Cold Pressure-mediated Vasodilation In The Brachial Artery

Flow-mediated dilation (FMD) is a well-established method for assessing vascular endothelial function. FMD refers to the vasodilation of an artery in response to increased blood flow and the associated shear stress on the endothelium. The cold pressor test (CPT) can passively increase blood flow by raising blood pressure, which, subsequently, stimulates the vascular endothelium. However, the relationship between the vascular response to CPT and endothelial function, as evaluated by FMD, remains unclear. PURPOSE: To investigate vascular responses in the brachial artery induced by cold pressure reflex and their relationship with FMD. METHODS: Nineteen normotensive subjects (16 males/ 3 females, 22 ± 3 years old) participated in a study involving a 3.5-minute CPT with the right hand immersed in cold water, and an FMD test with a 5-min ischemic stimulus applied to the right forearm. These tests were conducted in a random order. Brachial artery blood flow in the right arm was evaluated using Doppler ultrasound, and shear rate (SR) was calculated. Blood pressure was measured in the left upper arm before and at the end of each test. RESULTS: During the FMD test, hyperemia increased brachial blood flow from 8.4 ± 4.9 cm/s (range: 1.8-19.9 cm/s) to a peak of 48.4 ± 13.9 cm/s (range: 28.1-64.2 cm/s). The SR during the FMD test was 9.1 ± 5.0 [1/s] (range: 2.0-19.7 [1/s]) at rest and reached a peak of 53.8 ± 15.5 [1/s] (range: 27.3-87.2 [1/s]). The CPT increased blood pressure from a resting level of 87 ± 8 mmHg to 100 ± 12 mmHg and increased blood flow from 3.4 ± 1.9 cm/s (range: 0.8-7.4 cm/s) to a peak of 10.5 ± 6.2 cm/s (range: 3.3-30.0 cm/s). SR during the CPT was 4.6 ± 2.6 [1/s] (range: 1.5-9.2 [1/s]) at rest and 11.6 ± 6.2 [1/s] (range: 4.3-30.6 [1/s]) at peak. However, in five of 19 subjects, SR did not increase by more than two-fold from the resting level during CPT test. Furthermore, the CPT-induced SR was not correlated with either the FMD-induced SR or the increase in blood pressure during the CPT. CONCLUSION: The vasodilation observed during CPT appears to be associated with the SR component, but individual variations in sympathoexcitatory factors may play a significant role in modulating blood flow responses. Supported by: 18H03166