Effects of respiratory muscle unloading on leg muscle oxygenation and blood volume during high-intensity exercise in chronic heart failure

摘要

In this context, it is intuitive to consider that enhanced exercise capacity after RM unloading probably results from a better balance between local O2 demand and supply with beneficial effects on the resulting dyspnea (31, 35, 42, 54). An important contributory explanation, however, might be related to blood flow redistribution from respiratory to locomotor muscles (14, 20, 21). There are several lines of evidence suggesting that increased fatiguing contractions and accumulation of metabolites in the inspiratory and expiratory muscles may activate unmylenated type IV phrenic afferents, increasing sympathetic vasoconstrictor activity via a supraspinal reflex with the purpose to redirect blood flow from peripheral to ventilatory muscles (4, 21, 33,43, 45,48,49).