Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA316

Poster Communications

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

M. Tymko1, R. Stone1, T. Kersten2, K. Wildfong1, P. Ainslie1

1. Health and Exercise Sciences, University of British Columbia (Okanagan), Kelowna, British Columbia, Canada. 2. University of Radboudumc, Nijmegen, Netherlands.

The cold pressor test (CPT) elicits a transient increase in sympathetic nervous activity, minute ventilation (VE), mean arterial pressure (MAP), and common carotid artery (CCA) diameter. The extent of dilation of the CCA in response to the CPT is used as a clinical indicator of cardiovascular health status, however, the potential sex differences have yet to be explored. In response to an isocapnic (i.e. controlled CO2) CPT, we hypothesized that VE , MAP and dilation of the CCA would be reduced in females compared to males. In 20 healthy young participants (10 female and 10 male), we measured the respiratory, cardiovascular, and CCA response during an isocapnic CPT, which consisted of a three-minute right foot immersion into 0-1 degrees Celsius water. The partial pressure of end-tidal CO2 and O2 (PETCO2 and PETO2, respectively; via respiratory gas analyzer), blood pressure (via finger photoplethysmography), heart rate (via electrocardiogram), and CCA diameter and velocity (via Duplex ultrasound) were simultaneously recorded immediately prior to, and during the isocapnic CPT. During the isocapnic CPT, PETCO2 and PETO2 were controlled to baseline values using a dynamic end-tidal forcing system. The main findings during the isocapnic CPT were the following: 1) no sex differences were present in absolute or relative VE (P=0.801 and P=0.179, respectively); 2) the absolute MAP response remained unchanged between males and females (P=0.905), but the relative MAP response was reduced in females by 51% (P=0.008); and 3) the absolute CCA diameter response remained unchanged between males and females (P=0.667), but the relative CCA diameter response was reduced in females by 55% (P=0.029). Furthermore, the relative CCA diameter response was significantly correlated with the relative MAP response 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), indicating that this response was in part due to the increase in MAP during the CPT. Since the CPT is used as a clinical tool to assess cardiovascular health status, sex differences should be considered in future studies.

Where applicable, experiments conform with Society ethical requirements