Blood pressure measuring apparatus

• US 4,026,277 A
• Filed: 04/07/1975
• Issued: 05/31/1977
• Est. Priority Date: 04/12/1974
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Toda, Atsushi, Shigematsu, Koichi, Matsuoka, Yoshifumi
• Primary Examiner(s): Pinkham, Richard C.
• Assistant Examiner(s): Hum, Vance Y.
• Application Number:
  US05/565,371
• Time in Patent Office: 785 Days
• Field of Search: 128/2.05 A, 128/2.05 D, 128/2.05 G, 128/2.05 P, 128/2.05 Q, 128/2.05 R, 128/2.05 S, 128/2.05 M, 128/2 K, 235/92 EA
• US Class Current: 600/493
• CPC Class Codes: A61B 7/045 Detection of Korotkoff sounds A61B5/0225 takes precedence; measuring blood pressure A61B5/021
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

A blood pressure measuring apparatus in which an output of a microphone capable of detecting the Korotkoff sounds is directed to a first band-pass filter of 5 to 30 Hz and a second band-pass filter of 40 to 200 Hz, and the presence or absence of an output from the second band-pass filter is counted by a counter circuit, whereby the maximum blood pressure is indicated when the counter is set to one state and the minimum blood pressure is indicated when the counter is set to the other state.

Claims

1. A blood pressure measuring apparatus wherein the Korotkoff sounds are detected by a microphone in association with a pump and a cuff, and the Korotkoff sounds are utilized to indicate maximum and minimum blood pressures, said apparatus comprising:

first band-pass filter means connected to said microphone to pass frequency components of sphygmus sounds;

second band-pass filter means connected to said microphone to pass frequency components of the Korotkoff sounds;

first timer means connected to said first band-pass filter means to produce a first rectangular wave signal in response to an output signal of said first filter means, said first rectangular wave signal having a predetermined time which substantially covers a sphygmus wave duration;

second timer means connected to said second filter means and to said first timer means to produce a second rectangular wave signal in response to an output signal of said second filter means, said second rectangular wave signal having a timer width not shorter than the time width of said first rectangular wave signal;

clock signal generating means connected to said first timer means for generating a clock signal in response to a fall of each said first rectangular wave signal;

counter means connected to said second timer means and said clock signal generating means for reading the presence or absence of said second rectangular wave signal and for storing said second rectangular wave signal sequentially in accordance with said clock signal; and

event determining means connected to said counter means for determining the occurrence of the maximum and minimum blood pressure events and for producing output signals representing the occurrence of said blood pressure events, said event determining means including;

maximum blood pressure determining means coupled to said counter means for producing an output signal representing the occurrence of a maximum blood pressure event only after said counter has counted at least two successive outputs of said second timer means in synchronism with said clock signal, and

mimimum blood pressure determining means coupled to said counter means for producing an output signal representing the occurrence of a minimum blood pressure event only when said counter means has counted less than two successive outputs of said second timer means in synchronism with said clock signal and only after the occurrence of said maximum blood pressure event.

2. A blood pressure measuring apparatus according to claim 1, wherein said first band-pass filter means comprises

a filter circuit element having an input terminal to receive the output of said microphone,

a pulse generating circuit connected between said filter circuit element and said first timer means for generating a pulse signal upon activation by a rise of the sphygmus wave applied through said filter circuit element, and

a bias means including an electric charge storing circuit having an input terminal connected to said filter circuit element and having an output terminal connected to said pulse generating circuit, said bias means storing an electric charge in proportion to an amplitude of the sphygmus wave and applying a bias potential to said pulse generating circuit corresponding to the amount of electric charge stored, thereby to obtain a single square pulse from said timer irrespective of the intensity of the sphygmus wave.

3. A blood pressure measuring apparatus according to claim 1, wherein said first timer means comprises a third timer and a fourth timer connected in series, said third timer being activated simultaneously with a rise of a sphygmus wave applied through said first band-pass filter means and having an operation period of 200 to 500 m sec, said fourth timer being activated at the operation starting time of said third timer and having an operation period of 50 to 300 m sec, and wherein said operation period of said fourth timer is used as an operation period for detecting the Korotkoff sounds.

4. A blood pressure measuring apparatus according to claim 1, wherein said first band-pass filter means has a frequency range of 5 to 30 Hz, and said second band-pass filter has a frequency range of 40 to 200 Hz.

5. A blood pressure measuring apparatus according to claim 1, wherein said second timer means is further provided with a gate or a reset terminal connected to said first timer means to use the output signal thereof as a gate or a reset signal thereby to enable said second timer means to accept the output signal of said second filter means only during the existence of the output signal of said first timer means.

6. A blood pressure measuring apparatus according to claim 1, wherein said second filter means comprises third and fourth filters connected in parallel with each other, said third filter having a frequency pass band of 30 to 100 Hz to detect the Korotkoff sounds in the case of the maximum blood pressure measurement and said fourth filter having a frequency pass band of 50 to 100 Hz to detect the Korotkoff sounds in the case of the minimum blood pressure measurement.

7. A blood pressure measuring apparatus according to claim 6, further comprising:

third and fourth timers, each for forming the Korotkoff sound signal into a rectangular wave signal, respectively connected to said third and fourth filters;

wherein said event determining means further includes switching means coupled to said third and fourth timers for enabling said third timer to generate an output signal prior to determination of said maximum blood pressure event and for enabling said fourth timer to generate a further output signal after the determination of said maximum blood pressure event.

8. A blood pressure measuring apparatus according to claim 7, wherein said switching means further inhibits operation of said fourth timer prior to the determination of said maximum blood pressure event and inhibits operation of said third timer after the determination of said maximum blood pressure event.