Method and apparatus for automatic blood pressure monitoring

• US 5,215,096 A
• Filed: 07/03/1991
• Issued: 06/01/1993
• Est. Priority Date: 10/26/1990
• Status: Expired due to Term

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Zapf, Christian, Frankenreiter, Michael
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): Pontius, Kevin
• Application Number:
  US07/725,182
• Time in Patent Office: 699 Days
• Field of Search: 128/672, 128/677-686
• US Class Current: 600/495
• CPC Class Codes: A61B 5/02225 using the oscillometric method
• CPC Class Codes: A61B 5/0225 the pressure being controlled by electric signals, e.g. derived from Korotkoff sounds

Abstract

A non-invasive automatic blood pressure monitor uses the oscillometric technique. That is, a cuff is inflated and then deflated in discrete deflation steps, while the oscillations caused by movement of the arterial walls are recorded during each deflation step. If no oscillations occur, the deflation step is interrupted when a predetermined time period (t_max) has expired. According to the invention, said predetermined time period (t_max) is varied according to the heart rate (step 13). This leads to considerable reduction of required time for each measurement.

Claims

1. Method for automatic non-invasive monitoring of a patient'"'"'s blood pressure, comprising the steps of:

applying a cuff (5) around a limb of the patient;

inflating said cuff (5) to a predetermined pressure;

step-wise reducing the pressure applied to said cuff (5);

holding the applied pressure constant at each step until at least one superimposed oscillation caused by a heartbeat has occurred, or until a predetermined time period (t_max) has expired, whichever occurs first;

measuring amplitudes of said superimposed oscillations and processing them in order to determine at least one of the following;

systolic, diastolic, mean blood pressure, characterized by the steps of;

determining a time interval between heart beats, of the patient; and

varying said predetermined time period (t_max) in dependence on said determined time interval, such that the duration of said predetermined time period (t_max) is increased when said time interval increases.

2. Method according to claim 1, characterized in that said predetermined time period (t_max) is substantially proportional to said time interval.

3. Method according to claim 2, characterized by adding an offset (Δ

) to said predetermined time period (t_max), said offset (Δ

) being a constant.

4. Method according to claim 2, characterized by adding an offset (Δ

) to said predetermined time period (t_max), said offset (Δ

) being a variable which depends on said time interval.

5. Method according to claim 1, characterized in that said predetermined time period (t_max) is compared with limits, and is set equal to a limit when t_max falls outside of a range between said limits.

6. Method according to claim 1, characterized in that said predetermined time period (t_max) is determined from a look-up table.

7. Apparatus for non-invasive measuring of a patient'"'"'s blood pressure comprising:

cuff inflation means,

cuff deflation means,

a pressure sensor (6),

wherein said cuff inflation means, said cuff deflation means and said pressure sensor (6) are set up for pneumatic connection with a cuff (5) for application around a patient'"'"'s limb,

control means operatively connected with said cuff inflation means, said cuff deflation means and said pressure sensor (6), said control means being set up to inflate the cuff (5) to a predetermined pressure and to step-wise reduce the applied pressure, said control means further being set up to hold the applied pressure constant at each step until at least one superimposed oscillation has been observed or until a predetermined time period (t_max) has expired, whichever occurs first,

blood pressure calculation means, including a microprocessor (2), for calculating the systolic, the diastolic or the mean blood pressure from the amplitudes of the superimposed oscillations recorded by said pressure sensor (6), characterized by;

interval measuring means for measuring the time interval between heart beats, and

time period calculation means set up to calculate said predetermined time period (t_max) in dependence on the time interval between the heart beats indicated by said interval measuring means.

8. Apparatus according to claim 7, characterized in that said time period calculation means comprises a look-up table which holds values of said predetermined time period.

9. Apparatus according to claim 7, characterized in that said interval measuring means comprises electrocardiogram recording means and peak trigger means, said electrocardiogram recording means being set up for connection with electrocardiogram electrodes.

10. Apparatus according to claim 7, characterized in that said interval measuring means comprises plethysmogram recording means and peak trigger means, said plethysmogram recording means being set up for connection with a plethysmogram transducer or an oxygen saturation transducer.

11. Apparatus according to claim 7, characterized in that said interval measuring means comprises blood pressure recording means and peak trigger means.

12. Method for automatic non-invasive monitoring of a patient'"'"'s blood pressure, comprising the steps of:

applying a cuff (5) around a limb of the patient;

inflating said cuff (5) to a predetermined pressure;

step-wise reducing the pressure applied to said cuff (5);

holding the applied pressure constant at each step until at least one superimposed oscillation caused by a heartbeat has occurred, or until a predetermined time period (t_max) has expired, whichever occurs first;

measuring amplitudes of said superimposed oscillations and processing them in order to determine at least one of the following;

systolic, diastolic, mean blood pressure, characterized by the steps of;

determining the heart rate of the patient; and

varying said predetermined time period (t_max) in dependence on the inverse of said heart rate, such that the duration of said predetermined time period (t_max) is increased when said heart rate decreases.

13. Method according to claim 12, characterized in that said predetermined time period (t_max) is substantially inversely proportional to said heart rate.

14. Method according to claim 13, characterized by adding an offset (Δ

) to said predetermined time period (t_max), said offset (Δ

) being a constant.

15. Method according to claim 13, characterized by adding an offset (Δ

) to said predetermined time period (t_max), said offset (Δ

) being a variable which depends on said heart rate.

16. Method according to claim 12, characterized in that said predetermined time period (t_max) is compared with limits, and is set equal to a limit when (t_max) falls outside of a range between said limits.

17. Method according to claim 12, characterized in that said predetermined time period (t_max) is determined via a look-up table.

18. Apparatus for non-invasive measuring of a patient'"'"'s blood pressure comprising:

cuff inflation means,

cuff deflation means,

a pressure sensor (6),

wherein said cuff inflation means, said cuff deflating means and said pressure sensor (6) are set up for pneumatic connection with a cuff (5) for application around a patient'"'"'s limb,

control means operatively connected with said cuff inflation means, said cuff deflation means and said pressure sensor (6), said control means being set up to inflate the cuff (5) to a predetermined pressure and to step-wise reduce the applied pressure, said control means further being set up to hold the applied pressure constant at each step until at least one superimposed oscillation has been observed or until a predetermined time period (t_max) has expired, whichever occurs first,

blood pressure calculation means, including a microprocessor (2), for calculating the systolic, diastolic or mean blood pressure from the amplitudes of the superimposed oscillations recorded by said pressure sensor (6) characterized by;

heart rate determination means (7),

time period calculation means set up to calculate said predetermined time period (t_max) in dependence on the heart rate indicated by said heart rate determination means (7).

19. Apparatus according to claim 18, characterized in that said time period calculation means comprises a look-up table which holds heart rate values and corresponding values of said predetermined time period (t_max).

20. Apparatus according to claim 18, characterized in that said heart rate determination means comprises electrocardiogram recording means and peak trigger means, said electrocardiogram recording means being set up for connection with electrocardiogram electrodes.

21. Apparatus according to claim 18, characterized in that said heart rate determination means comprises plethysmogram recording means and peak trigger means, said plethysmogram recording means being set up for connection with a plethysmogram transducer or an oxygen saturation transducer.

22. Apparatus according to claim 18, characterized in that said heart rate determination means comprises blood pressure recording means and peak trigger means.