Association of high resting end tidal CO₂ with carotid artery thickness in women, but not men

Background: A previous study found high resting end tidal CO₂ (PetCO₂) to be an independent determinant of systolic blood pressure in women, but not men. The present study investigates the association of PetCO₂ with the common carotid artery intima-media thickness (IMT) and wall-to-lumen (W/L) ratio in a sample of normotensive men and women. Design and methods: Resting PetCO₂ of 188 healthy volunteers, including 88 men and 100 women, in the Baltimore Longitudinal Study on Aging was monitored continuously for 25 min via a respiratory gas monitor. At another session, carotid artery IMT was determined via high-resolution B-mode carotid ultrasonography. The ratio of IMT to carotid artery diameter was calculated as W/L ratio. Resting blood pressure was determined oscillometrically every 5 min for 20 min during each session. Results: Univariate associations of PetCO₂ with systolic blood pressure (SBP) (P <001), IMT (P <001) and W/L ratio (P <001) were significant in women, but not men. Multiple regression analyses showed that high resting PetCO₂ was a predictor of SBP (P <01), IMT (P <01) and W/L ratio (P <01) in women, independent of age, body mass index and SBP. For men, age (P <001) and SBP (P <01) were independent predictors of carotid IMT, while age (P <001) was the only independent predictor of W/L ratio in men. Conclusions: This study indicates that PetCO₂ can play a role in cardiovascular structure, as well as function, in women, and that the relationship is independent of the association of PetCO₂ with blood pressure.