Respiratory muscle work influences locomotor convective and diffusive oxygen transport in human heart failure during exercise

Smith, Joshua R.; Berg, Jessica D.; Curry, Timothy B.; Joyner, Michael J.; Olson, Thomas P.

doi:10.14814/phy2.14484

Cited by 7 publications

(4 citation statements)

References 21 publications

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“…The pulmonary system is responsible for the transport of O 2 from the atmosphere to the bloodstream, with alveolar ventilation (O 2 exchange with the atmosphere) and diffusion (O 2 exchange with the bloodstream) contributing to arterial O 2 content, O 2 delivery, and VO 2 peak (68). Reduced alveolar exchange can be a significant contributor to exercise intolerance in patients with HF, which can occur due to impaired pulmonary vasodilation, ventilation/perfusion mismatch, impaired diffusion, abnormal ventilatory reserve (i.e., respiratory muscle dysfunction), or abnormal ventilatory regulation (i.e., oscillatory patterns) (102)(103)(104)(105). Furthermore, respiratory muscle fatigue has also been shown to affect O 2 delivery by causing peripheral vasoconstriction and reduced blood flow to skeletal muscles, further exacerbating exercise intolerance (106).…”

Section: Pulmonary Adaptationsmentioning

confidence: 99%

Optimizing Outcomes in Cardiac Rehabilitation: The Importance of Exercise Intensity

Taylor

Bonikowske

Olson

2021

Front. Cardiovasc. Med.

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Exercise based cardiac rehabilitation (CR) is recognized internationally as a class 1 clinical practice recommendation for patients with select cardiovascular diseases and heart failure with reduced ejection fraction. Over the past decade, several meta-analyses have generated debate regarding the effectiveness of exercise-based CR for reducing all-cause and cardiovascular mortality. A common theme highlighted in these meta-analyses is the heterogeneity and/or lack of detail regarding exercise prescription methodology within CR programs. Currently there is no international consensus on exercise prescription for CR, and exercise intensity recommendations vary considerably between countries from light-moderate intensity to moderate intensity to moderate-vigorous intensity. As cardiorespiratory fitness [peak oxygen uptake (VO2peak)] is a strong predictor of mortality in patients with coronary heart disease and heart failure, exercise prescription that optimizes improvement in cardiorespiratory fitness and exercise capacity is a critical consideration for the efficacy of CR programming. This review will examine the evidence for prescribing higher-intensity aerobic exercise in CR, including the role of high-intensity interval training. This discussion will highlight the beneficial physiological adaptations to pulmonary, cardiac, vascular, and skeletal muscle systems associated with moderate-vigorous exercise training in patients with coronary heart disease and heart failure. Moreover, this review will propose how varying interval exercise protocols (such as short-duration or long-duration interval training) and exercise progression models may influence central and peripheral physiological adaptations. Importantly, a key focus of this review is to provide clinically-relevant recommendations and strategies to optimize prescription of exercise intensity while maximizing safety in patients attending CR programs.

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Section: Pulmonary Adaptationsmentioning

confidence: 99%

Optimizing Outcomes in Cardiac Rehabilitation: The Importance of Exercise Intensity

Taylor

Bonikowske

Olson

2021

Front. Cardiovasc. Med.

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“…There is a growing body of evidence to show that lowering the WOB in cardiopulmonary patients, such as those with heart failure or chronic obstructive pulmonary disease, has important functional consequences. For example, several different methods to ‘unload’ the respiratory muscles (e.g., PAV, continuous positive airway pressure, inspiratory pressure support, helium–oxygen mixtures) have been shown to increase exercise tolerance (Bianchi et al., 1998 ; Eves et al., 2006 ) and perfusion to exercising limbs (Olson et al., 2010 ; Smith et al., 2020 ), attenuate locomotor muscle fatigue (Amann et al., 2010 ) and reduce sensations of breathlessness (O'Donnell et al., 1988 ; Vogiatzis et al., 2019 ). The provision of ventilatory assistance during exercise has consistent and measurable effects in both health and disease, highlighting the role that the act of breathing and the respiratory musculature itself have on the integrative nature of large muscle mass exercise.…”

Section: Discussionmentioning

confidence: 99%

The effect of proportional assist ventilation on the electrical activity of the human diaphragm during exercise

Gerson

Dominelli

Leahy

et al. 2022

Experimental Physiology

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New Findings What is the central question of this study?What is the effect of lowering the normally occurring work of breathing on the electrical activity and pressure generated by the diaphragm during submaximal exercise in healthy humans? What is the main finding and its importance?Ventilatory assist during exercise elicits a proportional lowering of both the work performed by the diaphragm and diaphragm electrical activity. These findings have implications for exercise training studies using proportional assist ventilation to reduce diaphragm work in patients with cardiopulmonary disease. Abstract We hypothesized that when a proportional assist ventilator (PAV) is applied in order to reduce the pressure generated by the diaphragm, there would be a corresponding reduction in electrical activity of the diaphragm. Healthy participants (five male and four female) completed an incremental cycle exercise test to exhaustion in order to calculate workloads for subsequent trials. On the experimental day, participants performed submaximal cycling, and three levels of assisted ventilation were applied (low, medium and high). Ventilatory parameters, pulmonary pressures and EMG of the diaphragm (EMGdi) were obtained. To compare the PAV conditions with spontaneous breathing intervals, ANOVA procedures were used, and significant effects were evaluated with a Tukey–Kramer test. Significance was set at P < 0.05. The work of breathing was not different between the lowest level of unloading and spontaneous breathing (P = 0.151) but was significantly lower during medium (25%, P = 0.02) and high (36%, P < 0.001) levels of PAV. The pressure–time product of the diaphragm (PTPdi) was lower across PAV unloading conditions (P < 0.05). The EMGdi was significantly lower in medium and high PAV conditions (P = 0.035 and P < 0.001, respectively). The mean reductions of EMGdi with PAV unloading were 14, 22 and 39%, respectively. The change in EMGdi for a given lowering of PTPdi with the PAV was significantly correlated (r = 0.61, P = 0.01). Ventilatory assist during exercise elicits a reduction in the electrical activity of the diaphragm, and there is a proportional lowering of the work of breathing. Our findings have implications for exercise training studies using assisted ventilation to reduce diaphragm work in patients with cardiopulmonary disease.

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“…An interesting method used to investigate respiratory muscle fatigue and its consequent activation of the metaboreflex in HF patients with exercise intolerance is the use of a noninvasive mechanical ventilator to reduce the inspiratory muscle load [ 52 , 53 , 54 , 55 ]. In these studies, the load reduction of these muscles increased blood flow of limbs, cardiac output, muscle oxygen absorption (VO 2 ), muscle oxygen diffusing capacity (DMO 2 ) and exercise tolerance and decreased the vascular resistance of limbs and sympathetic–adrenal system activity.…”

Section: Introductionmentioning

confidence: 99%

“…In these studies, the load reduction of these muscles increased blood flow of limbs, cardiac output, muscle oxygen absorption (VO 2 ), muscle oxygen diffusing capacity (DMO 2 ) and exercise tolerance and decreased the vascular resistance of limbs and sympathetic–adrenal system activity. Respiratory muscle metaboreflex needs the limbs’ blood flow since the discharge of the inspiratory muscles produces increased blood flow in the extremities and a reduction of blood flow in the respiratory musculature [ 52 , 53 , 54 , 55 ]. Therefore, it seems that inspiratory musculature training (IMT) could be presented as a useful therapy in order to decrease the respiratory muscle metaboreflex, which could reduce fatigue of these muscles [ 56 ].…”

Section: Introductionmentioning

confidence: 99%

Unraveling the Role of Respiratory Muscle Metaboloreceptors under Inspiratory Training in Patients with Heart Failure

Fernández-Rubio

Becerro‐de‐Bengoa‐Vallejo

Rodríguez‐Sanz

et al. 2021

IJERPH

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Exercise intolerance may be considered a hallmark in patients who suffer from heart failure (HF) syndrome. Currently, there is enough scientific evidence regarding functional and structural deterioration of skeletal musculature in these patients. It is worth noting that muscle weakness appears first in the respiratory muscles and then in the musculature of the limbs, which may be considered one of the main causes of exercise intolerance. Functional deterioration and associated atrophy of these respiratory muscles are related to an increased muscle metaboreflex leading to sympathetic–adrenal system hyperactivity and increased pulmonary ventilation. This issue contributes to increased dyspnea and/or fatigue and decreased aerobic function. Consequently, respiratory muscle weakness produces exercise limitations in these patients. In the present review, the key role that respiratory muscle metaboloreceptors play in exercise intolerance is accurately addressed in patients who suffer from HF. In conclusion, currently available scientific evidence seems to affirm that excessive metaboreflex activity of respiratory musculature under HF is the main cause of exercise intolerance and sympathetic–adrenal system hyperactivity. Inspiratory muscle training seems to be a useful personalized medicine intervention to reduce respiratory muscle metaboreflex in order to increase patients’ exercise tolerance under HF condition.

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Respiratory muscle work influences locomotor convective and diffusive oxygen transport in human heart failure during exercise

Cited by 7 publications

References 21 publications

Optimizing Outcomes in Cardiac Rehabilitation: The Importance of Exercise Intensity

Optimizing Outcomes in Cardiac Rehabilitation: The Importance of Exercise Intensity

The effect of proportional assist ventilation on the electrical activity of the human diaphragm during exercise

Unraveling the Role of Respiratory Muscle Metaboloreceptors under Inspiratory Training in Patients with Heart Failure

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