End tidal Co2 is an independent determinant of systolic blood pressure in women

Objective Recent studies have shown that high resting end tidal CO 2 (PECO 2 ) is a marker for blood pressure sensitivity to high sodium intake by normotensive humans. The present study investigated the association of resting PECO 2 with resting blood pressure in participants in the Baltimore Longitudinal Study on Aging (BLSA). Design PECO 2 of 314 healthy participants (153 men and 161 women, aged 21-79 years) was measured by a respiratory gas monitor during 25 min of seated rest, and blood pressure every 5 min by an automated oscillometric system. The independent associations of PECO 2 and other variables with systolic (SBP) and diastolic (DBP) blood pressure were analysed via multiple regression. Sex differences in age-associated changes in PECO 2 and in the role of pulmonary capacity in the PECO 2 -blood pressure relationships were also studied. Results Resting PECO 2 was an independent predictor of SBP in women (β = 0.215; P< 0.0015; overall r 2 = 0.27; P< 0.0001), and accounted for more than 10% of the variance in SBP in women over age 50 years. No such associations of PECO 2 with SBP of men, or with DBP of men or women, were observed. PECO 2 was lower in younger women (36.0 ± 0.9 mmHg) than in younger men (40.4 ± 2.0), but higher in older women (37.1 ± 0.5) than in older men (35.5 ± 0.4). Conclusions PECO 2 is an independent determinant of resting SBP in women, especially those aged 50 years or more. The origin of individual differences in resting PECO 2 and its possible role in the development of chronic hypertension remain to be clarified.