Blood pressure corrected evoked flow responses Methods NVC measurements were evaluated in a heterogeneous population of two sepa- rate studies consisting of 21 female subjects who had experienced preeclampsia 14, 15 Alzheimer’s disease patients, 17 subjects with mild cognitive impairment and 18 healthy elderly 9. The Institutional Review Board of the MUMC ap- proved both studies from which data is used and all subjects gave written in- formed consent. Demographics of all subjects are shown in table 1. All experi- ments were performed in a quiet room while the subjects laid down with the head slightly tilted. During the experiment the blood flow velocity in the left posterior cerebral artery (P2-segment) and the right middle cerebral artery was measured using a Multidop X4 Doppler device (DWL, Sipplingen, Germany). The two 2-Mhz Doppler probes were mounted on a head band. Continuous arterial blood pressure was recorded at the right hand index or middle finger using a non-invasive cuff device (Task Force Monitor, CN Systems, Austria). The elec- trocardiogram (ECG) was recorded to facilitate calculation of beat-to-beat ABP and CBFV. Table 1 Patient demographics Pre- Alzheimer’s Mild cogni- Healthy eclampsia disease tive impaired elderly n 21 15 17 18 Age years 29 (4) 72 (7) 70 (7) 70 (7) Male/Female 0/21 7/8 11/6 8/10 Systolic BP 123 (13) 139 (11) 133 (11) 134 (15) mmHg Diastolic BP 83 (9) 91 (8) 86 (10) 88 (12) mmHg To evoke transient cerebral blood flow changes a visual stimulation paradigm was used consisting of at least 10 repetitive episodes of 40 seconds of visual stimulation (“On”), i.e. watching a colored cartoon movie alternated with 20 seconds of black screen (“Off”). During the “Off” period the subjects were in- structed to close their eyes. The transition between phases was indicated by an audible tone. Based on ECG the software automatically detected cardiac cycles and for each beat averages were determined for cerebral blood flow velocity (mCBFV) and blood pressure (mBP). Also the systolic values sCBFV and sBP were taken for each cardiac cycle. All further data analysis was performed for both mean and 83
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