| Summary: | Objective. Pressure wave reflection poses a load on the heart often augmenting pressure and adversely affecting cardiac output. Reflection effects are age dependent and may be altered by sympathetic activation by postural stress. We sought to determine the influence of standing on wave reflection and total peripheral resistance (TPR), in healthy elderly and young individuals. Wave reflection is believed to be increased by higher TPR.
Design. Analysis of aortic pressure reconstructed from noninvasive finger arterial pressure and calculated aortic flow.
Subjects. Healthy elderly (n=15) and healthy young subjects (n=15).
Interventions. At least 5minutes supine followed by 5minutes standing.
Measurements. Calculated aortic pressure and flow were used to derive forward (Pf) and backward (Pb) pressure waves, Reflection Magnitude (RM, amplitude ratio of Pb and Pf), Augmentation Index (AI), and TPR in supine position, and after 60 s and 300 s of standing.
Results. RM and AI were higher in the elderly group as expected. Upon standing, in both groups, diastolic pressure and heart rate increased while pulse pressure, stroke volume and cardiac output decreased; RM and AI decreased but TPR increased. Pb decreased in both groups, but Pf remained the same in the elderly group whereas it decreased in the young group.
Conclusions. With standing, hemodynamic variables change similarly in elderly and young healthy subjects. The opposite changes in RM and TPR during postural stress in both young and elderly suggest that wave reflections do not solely originate from the periphery.
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