Dynamics of Muscle Microcirculatory Oxygen Exchange

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Purpose:Beyond the initial cardiodynamic “Phase I,” pulmonary oxygen uptake (V̇O2) kinetics are dictated largely by, and resemble closely, the V̇O2 of the exercising muscles (V̇O2m). Within those muscles, the microcirculation is responsible for affecting almost all blood–myocyte O2 transfer, and thus, observations at this site may provide key insights into muscle oxidative function in health and dysfunction in disease.Methods:Recently, a novel combination of microscopy and phosphorescence quenching techniques has been utilized to understand the dynamics of microvascular O2 delivery (𝑄̇O2m) and muscle O2 utilization (V̇O2m) at the onset of muscle contractions.Results:These experiments have addressed longstanding questions regarding the site of control of V̇O2m kinetics and provide a first look at capillary hemodynamics at exercise onset in healthy muscle and their derangements resulting from chronic diseases such as heart failure and diabetes.Conclusion:This paper will review these novel findings within our current understanding of microcirculatory control and blood–myocyte O2 transfer.

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