末梢脈波伝播時間の自動読み取り装置 ―問題点および装置の改良に関るす一試み―
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概要
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The purpose of the present study was to develop an automated measuring instrument of peripheral pulse transit time (PTT) as an attempt to resolve the problems, which occur when the peripheral pulse wave (PW) is detected by a fixed trigger level. An important innovation for the present instrument was the decision to employ a variable trigger level (Vt), beat by beat, with evaluation of the two troublesome phenomena seen frequently in peripheral PW. Using the peak hold circuit, the fluctuation of the base line was evaluated as the negative peak amplitude (NPA), and the variation of the pulse amplitude as the peak-to-peak amplitude (PPA). Vt was then electrically decided by evaluating an equation; Vt = NPA + (n/10) × PPA. Here the number n, present by a PW trigger switch (n = 1, 2, …, 10), decided the slice rate at which the ascending limb of PW was detected, and the distorting effects clue to the conduction of PW were decreased when the presetting of n was rather small. Accomplishing this innovation, however, required that the PW he monitored as well and that it be memorized until the decision on Vt had been made. A bucket brigade device (BBD), a recently developed analogue delay unit, was composed of 4096 condenser-switch pairs and conducted the PW input in such a manner that the clock pulse controlled the switch on-off and, therefore, the timing of signal delivery between 2 adjacent condensers. The PW could be delayed from 205 msec to 512 msec by adjusting the clock cycle beforehand, with this adjustment being necessary to overcome the individual difference in peripheral PW. Thus the start signal of the PTT measurement was given by detecting the delayed ECG (generated by another BBD) at a fixed preset trigger level and the stop signal was given by detecting the simultaneously delayed PW at a variable trigger level Vt in each cardiac cycle. These 2 signals became the final outputs of the instrument, and the PTT could be measured by using a universal counter. A preliminary experiment demonstrated that the fixed trigger method that had been customarily used resulted in a more highly susceptible PTT to the troublesome phenomena mentioned above than the variable trigger method produced in the present instrument. Altogether, it was concluded that the instrument developed in the present study had a potential for continuous tracking of peripheral PTT beat by beat without these problems.
- 札幌医科大学の論文
- 1980-06-01
札幌医科大学 | 論文
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