Author(s): KAJI, M., ITO, K., KUNIMATSU, N., OGOH, S., SHIBASAKI, M., Institution: NARA WOMEN'S UNIVERSITY, Country: JAPAN, Abstract-ID: 1824

INTRODUCTION:
The Cold Pressor Test (CPT) is widely used to assess sympathetic-mediated vascular responses (1). Traditionally, CPT involves immersing the hand in ice water; however, this procedure can be technically demanding and may induce severe pain, limiting its clinical applicability (2). Ice bag application provides practical advantages, by mechanically fixing the contact area, reducing discomfort related to wetness, and improving experimental reproducibility. However, it remains unclear whether it elicits hemodynamic responses comparable to the traditional immersion method. Therefore, this study aimed to compare the brachial artery blood flow and shear rate responses induced by two CPT modalities: ice water immersion and ice bag application.
METHODS:
Eleven healthy young adults (7 males, 4 females; 22 ± 3 years) participated in this study. Right radial artery blood pressure and electrocardiograms were recorded using a tonometry-based automated system. Participants completed two CPT trials in random order: 1) immersion of the left hand in ice water (WI trial), and 2) placement of the left hand between ice bags (IB trial) for 3 min. Brachial artery blood flow was evaluated using Doppler ultrasound. Flow-mediated dilation (FMD) was also assessed using a 5-min ischemic stimulus applied to the right forearm.
RESULTS:
Skin temperature of the middle finger decreased more during WI than during IB (-24.0 ± 2.2 ºC vs. -19.8 ± 3.4ºC, p < 0.05). This greater reduction in local skin temperature during WI may reflect a stronger peripheral stimulus. In contrast, the increase in mean arterial pressure was similar between trials (WI: +15.2 ± 10.9 mmHg vs. IB: +16.2 ± 8.9 mmHg). WI increased brachial artery blood velocity from 6.0 ± 4.0 cm/s to 7.5 ± 6.3 cm/s, whereas the IB produced a smaller change (5.8 ± 3.3 to 6.5 ± 3.2 cm/s). Although 9 of 11 participants exhibited an increase in blood velocity during WI, 2 demonstrated marked reductions despite substantial increases in blood pressure, indicating heterogeneous vascular responses.
CONCLUSION:
Ice water immersion elicited a greater increase in brachial artery blood velocity compared with ice bag application, despite similar pressor responses. These findings indicate that although both modalities effectively elevate arterial pressure, only immersion may produce a substantial local shear stimulus. The greater reduction in local skin temperature during immersion may contribute to differences in peripheral vascular signaling. The presence of divergent responses in a subset of participants highlights the complexity and inter-individual variability of vascular regulation during cold pressor stimulation.
REFERENCES:
(1) Victor RG, Leimbach WN Jr, Seals DR, Wallin BG, Mark AL. Effects of the cold pressor test on muscle sympathetic nerve activity in humans. Hypertension. 1987;9(5):429-436.
(2) Mitchell LA, MacDonald RA, Brodie EE. Temperature and the cold pressor test. J Pain. 2004;5(4):233-237.