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Scientific Session II: Neuropediatric Ultrasound and Long‐Term Transcranial Doppler Monitoring
Author(s) -
E Michel,
S Hillebrand,
J vonTwickel,
G Jorch,
B Zernikow
Publication year - 1995
Publication title -
journal of neuroimaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.822
H-Index - 64
eISSN - 1552-6569
pISSN - 1051-2284
DOI - 10.1111/jon19955s2s69
Subject(s) - transcranial doppler , medicine , doppler ultrasound , cerebral blood flow , blood pressure , nuclear magnetic resonance , electrical impedance , cardiology , physics , quantum mechanics
The non‐linear relationship between instantaneous arterial blood pressure (BP) and cerebral blood flow velocity (CBFv) is well explained by the concept of critical closing pressure (CCP). Aim . Are there any links between cerebrovascular impedance and CCP7 Methods . In 10 preterm neonates (ga 25–32 wks; bw 685–1730 g; age 1–7 d) we Doppler traced CBFv (a. carotis int .). BP was traced simultaneously (aa. rad/umb/temp .). The time series of instantaneous CBFv and BP (sample rate was 50 Hz) were subjected to Fast Fourier Transform. Cerebrovascular impedance was calculated as the square root of the ratio of the corresponding peaks in the power spectra of BP and CBFv at zero frequency, and at heart rate (H) and harmonics (xH). Peaks with a signal/noise ratio worse than 5 db were rejected. Impedance was normalized to impedance at zero frequency (1 O ). Results . Spectral peaks could be distinguished at least up to 3H, and in some patients up to 11 H. Uniformly, the impedance between H and 3H (about 2 to 6 Hz) was 5‐fold reduced compared to 1 O