Introduction
The reason why we had the necessity of the objective recorded blood pressure values is as follows.
When we have introduced the blood pressure values of the inhabitants in northeast Japan to foreign country and presented the problems, we thought that our data might be doubted on the reliability of measurement values, for they were different from genarally published data. Our data showed that the blood pressurure of the inhabitants in northeast Japan had seasonally change such as low in summer and high in winter. When compared with other Japanese or western reports, our data was higher in the average of systolic blood pressure and diastolic blood pressure, and individual blood pressure values had wide distribution.1)
Blood pressure values were determined by our criteries. The certain measurement of blood pressure that we say is based on the report for the standardized from the joint research by the U.S.A. and the U.K. in 1939 and reviewd edition on standardization from American Heart assication and other examined reports in Japan.
Our measurement method was designed for the mass survey and it was the basal method of the manual of blood pressure measurement which was widly used in Japan by the examination in the Japanese Association for Cerebro-Cardiovascular Diseases Control and of the revised manual in 1979. We think that our way is one of the most reliable measurement way for the epidemiological survey.
Dr. Sasaki, one of the authors, reported at the Laboratory of Physiological Hygiene (Director;A.Keys), University of Minnesota as visting professor from 1965 to 1966, got a chance to know the international state for blood pressure measurement to attend through the countest of Dr.Stamler the First Meeting on Objective Recording of Blood Pressure which was held in Chicago 1966.
Dr.Sasaki stayed at London School of Hygiene in England on the way to Japan, there he got a chance to watch to the Sphygmomanometer for epidemiologists modified by Dr.Rose and the tape which was designed for the standardization and training of observer in blood pressure meaasurement2).
Korotkov sound was recorded by the tape recorder on the market, Dr.Rose said that there was the room for improvement at that time.
The standard of blood pressure measurement was the recognition of the point that was determined by the woman mastered in the technic for measuring of blood pressure in his laboratory. But we thoght that it was no objectivity for recognition point of blood pressure, though it was useful for education or training.
In Japan, according to the standard of the device for automated blood pressure measurement, there is no standard for blood pressure determination, though there is the standard or official examination for pressure scaler.
The Expert Committee on Examination of Automated Blood Pressure Measurement Divices(chairman:N.Sasaki) started in the Japanese Assiciation for Cerebro-Cardiovascular Disease Control, in view that there were many type of blood pressure devices which had no standard or regulation in the market.
We then invented the recording of Korotkov sound or objective recorded blood pressure values using rapidly progressing medical electronics in Japan, and reported our opinion about the difinition point of systolic blood pressure and diastolic blood pressure as the evidence of objective recorded blood pressure values at 8th World Congress of Cardiology held in Tokyo in 1974 3,4).
Method
As known well, the appearance and the disappearance of the Korotkov sounds in occulding and releasing the brachial artetries are commonly used for the indirect blood pressure measurement.
According to our studies for years, its appearance and disappearance were found to the recognition on the wave form of the microphone signal which detected above brachial artery.
We have recorded thousands of Korotkov souds with microphone and simultanous cuff pressure to data recorder, and analysing these, we defined the recognition point of Korotkov sound as follows;
1) for the systolic blood pressure
The existence of positive or negative spike which appears in the first wave of Tone-Segment, especially steepup rising spike,
2) for the diastolic blood pressure
The last wave with notch which appears in up-slope of the wave of Tone-Segment.
This system is helpful for the preservation of Korotkov sound data and have objectivety of blood pressure values, but need the great aount of recording papers (such as oscilopaper) and a recorder system, and need the observer's recognition for the definition of blood pressure values on the papers.
For the purpose of the simple and ready measurement of the blood pressure, we newly develop a portable system.
In this system the wave-form of the transducer signal are converted into digital data and stored in the memory or external casette tape.
All procedures for the blood pressure measurement are automatically controlled (including definition speed) by the built-in microcomputer analyses the digitized wave and recognizes the systolic and diastolic blood pressure according to the difinition of ours after the sampling of data.
One thousand values of systolic blood pressure and diastolic blood pressure and heart rate are stored in the memory using backup battery.
This system enables the objective recognition of the Kotokov sound. The raw wave-forms obtained from the tranceducer, which are stored in cassette tape, will be great help for the further investigations.
Outline of the systems
In the measurement the cuff is wrapped around the upper arm, and the microphone in the cuff is placed above the brachial artery.
After the cuff is inflated by the compressor, it is automatically deflated certain speed and the output of the microphone includes both both signals of the pressure puls and the Kototkov sounds.
The output signal is amplified and converted in digital form through the A/D converter, and come to the central processing unit(CPU).
The CPU checks the signal level, and if it is sufficient for the measurement, the wave-forms of the vascular sounds are analyzed to measure the blood pressure.
Otherwise another attempt may be tried automatically. The cuff pressure, the gain of the signal amplifers, etc. are readjusted by the CPU.
For the recognition of the systolic blood pressure and the diastolic blood pressure, the cuff pressure is supplied to the CPU through th A/D converter.
The heart rate and the systolic blood pressure are digitally displayed on the liquid crystal panel meters.
According to the demand, these data and information of vascular sounds(converted into digital form) can be trancemitted to the tape recorder through RS-232C interface.
The data stored in the cassette tapes can be tranceferred to the personal microcomputers on the market(such as NEC PC-9801).
Microphone
↑
Cuff →Amp→Gain controler→A/D converter→CPU→Digital display
↑↓ ↑ ↓→ RS232C → Personal Computer
Cuff inflation/deflation ↑ ↓→ Memory (Tape recorder）
↓↑ ↑
Pressure ranceducer → Amp
Fig.1. shows the block diagram of this system. This system has two processors. So if blood pressure measurement was sufficient then all data are tranceported from major to peripheral processor, and another measurement can be tried when former data are recorded to the tape recorder.
Therefore even a huge amount of data may be easily collected and sttistically analyzed.
References
1) Sasaki, N.:Epidemiological studies on hypertension in northeast Japan. In Epidemiology of Arterial Blood Pressure (eds, Kestsloot H., Joossens, J.V.) 367-377, Martinus Nijhoff, The Hague, 1980.
2)Rose, G.: Standardisation of observers in blood-pressure measurement. The Lancet 1, 673-674, 1965.
3) Sasaki, N. and Hasunuma, M.:Objective recording of blood pressure for epidemiological studies on hypertension. VIII World Congress of Cardiology, Abstract-1, p340, Sep. 19, 1978.
4) Hasunuma M. et al.:A trial for the objective recording of blood pressure information--Present status and problems of noninvasive sphygmomanometer. J. of Jpn. Assoc. Cerebro-Cardiovascular Diseases Control. 15(3), 97-107, 1981.