Session P82.2

Blood Pressure and Impedance Cardiography during Tilt Table Test

P Jurak*, J Halamek, V Vondra, M Plachy,
P Frana, P Leinveber

Institute of Scientific Instruments
Brno, Czech Repub.

Aim: Our aim was to evaluate and to compare changes of arterial blood pressure (BP), heart rate and thoracic impedance cardiography (TIC) parameters during tilt table test and to discuss possible diagnostic contribution.
Methods: The Protocol - subject in supine-75°tilt-supine position for 5-8-5 minutes; paced breathing 0.33 Hz during the whole measurement. We recorded ECG, BP (Finapres) and TIC (ISI BM1.2). Our data refer to 26 healthy subjects (19 men, average age 42+/-17 years, min 24, max 72 years). Within 3-minute intervals S1 (supine 1), T1 (during tilting) and S2 (supine 2) we detected and computed mean values from beat-to-beat obtained: RR intervals, systolic SBP and diastolic DBP blood pressure, pulse pressure ?BP, maximum of derivative BP dBP/dtmax, difference ?dBP = dBP/dtmax -dBP/dtmin, from TIC : difference ?Zx = Zxmax -Zxmin, maximum of derivative Zx -dZx/dtmax and difference ? dZx = -dZx/dtmax +dZx/dtmin.
Results: Values in S1=100%, T1 and S2 : RR intervals 89****, 97*; SBP 98, 99; DBP 103*, 101; ?BP 91, 95; ?Zx 86****, 95**; -dBP/dtmax 101, 98; ?dBP 95**, 96*, -dZx/dtmax 90***, 96; ?dZx 89****, 96***; * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001. Significant correlation with RR intervals within T1 interval was detected only in TIC parameters: -dZx/dtmax 0.51**; ?dZx 0.50*.
Conclusion: The results provide clear message: TIC parameters reflect supposed changes in hemodynamic system, primarily the decrease of stroke volume and the increase of heart rate. Only TIC parameters significantly correlate with changes of heart rate during tilting in individual subjects. This means that changes while tilting are not randomized and are linked with actual hemodynamic state. This cannot be claimed about BP parameters. Within healthy subjects BP does not drop dramatically while tilting, because the body compensates decrease in BP flow with an increase in heart rate and constriction of the blood vessels in the legs. Moreover, measured BP doesn’t reflect hemodynamic changes correctly and the continuously measured non-invasive photo-plethysmographic signal suffers from many problems concerning with blood circulation in finger with cuff and hydrostatic changes during tilting.

(Abstract Control Number: 184)