AUDIBLE BLOOD PRESSURE MONITOR

• US 3,658,060 A
• Filed: 08/19/1969
• Issued: 04/25/1972
• Est. Priority Date: 08/19/1969
• Status: Expired due to Term

• Current Assignee: Environmental Technologies Group, Inc.
• Original Assignee: Anders A. Eklof
• Inventors: Eklof, Anders A.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US04/855,072
• Time in Patent Office: 980 Days
• Field of Search: 128/2.5A,2.5D,2.5F,2.5G,2.5M,2.5P,2.5Q,2.5R,2.5T,2.6A
• US Class Current: 600/486
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/7415 Sound rendering of measured values, e.g. by pitch or volume variation A61B5/741 takes precedence

Abstract

A first train of pulses whose pulse repetition frequency and pulsewidth are proportional to blood pressure is generated. A second pulse train of constant width pulses synchronized with the first train of pulses is also generated. The pulsewidth of the pulses in each train are adjusted to be equal at some normal valve of blood pressure. The two pulse trains are then subtracted, one from the other, and the resultant signal is used to drive a loudspeaker to produce an audio signal. The pitch of the audio signal is proportional to blood pressure deviation from the normal and any rhythmic variation in pitch is proportional to heart beat rate. An alarm circuit includes a capacitor which is charged by variations in blood pressure characteristic of heat beats. In heart beat ceases the capacitor is discharged and one of the pulse trains is blocked from the subtraction circuit so that the resultant audio signal is a loud monotone signal which decays as blood pressure drops.

Claims

1. A blood pressure monitor comprising:

means for generating a first pulse train having a pulse repetition frequency proportional to blood pressure and a duty cycle related to the rate of blood pressure change;

adjustable means responsive to said first pulse train for generating a second pulse train having a pulse repetition frequency equal to the pulse repetition frequency of said first pulse train and synchronized therewith and including means for adjusting the pulsewidth of the pulses in said second pulse train, said second train pulsewidth thereafter remaining constant;

means combining said first and second pulse trains for generating an output signal; and

, utilizations means responsive to said output signal for monitoring said blood pressure.

2. A blood pressure monitor as recited in claim 1 with additionally muting means for attenuating said output signal when said output signal is below a predetermined threshold.

3. A blood pressure monitor as recited in claim 2 wherein said muting means includes means for varying said predetermined threshold.

4. A blood pressure monitor as recited in claim 1 wherein said combining means comprises means for subtracting one of said first and second pulse trains from the other of said pulse trains to produce a third pulse train comprising said output signal.

5. A blood pressure monitor as recited in claim 4 with additionally:

means integrating said third pulse train for generating a DC voltage;

threshold means responsible to said DC voltage for generating a switching signal;

a first attenuated signal path connecting said subtracting means with said utilization means; and

, a second signal path controlled by said switching signal and shunting said first path.

6. A blood pressure monitor as recited in claim 4 with additioNally:

means integrating said third pulse train for generating a DC voltage; and

, means responsive to said DC voltage for varying the response of said utilization means to said third pulse train.