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THE BURDEN OF BREATHING: HOW INCREASED WORK OF BREATHING REDUCES MUSCLE PERFUSION AND LIMITS EXERCISE TOLERANCE

Abstract

A recent series of studies have unveiled a potential link between higher work of breathing and abnormal muscle blood flow responses that contribute to exercise intolerance in patients with heart failure. These studies provide a compelling backdrop for the discussion of interwoven mechanisms that contribute to exercise intolerance and may provoke ideas beyond clinical populations. The physiological mechanisms that would be highlighted in this talk include: the work of breathing, sensory feedback, respiratory muscle blood flow, stroke volume, and leg muscle blood flow. More specifically, the proposed “big idea” is that increases in ventilation lead to elevated respiratory muscle work which limits increases in stroke volume and leg blood flow. The consequences of these responses will be discussed in the context of exercise performance. For example, although it may be straightforward to understand that limited leg muscle blood flow would limit exercise – how does this influence the sensory feedback mechanisms that might further drive increases in ventilation? Quickly, the “downward spiral” of events will be uncovered with heart failure as the primary clinical backdrop. A great deal of effort will be made to also provide context for these responses as the relate to other populations.

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