Method and apparatus for a non-invasive examination of blood circulation in a living organism

• US 5,048,533 A
• Filed: 08/30/1989
• Issued: 09/17/1991
• Est. Priority Date: 08/31/1988
• Status: Expired due to Term

• Current Assignee: Nicolay GmbH
• Original Assignee: Nicolay GmbH
• Inventors: Muz, Edwin
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): Pfaffle, K. M.
• Application Number:
  US07/400,719
• Time in Patent Office: 748 Days
• Field of Search: 128/679, 128/680-683, 128/687
• US Class Current: 600/492
• CPC Class Codes: A61B 5/02255 the pressure being controlled by plethysmographic signals, e.g. derived from optical sensors

Abstract

A method and apparatus for the non-invasive examination of the blood circulation of a living organism uses a device having: a pair of sensors (18, 19), each of which detects the value β (t) of a measurement value that changes during one pulse wave with the blood pressure of the organism and thereby with time, and transmits this value through signals; a pair of pressure sleeves for connecting the sensors with tissue of the organism through which arterial blood flows; and an electrical unit (21) for evaluating the signals of the mentioned sensors. The method includes setting two subdiastolic pressures which differ from each other by a small value in the two sleeves, transmitting signals obtained from the two sensors (18, 19) to the evaluating unit (21), and determining a circulatory function of the organism from transmitted signals in the evaluating unit.

Claims

1. A method for non-invasive determination of the actual blood pressure P_M (t) of a living organism as a function of time,

which blood pressure changes in a range comprising a diastolic and a systolic pressure, at locations of said organism which contain arteries which change their volumes dependent on said actual blood pressure and on a transmural pressure caused by said arteries;

by an apparatus which comprises;

first and second pad means, each for applying a pressure P_M1 and P_M2, respectively, to a first and a second of said locations of said organism and each having a chamber with a volume for a pressure means for producing said pressure P_M1 and P_M2, respectively,

first and second control means for said first and second pad means for setting said pressures P_M1 and P_M2, respectively, independently from each other in each of said pad means,

first and second sensor means for each of said first and second pad means, respectively, which sensor means respond to perceivable values β

₁ (t) and β

₂ (t), respectively, that change depending on said actual blood pressure and said transmural pressure and transmit signals which correspond to said values β

₁ (t) and β

₂ (t) and

an evaluating means for evaluating said signals of said sensor means,

said method comprising the steps of;

a) determining a blood pressure value of said organism which is dependent of said transmural pressure,

b) applying said first and second pad means to said first and second locations of said organisms, the arteries of said first and said second locations being parallel to each other within said organism, in order to simultaneously perceive said values β

₁ (t) and β

₂ (t) in said first and second locations independently from each other,

c) setting equal said pressures P_M1 and P_M2 applied by said first and said second pad means at each of said first and said second locations and adjusting said evaluating means for an output of equal said perceivable values β

₁ (t) and β

₂ (t) derived from said signals transmitted by said first and second sensor means,

d) setting first and second predetermined pressures as said pressures P_M1 and P_M2 at each of said first and said second locations, said first and said second predetermined pressures being smaller than said diastolic pressure of said organism and differing from each other by a value Delta P_M which is small compared with said diastolic pressure and actuating said first and said second sensor means for responding to said perceivable values β

₁ (t) and β

₂ (t), respectively, and for transmitting signals which correspond to said values, and

evaluating said transmitted signals from said sensor means received by said evaluating means for determining the blood pressure of said organism as a function of time.

2. The method according to claim 1, comprising the steps of implementing in said evaluating means an algorithm by which the differential quotient of the blood pressure is determined as a function of time according to the formula:

space="preserve" listing-type="equation">dp.sub.B1 (t)/dt=Delta P.sub.M +dβ

.sub.1 (t)/dt;

<

β

.sub.2 (t)-β

.sub.1 (t)>

evaluating said differential quotient of said actual blood pressure from said signals; and

integrating said differential quotient in order to determine the actual blood pressure P_B1 as a function of time.

3. The method according to claim 2, where said predetermined pressure P_M1 and P_M2 of said first and said second pad means, respectively, results in actual pad pressure which change dependent on said change of said volume of said arteries, comprising the steps of

taking said actual pad pressures as said perceivable values β

₁ (t) and β

₂ (t).

4. The method according to claim 2, comprising the steps of taking the radiation permeabilities of said locations as said perceivable values β

₁ (t) and β

₂ (t).

5. The method according to claim 4, comprising:

a) determining said radiation permeabilities in each of said pad means using an optoelectronic system including a radiation transmitter and a radiation sensor; and

b) using the photoelectric current flowing in the radiation sensor as said perceivable values.

6. The method according to claim 5, further comprising:

simultaneously determining the oxygen content of the blood using an additional optoelectronic system in one of said pad means, said additional system being operated with radiation of a wavelength different from the wavelength at which said optoelectronic system determining the radiation permeabilities is operated.

7. The method according to claim 1, wherein said predetermined pressures P_M1 and P_M2 are set in the range from 10 to 40 mmHg when used on children, and are set in the range from 20 to 60 mmHg when used on adults, and said value Delta P_M is set in both cases in the range from 2 to 15 mmHg.

8. Apparatus for non-invasive determination of the actual blood pressure of a living organism as a function of time, comprising:

first and second pad means for applying predetermined pressures P_M1 and P_M2 to first and second locations of said organism, respectively, which locations contain arteries which change their volume depending on said actual blood pressure and a transmural pressure caused by said arteries,

first and second sensor means for each of said first and second pad means for transmitting first and second signals corresponding to perceivable values β

₁ (t) and β

₂ (t), respectively, which values change dependent on said actual blood pressure and said transmural pressure,

means for evaluating said signals comprising computer means for implementing an algorithm

connecting means connecting said first and said second sensor means to said evaluating means for transmitting said signals to said evaluating means, wherein in said computer means said algorithm is implemented by which the differential quotient of the blood pressure is determined as a function of time according to the formula;

space="preserve" listing-type="equation">dp.sub.B1 (t)/dt=Delta P.sub.M *dβ

.sub.1 (t)/dt;

<

β

.sub.2 (t)-β

.sub.1 (t)>

so that said differential quotient is computed as a function of time from said signals received from said sensor means in said computer means which is adapted to integrate said differential quotient to determine the actual blood pressure P_M (t) as a function of time.

9. The apparatus according to claim 8, wherein said first and said second sensor means each comprises an optoelectronic system with a transmitter and a receiver for a radiation which is partly absorbed in said first and said second locations of said organism dependent on said volume of said arteries, so that said partial absorptions in said first and said second locations form said perceivable values β

₁ (t) and β

₂ (t), respectively.

10. The apparatus according to claim 9, in which one of said first or second pad means includes;

an additional sensor means comprising an additional optoelectronic system with an additional transmitter and receiver for an additional radiation which is different from said radiation of said first and second sensor means, so that said additional sensor means emits an additional signal caused by a partial absorption of said additional radiation; and

an electrical unit to determine a feature of the blood from both said additional signal and said first or said second signal of said sensor means which is included in the same of said first or second pad means, respectively.

11. The apparatus according to claim 10, wherein said first and said second pad means are formed as caps for placing them on the ends of two similar but distinct adjacent extremities of said living organism,

said two pad means being connected to each other to form a pad means unit.

12. The apparatus according to claim 9, wherein said first and said second pad means are formed as caps for placing them on the ends of two similar but distinct adjacent extremities of said living organism,

said two pad means being connected to each other to form a pad means unit.

13. The apparatus according to claim 8, wherein said first and said second pad means are formed as caps for placing them on the ends of two similar but distinct adjacent extremities of said living organism,

said two pad means being connected to each other to form a pad means unit.