bolus infusion of lactic acid into either the phrenic artery or the deep circumflex iliac artery elicited a transient reduction in limb blood flow and vascular conductance (102). Again, these vascular responses appeared to be sympathetically mediated because they were prevented by pharmacological blockade of the adrenergic receptors (102).…”

Section: Mechanisms By Which Respiratory Muscle Fatigue Could Affect mentioning

confidence: 99%

“…Diaphragm fatigue caused a timedependent increase in multiunit activity in small-diameter phrenic afferents in anesthetized cats (15,49) and in single-unit activity in group IV afferents in anesthetized rats (45). Furthermore, when metaboreceptors in the diaphragm or expiratory muscles were stimulated electrically, pharmacologically, or with local lactic acid infusions, efferent sympathetic nerve activity increased and vascular conductance decreased in several vascular beds, including those in limb muscle (48,96,102).…”

Section: Mechanisms By Which Respiratory Muscle Fatigue Could Affect mentioning

confidence: 99%

“…It appears likely that the local reductions in vascular conductance were sympathetically mediated because these changes were inversely correlated with changes in norepinephrine spillover across the working limb (39). In canines exercising at moderate work intensities, a bolus infusion of lactic acid into either the phrenic artery or the deep circumflex iliac artery elicited a transient reduction in limb blood flow and vascular conductance (102). Again, these vascular responses appeared to be sympathetically mediated because they were prevented by pharmacological blockade of the adrenergic receptors (102).…”

Section: Mechanisms By Which Respiratory Muscle Fatigue Could Affect mentioning

confidence: 99%

“…(102). Furthermore, expiratory flow limitation and prolonged expiratory time during heavy exercise often result in positive intrathoracic pressures that meet or exceed those at which dynamic compression of the airways occurs (54).…”

Section: Mechanisms By Which Respiratory Muscle Fatigue Could Affect mentioning

confidence: 99%

“…Respiratory muscle work had to be increased to near fatiguing levels for muscle sympathetic nerve activity to be increased (22,120), or for blood flow to be decreased in a resting (109) or an exercising limb (39,59,102,139). Exercise in hypoxia would also be expected to exacerbate the effects of respiratory muscle work on limb fatigue and exercise tolerance.…”

Section: Conditions Under Which Respiratory Muscle Work Affects Limb mentioning

confidence: 99%

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Exercise-induced respiratory muscle fatigue: implications for performance

Romer

Polkey²

2008

Journal of Applied Physiology

244

212

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Romer LM, Polkey MI. Exercise-induced respiratory muscle fatigue: implications for performance. J Appl Physiol 104: 879 -888, 2008. First published December 20, 2007 doi:10.1152/japplphysiol.01157.2007.-It is commonly held that the respiratory system has ample capacity relative to the demand for maximal O 2 and CO2 transport in healthy humans exercising near sea level. However, this situation may not apply during heavy-intensity, sustained exercise where exercise may encroach on the capacity of the respiratory system. Nerve stimulation techniques have provided objective evidence that the diaphragm and abdominal muscles are susceptible to fatigue with heavy, sustained exercise. The fatigue appears to be due to elevated levels of respiratory muscle work combined with an increased competition for blood flow with limb locomotor muscles. When respiratory muscles are prefatigued using voluntary respiratory maneuvers, time to exhaustion during subsequent exercise is decreased. Partially unloading the respiratory muscles during heavy exercise using low-density gas mixtures or mechanical ventilation can prevent exercise-induced diaphragm fatigue and increase exercise time to exhaustion. Collectively, these findings suggest that respiratory muscle fatigue may be involved in limiting exercise tolerance or that other factors, including alterations in the sensation of dyspnea or mechanical load, may be important. The major consequence of respiratory muscle fatigue is an increased sympathetic vasoconstrictor outflow to working skeletal muscle through a respiratory muscle metaboreflex, thereby reducing limb blood flow and increasing the severity of exerciseinduced locomotor muscle fatigue. An increase in limb locomotor muscle fatigue may play a pivotal role in determining exercise tolerance through a direct effect on muscle force output and a feedback effect on effort perception, causing reduced motor output to the working limb muscles. respiratory muscles; exercise; diaphragm; abdominals; magnetic stimulation; metaboreflex THE PURPOSE OF THIS MINIREVIEW is to address the question of whether the respiratory demands of exercise contribute significantly toward exercise limitation, either directly through limitations of the respiratory muscle pump or indirectly through effects on limb blood flow and locomotor muscle fatigue. We describe the mechanical and metabolic costs of meeting the ventilatory requirements of exercise. We then ask whether the respiratory muscles fatigue with exercise, what factors contribute to any such fatigue, and what the implications of these factors are for exercise tolerance. Finally, we deal with the potential mechanisms by which respiratory muscle fatigue could compromise exercise tolerance and whether it is possible to overcome this potential respiratory limitation. Our review focuses on the healthy young adult exercising near sea level. However, we also consider special circumstances that determine the balance between metabolic demand and respiratory system capacity in the highly trained endurance ...

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Section: Mechanisms By Which Respiratory Muscle Fatigue Could Affect mentioning

confidence: 99%

Section: Mechanisms By Which Respiratory Muscle Fatigue Could Affect mentioning

confidence: 99%

Section: Mechanisms By Which Respiratory Muscle Fatigue Could Affect mentioning

confidence: 99%

Section: Mechanisms By Which Respiratory Muscle Fatigue Could Affect mentioning

confidence: 99%

Section: Conditions Under Which Respiratory Muscle Work Affects Limb mentioning

confidence: 99%

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Exercise-induced respiratory muscle fatigue: implications for performance

Romer

Polkey²

2008

Journal of Applied Physiology

244

212

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Control of Breathing During Exercise

Forster

Haouzi

Dempsey

2012

Comprehensive Physiology

Self Cite

183

203

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During exercise by healthy mammals, alveolar ventilation and alveolar-capillary diffusion increase in proportion to the increase in metabolic rate to prevent PaCO2 from increasing and PaO2 from decreasing. There is no known mechanism capable of directly sensing the rate of gas exchange in the muscles or the lungs; thus, for over a century there has been intense interest in elucidating how respiratory neurons adjust their output to variables which can not be directly monitored. Several hypotheses have been tested and supportive data were obtained, but for each hypothesis, there are contradictory data or reasons to question the validity of each hypothesis. Herein, we report a critique of the major hypotheses which has led to the following conclusions. First, a single stimulus or combination of stimuli that convincingly and entirely explains the hyperpnea has not been identified. Second, the coupling of the hyperpnea to metabolic rate is not causal but is due to of these variables each resulting from a common factor which link the circulatory and ventilatory responses to exercise. Third, stimuli postulated to act at pulmonary or cardiac receptors or carotid and intracranial chemoreceptors are not primary mediators of the hyperpnea. Fourth, stimuli originating in exercising limbs and conveyed to the brain by spinal afferents contribute to the exercise hyperpnea. Fifth, the hyperventilation during heavy exercise is not primarily due to lactacidosis stimulation of carotid chemoreceptors. Finally, since volitional exercise requires activation of the CNS, neural feed-forward (central command) mediation of the exercise hyperpnea seems intuitive and is supported by data from several studies. However, there is no compelling evidence to accept this concept as an indisputable fact.

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Ventilation and Respiratory Mechanics

Sheel

Romer

2012

Comprehensive Physiology

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During dynamic exercise, the healthy pulmonary system faces several major challenges, including decreases in mixed venous oxygen content and increases in mixed venous carbon dioxide. As such, the ventilatory demand is increased, while the rising cardiac output means that blood will have considerably less time in the pulmonary capillaries to accomplish gas exchange. Blood gas homeostasis must be accomplished by precise regulation of alveolar ventilation via medullary neural networks and sensory reflex mechanisms. It is equally important that cardiovascular and pulmonary system responses to exercise be precisely matched to the increase in metabolic requirements, and that the substantial gas transport needs of both respiratory and locomotor muscles be considered. Our article addresses each of these topics with emphasis on the healthy, young adult exercising in normoxia. We review recent evidence concerning how exercise hyperpnea influences sympathetic vasoconstrictor outflow and the effect this might have on the ability to perform muscular work. We also review sex-based differences in lung mechanics.

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Cardiovascular effects of the respiratory muscle metaboreflexes in dogs: rest and exercise

Cited by 71 publications

References 47 publications

Exercise-induced respiratory muscle fatigue: implications for performance

Exercise-induced respiratory muscle fatigue: implications for performance

Control of Breathing During Exercise

Ventilation and Respiratory Mechanics

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