Blood Pressure

Blood-pressure monitoring apparatus

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Blood Pressure Abstract
A blood-pressure monitoring apparatus including a measuring device which periodically measures a blood-pressure value of a living subject at a predetermined period, and a predicting device or circuit which predicts, based on the blood-pressure values measured by the measuring device, a blood-pressure value of the living subject at a time later by a predetermined time than a time when the last one of the blood-pressure values is measured by the measuring device.

Blood Pressure Claims
What is claimed is:

1. A blood-pressure monitoring apparatus comprising:

a measuring device which periodically measures a blood-pressure value of a living subject at a predetermined period; and

predicting means for predicting, based on a plurality of blood-pressure values measured by the measuring device, a blood-pressure value of the living subject at a time later as defined by a predetermined time interval than when a last one of the plurality of blood-pressure values is measured by the measuring device.

2. An apparatus according to claim 1, wherein the predicting means comprises central-value determining means for determining, as the predicted blood-pressure value, a central value of a blood-pressure range within which the blood pressure of the living subject is predicted, based on the plurality of blood-pressure values, to fall at the later time.

3. An apparatus according to claim 1, wherein the measuring device comprises an inflatable cuff, the measuring device periodically measuring a blood-pressure value of the living subject while changing a pressing pressure of the cuff applied to a body portion of the subject.

4. An apparatus according to claim 1, further comprising period changing means for changing, when the predicted blood-pressure value does not fall within a reference blood-pressure range, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period.

5. An apparatus according to claim 1, further comprising period changing means for changing, when the predicted blood-pressure value is greater than a reference blood-pressure value, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period.

6. An apparatus according to claim 1, further comprising period changing means for changing, when the predicted blood-pressure value is smaller than a reference blood-pressure value, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period.

7. An apparatus according to claim 1, further comprising:

measured-blood-pressure-value displaying means for displaying a graph representing a time-wise trend of the plurality of blood-pressure values measured by the measuring device, on a two-dimensional coordinate system defined by a first axis indicative of a plurality of times at which the plurality of blood-pressure values are measured by the measuring device, respectively, and a second axis indicative of the plurality of blood-pressure values measured by the measuring device; and

predicted-blood-pressure-value displaying means for displaying, on the coordinate system, a graph representing the blood-pressure value predicted by the predicting means.

8. An apparatus according to claim 1, further comprising:

probability calculating means for calculating a probability with which a blood-pressure value of the living subject measured by the measuring device at the later time is equal to the predicted blood-pressure value, according to a predetermined relationship between time and probability;

probability-distribution calculating means for calculating, based on the calculated probability, a normal distribution of probability of the blood-pressure value of the living subject measured by the measuring device at the later time; and

range determining means for determining a blood-pressure range whose central value is equal to the predicted blood-pressure value and within which the blood-pressure value of the living subject measured by the measuring device at the later time falls with a predetermined probability.

9. An apparatus according to claim 8, further comprising period changing means for changing, when at least one of an upper limit value and a lower limit value of the determined blood-pressure range does not fall within a reference blood-pressure range, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period.

10. An apparatus according to claim 8, further comprising period changing means for changing, when at least one of an upper limit value and a lower limit value of the determined blood-pressure range is greater than a reference blood-pressure value, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period.

11. An apparatus according to claim 8, further comprising period changing means for changing, when at least one of an upper limit value and a lower limit value of the determined blood-pressure range is smaller than a reference blood-pressure value, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period.

12. An apparatus according to claim 8, further comprising:

predicted-blood-pressure-value displaying means for displaying, on the coordinate system, a graph representing the blood-pressure value predicted by the predicting means; and

range displaying means for displaying, on the coordinate system, a graph representing the blood-pressure range determined by the range determining means.

13. An apparatus according to claim 1, further comprising:

pulse-wave-propagation-information obtaining means for iteratively obtaining, from the living subject, a set of information relating to propagation of a pulse wave through an arterial vessel of the subject;

estimating means for iteratively estimating a blood-pressure value of the living subject, based on each set of information of the iteratively obtained sets of information, according to a predetermined relationship between pulse-wave-propagation information and blood pressure; and

predicted-blood-pressure-value modifying means for modifying, based on the estimated blood-pressure value, the blood-pressure value predicted by the predicting means.

14. An apparatus according to claim 13, further comprising:

period changing means for changing, when the predicted blood-pressure value does not fall within a reference blood-pressure range, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period; and

period re-changing means for re-changing, when the modified blood-pressure value falls within the reference blood-pressure range after the predetermined period is changed to the changed period, the changed period back to the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the predetermined period.

15. An apparatus according to claim 13, further comprising:

period changing means for changing, when the predicted blood-pressure value is greater than a reference blood-pressure value, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period; and

period re-changing means for re-changing, when the modified blood-pressure value is not greater the reference blood-pressure value after the predetermined period is changed to the changed period, the changed period back to the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the predetermined period.

16. An apparatus according to claim 13, further comprising:

period changing means for changing, when the predicted blood-pressure value is smaller than a reference blood-pressure value, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period; and

period re-changing means for re-changing, when the modified blood-pressure value is not smaller than the reference blood-pressure value after the predetermined period is changed to the changed period, the changed period back to the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the predetermined period.

17. An apparatus according to claim 13, further comprising:

18. An apparatus according to claim 17, wherein the probability calculating means comprises means for calculating a probability with which a blood-pressure value of the living subject measured by the measuring device at the later time is equal to the modified blood-pressure value, according to the predetermined relationship between time and probability, the probability-distribution calculating means comprises means for calculating, based on the calculated probability, a normal distribution of probability of the blood-pressure value of the living subject measured by the measuring device at the later time, and the range determining means comprises means for determining a modified blood-pressure range whose central value is equal to the modified blood-pressure value and within which the blood-pressure value of the living subject measured by the measuring device at the later time falls with the predetermined probability, and wherein the apparatus further comprises period changing means for changing, when at least one of an upper limit value and a lower limit value of the determined blood-pressure range does not fall within a reference blood-pressure range, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period; and period re-changing means for re-changing, when at least one of an upper limit value and a lower limit value of the modified blood-pressure range falls within the reference blood-pressure range after the predetermined period is changed to the changed period, the changed period back to the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the predetermined period.

19. An apparatus according to claim 17, wherein the probability calculating means comprises means for calculating a probability with which a blood-pressure value of the living subject measured by the measuring device at the later time is equal to the modified blood-pressure value, according to the predetermined relationship between time and probability, the probability-distribution calculating means comprises means for calculating, based on the calculated probability, a normal distribution of probability of the blood-pressure value of the living subject measured by the measuring device at the later time, and the range determining means comprises means for determining a modified blood-pressure range whose central value is equal to the modified blood-pressure value and within which the blood-pressure value of the living subject measured by the measuring device at the later time falls with the predetermined probability, and wherein the apparatus further comprises period changing means for changing, when at least one of an upper limit value and a lower limit value of the determined blood-pressure range is greater than a reference blood-pressure value, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period; and period re-changing means for re-changing, when at least one of an upper limit value and a lower limit value of the modified blood-pressure range is not greater than the reference blood-pressure value after the predetermined period is changed to the changed period, the changed period back to the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the predetermined period.

20. An apparatus according to claim 17, wherein the probability calculating means comprises means for calculating a probability with which a blood-pressure value of the living subject measured by the measuring device at the later time is equal to the modified blood-pressure value, according to the predetermined relationship between time and probability, the probability-distribution calculating means comprises means for calculating, based on the calculated probability, a normal distribution of probability of the blood-pressure value of the living subject measured by the measuring device at the later time, and the range determining means comprises means for determining a modified blood-pressure range whose central value is equal to the modified blood-pressure value and within which the blood-pressure value of the living subject measured by the measuring device at the later time falls with the predetermined probability, and wherein the apparatus further comprises period changing means for changing, when at least one of an upper limit value and a lower limit value of the determined blood-pressure range is smaller than a reference blood-pressure value, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period; and period re-changing means for re-changing, when at least one of an upper limit value and a lower limit value of the modified blood-pressure range is not smaller than the reference blood-pressure value after the predetermined period is changed to the changed period, the changed period back to the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the predetermined period.

Patent Information Search Body

Blood Pressure Description
BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a blood-pressure monitoring apparatus which monitors the blood pressure of a living subject by periodically measuring a blood-pressure value of the subject.

2. Related Art Statement

There is known a blood-pressure ("BP") monitoring device which monitors the BP of a living subject, e.g., a patient, by periodically measuring a BP value of the subject. An example of the conventional BP monitoring device is disclosed in Japanese Patent Application laid open for public inspection under Publication No. 4(1992)-261640. The BP monitoring device includes a display device which displays each of the periodically measured BP values when each BP value is measured, or a graph representing a time-wise trend or change of the periodically measured BP values.

Even a patient whose BP needs to be monitored has a constant tendency or rate of change of his or her BP, in a short period of time. That is, in a short period, a patient's BP does not change irregularly. Hence, a BP monitoring device which displays a graph representing a time-wise trend of BP values periodically measured from a patient is employed by a doctor for predicting a future BP value of the patient. Even though the last or current BP value measured from the patient may not be abnormal, if the doctor can predict from the time-wise trend of the measured BP values that the patient's BP will be abnormal in future, the doctor can immediately give necessary treatments for the patient.

However, a doctor may not be able to check each of the BP values periodically measured from of a patient. Hence, there has been proposed a BP monitoring device of a type which generates an alarm sound, when judging that a measured BP value does not fall within a predetermined normal BP range, so that the doctor may be informed of the occurrence of an abnormality to the patient. However, so long as each measured BP value falls within the normal BP range, the conventional BP monitoring device does not take any actions, even in the case where a doctor would be able to predict that the patient's BP will be abnormal in future. Therefore, there are some cases where a long time passes before the BP monitoring device generates an alarm sound, after the patient's BP indicates its abnormality. Even in the case where the doctor can check each of the periodically measured BP values of the patient, the doctor may not be able to make an appropriate judgment.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a blood-pressure monitoring apparatus which predicts a future blood-pressure value of a living subject or a future change of the blood pressure of the living subject.

The present invention provides a blood-pressure monitoring apparatus which has one or more of the technical features that are described below in respective paragraphs given parenthesized sequential numbers (1) to (20). Any technical feature which includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to that technical feature.

(1) According to a first feature of the present invention, there is provided a blood-pressure monitoring apparatus comprising a measuring device which periodically measures a blood-pressure value of a living subject at a predetermined period; and predicting means for predicting, based on a plurality of blood-pressure values measured by the measuring device, a blood-pressure value of the living subject at a later time later by a predetermined time than a time when a last one of the plurality of blood-pressure values is measured by the measuring device. The predicting means predicts, based on the blood-pressure ("BP") values measured by the measuring device, a BP value of the living subject at the later time, i.e., determines a predicted BP value of the subject that is predicted to be most probably measured by the measuring device at the later time. Therefore, the living subject such as a patient, or a medical person such as a doctor or a nurse who attends to the patient can more quickly take appropriate actions, or give appropriate treatments to the patient, in view of the predicted BP value.

(2) According to a second feature of the present invention that includes the first feature (1), the predicting means comprises a central-value determining means for determining, as the predicted blood-pressure value, a central value of a blood-pressure range within which the blood pressure of the living subject is predicted, based on the plurality of blood-pressure values, to fall at the later time. The central-value determining means may determine the central value of the blood-pressure range within which the BP of the subject is predicted to fall at the later time, by applying the method of least squares, for example, to the BP values measured by the measuring device.

(3) According to a third feature of the present invention that includes the first or second feature (1) or (2), the measuring device comprises an inflatable cuff, the measuring device periodically measuring a blood-pressure value of the living subject while changing a pressing pressure of the cuff applied to a body portion of the subject. In this case, the measuring device non-invasively measures a BP value of the subject, which leads to relieving the subject of the burden of being physically invaded for a BP measurement using, e.g., a catheter.

(4) According to a fourth feature of the present invention that includes any one of the first to third features (1) to (3), the monitoring apparatus further comprises period changing means for changing, when the predicted blood-pressure value does not fall within a reference blood-pressure range, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period. The fact that the predicted BP value does not fall within the reference BP range means that the BP of the subject will go out of the reference BP range in future. In this case, the period changing means changes the predetermined period to a changed period shorter than the predetermined period. Therefore, the measuring device will measure a BP value of the subject at the shorter period, i.e., earlier or more frequently. If the thus measured BP value does not fall within the reference BP range, the present BP monitoring apparatus may generate an alarm sound to inform the subject, or the medical person, of the occurrence of abnormality. However, the reference BP range may be replaced with a single reference BP value, according to the fifth or sixth feature (5) or (6) described below.

(5) According to a fifth feature of the present invention that includes any one of the first to third features (1) to (3), the monitoring apparatus further comprises period changing means for changing, when the predicted blood-pressure value is greater than a reference blood-pressure value, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period.

(6) According to a sixth feature of the present invention that includes any one of the first to third features (1) to (3), the monitoring apparatus further comprises period changing means for changing, when the predicted blood-pressure value is smaller than a reference blood-pressure value, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period.

(7) According to a seventh feature of the present invention that includes any one of the first to sixth features (1) to (6), the monitoring apparatus further comprises measured-blood-pressure-value displaying means for displaying a graph representing a time-wise trend of the plurality of blood-pressure values measured by the measuring device, on a two-dimensional coordinate system defined by a first axis indicative of a plurality of times at which the plurality of blood-pressure values are measured by the measuring device, respectively, and a second axis indicative of the plurality of blood-pressure values measured by the measuring device; and predicted-blood-pressure-value displaying means for displaying, on the coordinate system, a graph representing the blood-pressure value predicted by the predicting means. In this case, the graph representing the BP value predicted by the predicting means is displayed on the two-dimensional coordinate system on which the graph representing the time-wise trend of the BP values measured by the measuring device is displayed. Thus, the subject or the medical person can easily and objectively see the future change of BP of the subject, on the coordinate system.

(8) According to an eighth feature of the present invention that includes any one of the first to sixth features (1) to (6), the monitoring apparatus further comprises a probability calculating means for calculating a probability with which a blood-pressure value of the living subject measured by the measuring device at the later time is equal to the predicted blood-pressure value, according to a predetermined relationship between time and probability; probability-distribution a calculating means for calculating, based on the calculated probability, a normal distribution of probability of the blood-pressure value of the living subject measured by the measuring device at the later time; and range determining means for determining a blood-pressure range whose central value is equal to the predicted blood-pressure value and within which the blood-pressure value of the living subject measured by the measuring device at the later time falls within a predetermined probability. In this case, the range determining means determines the BP range within which the BP value of the subject measured by the measuring device at the later time falls with the predetermined probability. Therefore, the medical person can make an accurate judgment about whether or not he or she should give a quick treatment to his or her patient.

(9) According to a ninth feature of the present invention that includes the eighth feature (8), the monitoring apparatus further comprises period changing means for changing, when at least one of an upper limit value and a lower limit value of the determined blood-pressure range does not fall within a reference blood-pressure range, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period. The fact that the upper and/or lower limit value of the BP range determined by the range determining means does not fall within the reference BP range means that the BP of the subject will go out of the reference BP range in future. In this case, the period changing means changes the predetermined period to a changed period shorter than the predetermined period. Therefore, the measuring device will measure a BP value of the subject at the shorter period, i.e., earlier or more frequently. If the thus measured BP value does not fall within the reference BP range, the present BP monitoring apparatus may generate an alarm sound to inform the subject, or the medical person, of the occurrence of abnormality. However, the reference BP range may be replaced with a reference BP value, according to the tenth or eleventh feature (10) or (11) described below.

(10) According to a tenth feature of the present invention that includes the eighth feature (8), the monitoring apparatus further comprises period changing means for changing, when at least one of an upper limit value and a lower limit value of the determined blood-pressure range is greater than a reference blood-pressure value, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period.

(11) According to an eleventh feature of the present invention that includes the eighth feature (8), the monitoring apparatus further comprises period changing means for changing, when at least one of an upper limit value and a lower limit value of the determined blood-pressure range is smaller than a reference blood-pressure value, the predetermined period to a changed period shorter than the predetermined period, so that the measuring device measures a blood-pressure value of the living subject at the changed period.

(12) According to a twelfth feature of the present invention that includes any one of the eighth to eleventh features (8) to (11), the monitoring apparatus further comprises measured-blood-pressure-value displaying means for displaying a graph representing a time-wise trend of the plurality of blood-pressure values measured by the measuring device, on a two-dimensional coordinate system defined by a first axis indicative of a plurality of times at which the plurality of blood-pressure values are measured by the measuring device, respectively, and a second axis indicative of the plurality of blood-pressure values measured by the measuring device; predicted-blood-pressure-value displaying means for displaying, on the coordinate system, a graph representing the blood-pressure value predicted by the predicting means; and range displaying means for displaying, on the coordinate system, a graph representing the blood-pressure range determined by the range determining means. In this case, the graph rep