Medicine and science in sports and exercise
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Med Sci Sports Exerc · Sep 1994
ReviewPerception of breathlessness during exercise in patients with respiratory disease.
The perception of breathlessness during physical activities is a frequent and disturbing complaint for patients with chronic respiratory disease. Psychophysical principles can be applied to quantitate the severity of dyspnea during cardiopulmonary exercise testing. ⋯ Studies demonstrate that the slope and/or intercept of the power production-breathlessness relationship provide a valid, reliable, and responsive approach for measurement. Ratings of dyspnea during exercise are useful to determine the severity of breathing difficulty and to assess the efficacy of therapy.
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Acute altitude illnesses include acute mountain sickness (AMS), a benign condition involving headache, nausea, vomiting, irritability, insomnia, dizziness, lethargy, and peripheral edema, and potentially lethal high-altitude cerebral edema and pulmonary edema (HAPE). Recent evidence is summarized that AMS is related to cerebral edema secondary at least in part to hypoxic cerebral vasodilation and elevated cerebral capillary hydrostatic pressure. ⋯ The adrenergic responses are likely modulated by striking increases of aldosterone, vasopressin and atrial natriuretic peptide. The effects of exercise on altitude-induced illness and various therapeutic regimens (acetazolamide, CO2 breathing, dexamethasone, and alpha adrenergic inhibitors) are discussed in light of this hypothesis.
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Med Sci Sports Exerc · Oct 1993
Inspiratory muscle performance relative to the ventilatory threshold in healthy subjects.
Inspiratory muscle performance, ventilation, and gas exchange were studied during exercise in healthy subjects to look for typical changes of pattern of contraction at the ventilatory threshold (VT). The steepening of the slope of carbon dioxide output (VCO2) vs oxygen uptake (VO2) at the VT was accompanied by a nonlinear increase of the mean rate of esophageal pressure development (Pes/TI) vs the esophageal pressure time index (PTIes) reflecting both the relative force (Pbreath/Pesmax) and duration (TI/TTOT) required for inspiration. ⋯ Inspiratory muscle performance during exercise should link the increased metabolic rate to ventilatory output. We conclude that 1) there exists an inspiratory muscle threshold that is well correlated to commonly used gas exchange thresholds, and 2) the efficiency of ventilation and gas exchange during exercise could be linked to pressure and timing of inspiratory muscle contraction.