Sex differences in the circulatory responses to an isocapnic cold pressor test

New Findings

What is the central question of this study?

To determine whether sex differences exist in the cardiorespiratory responses to an isocapnic cold pressor test (CPT).

What is the main finding and its importance?

During the CPT, there were no sex differences in the respiratory response; however, females demonstrated a reduced mean arterial pressure and reduced dilation of the common carotid artery. Since the CPT is predictive of future cardiovascular events, these data have clinical implications for improving the utility of the CPT to determine cardiovascular health risk. Sex differences should be taken into consideration when conducting and interpreting a CPT.

Abstract

The cold pressor test (CPT) elicits a transient increase in sympathetic nervous activity, minute ventilation (V_E), mean arterial pressure (MAP), and common carotid artery (CCA) diameter in healthy individuals. Although the extent of dilation of the CCA in response to the CPT has been used as a clinical indicator of cardiovascular health status, the potential sex differences have yet to be explored. In response to a CPT, we hypothesized that elevations in V_E, MAP and dilation of the CCA would be attenuated in females compared to males. In 20 young healthy participants (10 females), we measured the respiratory, cardiovascular, and CCA responses during a CPT, which consisted of a three‐minute right foot immersion into 0–1 °C water. Blood pressure (via finger photo plethysmography), heart rate (via electrocardiogram), and CCA diameter and velocity (via Duplex ultrasound) were simultaneously recorded immediately before and during the CPT. During the CPT, while controlling end‐tidal gases to baseline values, the main findings were: 1) no sex differences were present in absolute or relative changes in V_E (P = 0.801 and P = 0.179, respectively); 2) the relative MAP and CCA diameter response were reduced in females by 51% and 55%, respectively (P = 0.008 and P = 0.029 vs. males, respectively); and 3) the relative MAP responses was positively correlated to the dilation of the CCA in males (r = 0.42, P = 0.019), females (r = 0.43, P = 0.019), and in males and females combined (r = 0.55, P < 0.001). Since the CPT is used as a clinical tool to assess cardiovascular health status, sex differences should be considered in future studies.

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