Systemic arterial blood pressure regulation during hyperoxic CO2 rebreathing in young females and males.

The effect of biological sex on arterial blood pressure regulation during progressive hypercapnia is not well understood. The current study tested the hypothesis that arterial blood pressure responses to progressive hypercapnia would be similar between males and females. Sixteen young females and 16 age-matched males underwent a modified Duffin CO2 rebreathing protocol. Arterial blood pressure parameters (systolic [SBP], diastolic [DBP], mean arterial [MAP], pulse [PP] pressures) were acquired by manual auscultation of the brachial artery. Heart rate (HR) was determined via single-lead electrocardiography. Expired gas analysis was used to determine the partial pressure of end-tidal CO2 (PETCO2) and minute ventilation. Linear mixed-effects regression modeling was used to determine sex-by-PETCO2 interactions for key variables throughout rebreathing. At rest and throughout CO2 rebreathing, HR, MAP and DBP were not different between groups (all p > 0.05), while ventilation, SBP and PP were lower in females (all p < 0.05). No main sex-by-PETCO2 interactions were observed for any variable during CO2 rebreathing (all p > 0.05). The slope of rise in blood pressure (relative to CO2) was not significantly associated with the ventilation/CO2 slope, regardless of sex. Our findings suggest that blood pressure regulation during progressive hypercapnia is similar between the sexes, and that the variability in cardiovascular responses to hypercapnia are not linked with ventilatory responses.