Dynamic Cerebral Autoregulation in the Old Using a Repeated Sit-Stand Maneuver

Abstract 

The aim of this study was to assess the feasibility and reproducibility of a simple and nonobtrusive repeated sit-stand maneuver to assess cerebral autoregulation (CA) in healthy old subjects >70 years. In 27 subjects aged 76 (SD 4) years, we continuously measured blood pressure using photoplethysmography and cerebral blood flow velocity in the middle cerebral artery (transcranial Doppler ultrasonography) during 5min of sitting rest and again during repeated sit-stand maneuvers at 10 s (0.05Hz) and 5 s (0.1Hz) intervals. In 11 randomly selected subjects, these measurements were repeated after 3 months. Both maneuvers induced substantial periodic oscillations in pressure and flow. For example, the maneuvers at 0.05Hz increased the power spectral density (magnitude) of blood pressure and cerebral blood flow velocity oscillations with 16.3 (mm Hg)² and 14.5 (cm/s)², respectively (p<0.001). These larger oscillations led to an increase in transfer function coherence compared with spontaneous oscillations from 0.46 to 0.60 for 0.05Hz maneuvers and from 0.56 to 0.76 for 0.1Hz maneuvers (p<0.01), allowing for more confident assessment of CA through transfer function phase and gain. This increased coherence was not associated with improved reproducibility however. In conclusion, we were able to investigate CA in old patients using these repeated sit-stand maneuvers, which, compared with spontaneous oscillations, produced a stronger and more clinically relevant hemodynamic challenge for CA. (E-mail: j.claassen@ger.umcn.nl)

Key Words: Aged, Aged, 80 and over, Ultrasonography, Doppler, Transcranial, Cerebrovascular circulation, Hemodynamics, Spectral analysis