Apparatus and method for measurement and control of blood pressure

• US 4,425,920 A
• Filed: 10/24/1980
• Issued: 01/17/1984
• Est. Priority Date: 10/24/1980
• Status: Expired due to Term

• Current Assignee: Purdue Research Foundation (Purdue University)
• Original Assignee: Purdue Research Foundation (Purdue University)
• Inventors: Geddes, Leslie A., Tacker, Willis A. Jr., Babbs, Charles F., Bourland, Joe D.
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Sykes, Angela D.
• Application Number:
  US06/200,570
• Time in Patent Office: 1,180 Days
• Field of Search: 128/672-675, 128/214 E, 128/213 R, 128/DIG. 12, 128/13, 128/640, 128/642, 128/679-680, 128/687-690, 128/691-693
• US Class Current: 600/485
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves

Abstract

Apparatus and method for measurement and control of blood pressure are disclosed. Blood pressure is indirectly continually monitored without use of a pressure transducer by sensing the pulse transit time to different sites in an artery, which transit time is inversely related to blood pressure, and developing pulses therefrom which are utilized to form arterial pulse waves, the comparison between which provide an indication of measured blood pressure. This indication is used to control blood pressure by controlling automatic release of a suitable drug into the body in amounts and over a time period as needed. The unit for measuring blood pressure includes two sets of electrodes positioned adjacent to but outside an artery at two sites (with the electrodes implanted or outside the body). Each electrode set is connected with an alternating current generator to supply alternating current at a low level to the electrodes and with demodulators to produce pulses due to a change of impedance offered to the supplied alternating current at each site. Each demodulator is connected with a detector to sense pulse arrival, and the detectors are connected with a time-interval measuring circuit. The system for control of blood pressure includes a blood pressure measuring unit that is connected with an electronic processing unit which controls a drug dispensing unit implanted in the body or attached outside the body.

Claims

1. An apparatus for measuring blood pressure, said apparatus comprising:

a pair of electrode sets for positioning adjacent to and outside an artery;

alternating current generator means for providing alternating current to each of said electrode sets;

first and second demodulator means each of which is connected with a different one of said electrode sets for forming pulses in response to receipt of signals from said electrode sets due to the impedance offered to said alternating current between the electrodes of said electrode sets to thereby determine the pulse transit time of blood flowing through said artery;

first and second detector means each of which is connected with a different one of said first and second demodulator means to indicate the time of arrival of pulses from said demodulator means and form therefrom arterial pulse waves; and

time interval measuring means connected with said first and second detector means for receiving said arterial pulse waves therefrom and responsive thereto providing an electrical signal output that is indicative of blood pressure sensed in said artery.

2. A method for measuring blood pressure in a body, said method comprising:

positioning sets of electrodes along and outside an artery having blood flowing therethrough;

applying an alternating current to said electrodes;

determining the pulse transit times between said electrodes of each of said sets of electrodes by separately demodulating the sensed impedance offered to said alternating current between the electrodes of each said set of electrodes and producing therefrom representations of arterial pulses;

separately detecting the arterial pulses to form arterial pulse waves; and

comparing the arterial pulse waves to provide therefrom a signal indicative of the pressure of said blood flowing through said artery.

3. The method of claim 2 wherein said impedance between each said set of electrodes is determined at different frequencies.