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At least 1,711 records · Page 95Linked to original sources
PubMed1987

Spectral analysis of cough sounds recorded with and without a nose clip.

The voluntary cough sounds of healthy volunteers, patients with chronic rhinitis, chronic rhinitis with bronchial asthma and asthma were recorded with and without a nose clip. A gated series of signals of the first cough sound lasting 200 ms was analysed by a system with a 20 ms delay of the first signal. In the case of filtered cough sounds, low-cut digitally, the mean values of averaged spectra of the healthy volunteers showed a first peak around 350 Hz, similar to the expiratory spectra of respiratory sounds. Second and third harmonics were also identified. The mean values of averaged spectra from the patients with airway disease differed significantly in the range of low frequency components. The upper airways work as narrow-band acoustic filters determining the harmonic contents of speech as well as those of cough sounds. To minimize these effects for acoustic analytical purposes, the application of a nose clip is suggested to find the cough harmonics related to those of pulmonary sounds. The voluntary cough sounds contain diagnostic information, but to build up a quantitative, diagnostic, decision-making system, further investigations as well as standardization of recording and analysis are necessary.

Adolescent↗
PubMed1986

Power spectral analysis of the surface electromyogram during shivering.

The purpose of this study was to describe the frequency content of the electromyogram (EMG) recorded during shivering and determine if the EMG power spectrum changed as a function of the shivering duration. Six semi-nude males were exposed to cold air (5 degrees C, 20% rh) for 80 min while quietly sitting. Rectal (Tre) and mean skin (Tsk) temperatures were recorded. Shivering of the masseter muscle was determined using bipolar surface electrodes. The EMG was amplified, recorded, and subsequently digitized at 2048 Hz. The power spectrum was calculated from eight serial 0.25s EMG samples by Fourier analysis from a frequency of 4 through 480 Hz. The eight power spectra were averaged and centroid frequency (fc) calculated. During the first 10 min of exposure, Tsk rapidly dropped from 32.6 +/- 1.6 to 26.2 +/- 1.3 degrees C, then slowly declined reaching 22.5 +/- 0.7 degrees C after 80 min. Tre rose from 37.1 +/- 0.1 to 37.4 +/- 0.1 degrees C, declining after 40 min to 37.2 +/- 0.1 degrees C. Shivering was observed within 5 min after entering the cold chamber. EMG activity after 10 min exhibited an fc of 177.2 +/- 6.2 Hz. When power was integrated over 60 Hz bandwidths, the predominant frequency band of the EMG power spectrum was 60-120 Hz. Although shivering intensity increased with time, the EMG power spectrum exhibited no significant changes. These results suggest that the EMG power spectrum during shivering did not exhibit changes characteristic of muscle fatigue or muscle cooling during the 80-min cold air exposure.

Adult↗
PubMed1985

Prospective evaluation of the accuracy of duplex scanning with spectral analysis in carotid artery disease.

Prospective evaluation of duplex scanning of the carotid vessels was performed over a 2-year period in 125 consecutive patients (249 vessels) with transient ischaemic attacks or minor stroke. Defining disease as a stenosis of greater than 15% reduction of the vessel diameter, with subgroups of 16-49% stenosis, 50-99% stenosis and occlusion, the sensitivity obtained was 96%, specificity 93% and accuracy 94%. With the use of linear multiregression analyses further subgrouping into 50-75% and 76-99% stenosis was performed. The best predictive variables were, in decreasing order, peak systolic velocity, late diastolic velocity and the difference between peak systolic and late diastolic velocity in the internal carotid artery. The additional periorbital Doppler examination caused a slight improvement in determination coefficient and diagnostic accuracy.

Adult↗