Department of Clinical and Biomedical Sciences, University of Exeter Medical School, Exeter, United Kingdom.
National Institute of Health and Care Research Exeter Clinical Research Facility, Exeter, United Kingdom.
Am J Physiol Heart Circ Physiol. 2024 Jul 1;327(1):H268-H274. doi: 10.1152/ajpheart.00158.2024. Epub 2024 May 24.
Brachial artery flow-mediated dilation (BAFMD) is induced by hyperemic wall shear rate (WSR) following forearm ischemia. In older adults, there appears to be a reduced brachial hyperemic WSR and altered stimulus-response relationship compared with young adults. However, it is unclear if an altered forearm microvascular response to ischemia influences brachial hyperemic WSR in older adults. We determined associations between brachial hyperemic WSR and forearm skeletal muscle oxygen saturation in young and older adults. Healthy young ( = 17, 29 ± 7 yr) and older ( = 32, 65 ± 4 yr) adults participated in the study. BAFMD by a multigate spectral Doppler system and forearm skeletal muscle oxygen saturation by near-infrared spectroscopy were concurrently measured. When compared with the young, older adults showed reduced oxygen extraction kinetics (OE, 0.15 [0.12-0.17] vs. 0.09 [0.05-0.12]%s) and magnitude (So, 3,810 ± 1,420 vs. 2,723 ± 1,240%s) during ischemia, as well as oxygen resaturation kinetics (So, 2.5 ± 0.7 vs. 1.7 ± 0.7%s) upon reperfusion (all < 0.05). When OE in the young and So in older adults were stratified by their median values, young adults with OE above the median had greater hyperemic WSR parameters compared with those below the median ( < 0.05), but So in older adults did not show clear differences in hyperemic WSR parameters between those above/below the median. This study demonstrates that, in addition to a reduced microvascular response to ischemia, there may be a dissociation between microvascular response to ischemia and brachial hyperemic WSR in older adults, which may result in a further impairment of BAFMD in this cohort. Microvascular response to ischemia and subsequent reperfusion is diminished in older adults compared with the young. Furthermore, there appears to be a dissociation between the microvascular response to ischemia and brachial hyperemic WSR in older adults, which may further disturb the BAFMD process in this cohort. A reduced BAFMD in older adults may be a result of multiple alterations occurring both at macro- and microcirculation.
肱动脉血流介导扩张（BAFMD）是在前臂缺血后，通过充血时的壁切变率（WSR）诱导产生的。与年轻人相比，老年人的肱动脉充血性 WSR 似乎较低，并且刺激-反应关系也发生了改变。然而，目前尚不清楚前臂对缺血的微血管反应改变是否会影响老年人的肱动脉充血性 WSR。我们确定了年轻人和老年人的肱动脉充血性 WSR 与前臂骨骼肌氧饱和度之间的相关性。健康的年轻人（n=17，29±7 岁）和老年人（n=32，65±4 岁）参加了这项研究。通过多门光谱多普勒系统测量 BAFMD，通过近红外光谱测量前臂骨骼肌氧饱和度。与年轻人相比，老年人在缺血期间表现出较低的氧提取动力学（OE，0.15[0.12-0.17]%s 比 0.09[0.05-0.12]%s）和幅度（So，3810±1420%s 比 2723±1240%s），以及再灌注期间的氧再饱和动力学（So，2.5±0.7%s 比 1.7±0.7%s）（均<0.05）。当年轻人和老年人的 OE 根据中位数进行分层时，OE 高于中位数的年轻人的肱动脉充血性 WSR 参数比 OE 低于中位数的年轻人更大（<0.05），但老年人的 So 在中位数以上/以下的肱动脉充血性 WSR 参数之间没有明显差异。这项研究表明，除了对缺血的微血管反应降低之外，老年人的缺血反应与肱动脉充血性 WSR 之间可能存在分离，这可能导致该人群的 BAFMD 进一步受损。与年轻人相比，老年人对缺血和随后的再灌注的微血管反应减弱。此外，老年人的缺血反应与肱动脉充血性 WSR 之间似乎存在分离，这可能会进一步扰乱该人群的 BAFMD 过程。老年人的 BAFMD 降低可能是宏观和微循环中同时发生的多种改变的结果。
