Body Size Predicts Cardiac and Vascular Resistance Effects on Men's and Women's Blood Pressure

Abstract

Key Points Summary We report how blood pressure, cardiac output and vascular resistance are related to height, weight, body surface area (BSA), and body mass index (BMI) in healthy young adults at supine rest and standing.Much inter-subject variability in young adult's blood pressure, currently attributed to health status, may actually result from inter-individual body size differences.Each cardiovascular variable is linearly related to height, weight and/or BSA (more than to BMI).When supine, cardiac output is positively related, while vascular resistance is negatively related, to body size. Upon standing, the change in vascular resistance is positively related to size.The height/weight relationships of cardiac output and vascular resistance to body size are responsible for blood pressure relationships to body size.These basic components of blood pressure could help distinguish normal from abnormal blood pressures in young adults by providing a more effective scaling mechanism. Introduction: Effects of body size on inter-subject blood pressure (BP) variability are not well established in adults. We hypothesized that relationships linking stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR) with body size would account for a significant fraction of inter-subject BP variability. Methods: Thirty-four young, healthy adults (19 men, 15 women) participated in 38 stand tests during which brachial artery BP, heart rate, SV, CO, TPR, and indexes of body size were measured/calculated. Results: Steady state diastolic arterial BP was not significantly correlated with any index of body size when subjects were supine. However, upon standing, the more the subject weighed, or the taller s/he was, the greater the increase in diastolic pressure. Systolic pressure strongly correlated with body weight and height both supine and standing. Diastolic and systolic BP were more strongly related to height, weight and body surface area than to body mass index. When supine: lack of correlation between diastolic pressure and body size, resulted from the combination of positive SV correlation and negative TPR correlation with body size. The positive systolic pressure vs. body size relationship resulted from a positive SV vs. height relationship. In response to standing: the positive diastolic blood pressure vs. body size relationship resulted from the standing-induced, positive increase in TPR vs. body size relationship. The relationships between body weight or height with SV and TPR contribute new insight into mechanisms of BP regulation that may aid in the prediction of health in young adults by providing a more effective way to scale BP with body size.

Keywords: blood pressure; body size; cardiac output; orthostatic; stroke volume; total peripheral resistance.

Figure 1

Diastolic blood pressure (DBP) plotted as a function of body weight for young men (circles) and women (crosses) at supine rest (A), regression is shown for pooled data. During minutes 7–10 of standing (B), regression of men's DBP on weight is shown with a solid line and women's with a dashed line. See Tables 2, 3 for statistically significant effects.

Figure 2

Change of diastolic blood pressure (DBP) from supine, vs. body weight (A) and height (B) for men (circles) and women (crosses). See Tables 2, 3 for statistically significant effects.

Figure 3

Systolic blood pressure (SBP) shown as a function of body weight for young men (circles, solid line) and women (crosses, dashed line) during minutes 7–10 of supine rest (A) and standing (B). See Tables 2, 3 for statistically significant effects.

Figure 4

Marginal effects plot of supine stroke volume (SV, A) vs. height for young men (circles, solid line) and women (crosses, dashed line). Change from supine (B) vs. height for young men (circles) and women (crosses). See Tables 2, 3 for statistically significant effects.

Figure 5

(A) Marginal effects plot of supine total peripheral resistance (TPR) plotted as a function of height for men (circles, solid line) and women (crosses, dashed line). (B) TPR change from supine for men and women shown as boxplots. The horizontal line in the rectangle shows the median. The central rectangle spans the interquartile range. The whiskers represent minimum and maximum values. The single data points on both the men's and women's plots, indicate outliers.

Figure 6

Regression of subject height on weight for 22 men (circles) and 16 women (crosses). Regression line is for the group of men and women combined.