CLINICAL STUDIES ON KOROTKOFF'S SOUND. (2) FREQUENCY ANALYSIS OF KOROTKOFF'S SOUND

Abstract

In an effort to attain a definite theory, I carried out the frequency analysis in each point of the Korotkoff sounds with the use of soundspectrograph. Spectral phonocardiography gives better frequency analysis than the ordinary phonocardiography. Materials studied are divided into 4 groups, namely, 1) 11 cases of arteriosclerosis with systolic hypertension of more than 150 mmHg, 2) 19 cases of arteriosclerosis with systolic pressure of less than 150 mmHg, 3) 5 cases of juvenile hypertension with systolic pressure of more than 1.50 mmHg, and 4) 29 cases of healthy young persons. In addition a few cases of aortic insufflciency have been studied. All studied were done at resting status in supine position and the pressure cuff was placed on the right arm in the usual manner for blood pressure measuring. Crystal microphone head was placed hermetically on the brachial artery distal to the cuff, and thus, Korotkoff sound was recorded. Korotkoff sound is recorded on a tape through the microphone and preamplifier having high pass frequency characteristics. These signals of Korotkoff sound are fed into the input terminal of the soundspectrograph from the line output terminal of the tape recorder. I was not able, judging from the wave types recorded on the oscillograph, to which point sounds they were, but on the spec-trograph they were easily distinguishable. The 1st, 3rd and 4th sounds were clear, transient sounds of short duration. The second phase sound, however, were of longer duration and could be classified as the third types. The frequency range of the tone-segment of each type was wide, comprising from a very low frequency to frequencies as high as 2000-4000 c/s. In most cases the highest frequency value was shown in the 2nd phase sounds proved to be their highest number. The murmur-segment in the 2nd phase sounds was about 1000 c/s, and it was clearly shown that the tone-segment and the murmur-segment in their principal components. A further study of the frequency distribution of the 2nd phase sounds at the time of distal hyperemia and congestion and that of 2nd phase sounds from the ordinary point to the distal showed that in the tone-segment the frequencies were nearly of equal value, while in the murmur-segment the variation of frequency distribution was clearly seen and the duration time also differed greatly. Further, the section pattern, regarding the degree of decrease, of each group of Korotkoff sound showed a gentle slope in the case of tone-segment. In the case of murmur-segment, however, the slop is less gentle, showing a high degree of decrease, and this decrease differed consider-ably with the distal condition. From the facts, I may say that in the Korotkoff sound origin there are two different mechanismus.