Quantification of Dynamic Changes of Hemodynamic and Metabolic Responses to Brachial Artery Occlusion: A Broadband Near-Infrared Spectroscopy Study

Abstract

Cardiovascular disease (CVD) is a leading cause of death in the United States, and non-Hispanic African Americans are at higher risk than other racial and ethnic groups. Endothelial dysfunction is a major contributor to CVD development and progression. Remote ischemic pre/conditioning (RIC), which involves exposing cells or tissues to brief sublethal stress, has been shown to protect cardiovascular cells from ischemia and reperfusion injury, including CVD. This study aimed to investigate hemodynamic and metabolic dynamics in response to 5-min forearm arterial occlusion using broadband near-infrared spectroscopy. My thesis is a tripartite investigation that weaves RIC, mitochondrial dynamics, and health disparities together. Specifically, 17 The participants were instructed to lay down and follow a brachial artery occlusion protocol in the upper arm. A broadband spectrometer was then placed on the brachioradialis muscle below the cuff, proximal to the wrist. The measurement protocol consisted of a 5-min rest, 5-min arm cuff under 220 torr, and 3-min recovery. After the data processing, several key results were obtained. (1) Dynamic alterations in oxygenated and deoxygenated hemoglobin (D[HbO] and D[HHb]) showed well-known, expected patterns in response to a 5-min RIC. (2) Dynamic alterations of oxidized cytochrome c oxidase ([CCO]) exhibited a rapid increase, followed by a stationary amplitude across the 5-min RIC. (3) The wavelet transform coherence analysis enabled us to determine vascular and mitochondrial coupling and demonstrated decoupling and recoupling phases during the occlusion and recovery periods. Finally, (4) possible disparities in hemodynamic and metabolic dynamics and their coupling exist during and after the occlusion, revealing the nuanced differences between African American and Caucasian populations.