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At least 37 records · Page 2Linked to original sources
PubMed1991

[Spectrum analysis of heart rate. A method of studying the role of the autonomic nervous system in the regulation of blood circulation].

Spectral analysis of heart rate variability has recently been shown to be a reliable noninvasive test for quantitative assessment of cardiovascular automatic regulatory responses. In 12 ambulant normotensive healthy young males (mean age 23 +/- 1 years) after a period of 10 min. for stabilisation, a continuous ecg recording (lead CM-5) for 8 min. was obtained in the supine and standing position, with a controlled respiration rate 15/min. Power spectrum of 512 point time series (R-R intervals) in both positions was calculated using a fast Fourier transform-based window periodogram method. Based upon results from the literature the power spectrum analysis was performed on two components: low frequency LF (0.05-0.15 Hz) and high frequency HF (0.15-0.50 Hz). Mean R-R interval decreased on standing position from 0.79 +/- 0.10 s to 0.59 +/- 0.11 s (p less than 0.001). The ratio HF/LF in supine was 0.63 +/- 0.70 and on standing position 2.54 +/- 0.73 (p less than 0.001). The relative LF component of the total HR power spectrum increased from 22.8% +/- 12.1% to 42.9 +/- 14.4% (p less than 0.001) after changing the position from supine to standing, and the relative HF component decreased from 56.3 +/- 22.4% to 25.5 +/- 16.2 (p less than 0.001). The total power was significantly lower when standing in comparison to supine position (681 +/- 519 s2, 1188 +/- 963 s2 respectively, p less than 0.05). Our results suggest that heart rate fluctuations in supine position in normal men are mainly vagally determined (HF power spectrum component).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Validity of catheter-tip Doppler technique in assessment of coronary flow velocity and application of spectrum analysis method.

Measurement of coronary flow velocity in clinical cases contributes to understanding the pathophysiology of coronary circulation. To determine absolute coronary flow velocity, coronary blood flow was assessed with an end-mounted Doppler catheter (3Fr, 20 MHz), which was combined with a custom-designed fast-Fourier transformation analysis system. In vitro study using model circuit, actual flow velocity (8 to 96 cm/s) was well correlated with that determined by this catheter system (y = 1.01 X +1.5, r = 0.988). In a clinical study of 12 patients with normal coronary arteriograms, the Doppler catheter was positioned at the proximal left anterior descending artery. Clear flow velocity patterns, which consisted of predominant diastolic components and preceding small systolic components, were obtained in all cases. The peak flow velocity was 17 +/- 8 cm/s (mean +/- standard deviation) during systole and 44 +/- 12 cm/s during diastole in this portion. In 5 patients, the great cardiac vein flow, which reflects the left anterior descending artery flow, was simultaneously measured during rapid atrial pacing. During pacing, percent increases in flow velocity were well correlated with those in great cardiac vein flow (y = 0.90 x +6.4, r = 0.935). These results indicate that catheter-tip Doppler technique with fast-Fourier transformation analysis may be useful in quantitatively determining coronary flow velocity in clinical cases.

Aged↗
PubMed1990

[Correlation function and power spectrum analysis of auditory brainstem responses (ABR)].

Correlation function and power spectrum analyses were made for ABR of 20 normal ears and 14 ears with retrocochlear lesions. Power spectrum of normal ABR had three peaks, F0, F1 and F2; their frequencies being 125, 552.5, 967.5Hz respectively; the spectrographic shapes were of good similitude. The curve of cross correlation function in normal ABR was V-shaped, with the valley at 6-8 ms delay. In ABR of the retrocochlear lesions, the peaks of power spectrogram appeared lower and smoother with F1, F2 shifting to left and varying obviously. Their curves of cross correlation function were even and had no regular pattern. We have found that, F1 and F2 shift may be a characteristic of hearing disorder and the analysis of cross correlation function could help for the detection of useful signal from distorted signals.

Auditory Diseases, Central↗