title: Active standing reduces wave reflection in the presence of increased peripheral resistance in young and old healthy individuals.
abstract: OBJECTIVE
  Pressure wave reflections are age-dependent and generally assumed to increase with increasing peripheral resistance. We sought to determine the effect of standing on wave reflection in healthy older and younger individuals and the influence of increased peripheral resistance.
  
  
  METHODS
  During supine rest and active standing, continuous finger arterial blood pressure was measured. Data obtained in the supine period and after 1 and 5 min standing were analysed. Aortic pressure and flow, calculated from finger pressure, were used to derive forward and backward pressure waves, reflection magnitude (ratio of backward and forward pressure waves), augmentation index, and peripheral resistance.
  
  
  RESULTS
  Fifteen healthy older (aged 53±7 years) and 15 healthy younger (aged 29±5 years) individuals were included. In both groups, upon standing, stroke volume, cardiac output and pulse pressure decreased with an increase in heart rate and in diastolic pressure. In the older group peripheral resistance increased from 1.3±0.4 to 1.5±0.4 and 1.5±0.4 for supine, 1 and 5 min standing, whereas reflection magnitude decreased from 0.67±0.1 to 0.61±0.1 and 0.61±0.1, and augmentation index from 33±11 to 23±12 and 25±11. In the younger group peripheral resistance increased from 0.9±0.2 to 1.1±0.2 and 1.1±0.2, whereas reflection magnitude decreased from 0.55±0.05 to 0.48±0.05 and 0.49±0.05 and augmentation index from 18±11 to 1±18 and 4±19.
  
  
  CONCLUSIONS
  With standing, haemodynamic variables change similarly in older and younger individuals. The opposite changes in reflection magnitude and peripheral resistance suggest that reflection and pressure augmentation are not solely dependent on peripheral resistance.
authors.affiliation: Department of Internal Medicine, Laboratory for Clinical Cardiovascular Physiology, Center for Heart Failure Research, University of Amsterdam, The Netherlands.
authors.forename: Shyrin C A T
authors.initials: SC
authors.lastname: Davis
authors.forename: Berend E
authors.initials: BE
authors.lastname: Westerhof
authors.forename: Bas
authors.initials: B
authors.lastname: van den Bogaard
authors.forename: Lysander W J
authors.initials: LW
authors.lastname: Bogert
authors.forename: Jasper
authors.initials: J
authors.lastname: Truijen
authors.forename: Yu-Sok
authors.initials: YS
authors.lastname: Kim
authors.forename: Nico
authors.initials: N
authors.lastname: Westerhof
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: van Lieshout
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D006801:Humans; D008875:Middle Aged; D011187:Posture; D014655:Vascular Resistance