Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2002-02-12
2004-05-25
Hindenburg, Max F. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S481000, C600S561000
Reexamination Certificate
active
06740044
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a blood-pressure monitoring apparatus for use in dialysis that continuously monitors change of blood pressure of a patient during a dialysis treatment, and to a dialyzing apparatus including the blood-pressure monitoring apparatus.
2. Related Art Statement
Since blood pressure of a patient who is undergoing a dialysis treatment may largely lower, there is a need to monitor the blood pressure. A blood-pressure measuring method using a cuff is preferable with respect to reliability. However, when the cuff is used to measure the blood pressure, it is needed to increase a pressure in the cuff up to a value higher than a systolic blood pressure of the patient. Thus, the patient feels discomfort, and accordingly blood-pressure measuring operations each using the cuff cannot be carried out so frequently.
Hence, there has been proposed a blood-pressure monitoring apparatus which successively obtains a piece of blood-pressure-related information that is related to blood pressure of a patient, successively determines an estimated blood pressure of the patient based each piece of blood-pressure-related information, and monitors, based on change of each estimated blood pressure, blood pressure of the patient who is undergoing a dialysis treatment. This blood-pressure monitoring apparatus is disclosed in, e.g., Japanese patent document No. 10-043147 or its corresponding U.S. Pat. No. 5,752,920. The monitoring apparatus iteratively determines an estimated blood pressure based on a pulse-wave propagation velocity at which a pulse wave propagates in patient's body. If change of the estimated blood pressure is greater than a prescribed threshold value, indicating that patient's blood pressure may be abnormal, then the monitoring apparatus carries out a blood-pressure measuring operation using a cuff to obtain a more reliable blood-pressure value of the patient.
During a dialysis treatment, blood pressure of a patient that is clinically normal may lower little by little as time elapses. Therefore, it is a conventional practice that when the above-indicated blood-pressure monitoring apparatus is used to monitor blood pressure of a patient during a dialysis treatment, a considerably great threshold value is employed in judging whether change of each estimated blood-pressure value is abnormal, so that a normal time-wise blood-pressure decrease may not be judged as abnormal. However, if the threshold value is too great, the monitoring apparatus cannot quickly find an abnormal blood-pressure decrease.
Thus, it is desirable that the above-indicated threshold value be as small as possible so long as the threshold value does not allow a normal blood-pressure decrease to be judged as abnormal. However, a normal amount of decreasing of blood pressure during a dialysis treatment depends on each individual patient, and an abnormal blood-pressure decreasing amount that needs an emergency treatment also depends on each patient. Thus, the conventional blood-pressure monitoring apparatus has the problems that a normal blood-pressure decrease for a patient may be judged as abnormal and that an abnormal blood-pressure decrease for another patient may not be quickly found. If the abnormal blood-pressure decrease is not quickly found, then the patient may loose his or her life. Therefore, there is a tendency that the threshold value is set at a considerably small value. Thus, normal blood-pressure decreases for a patient may be frequently judged as abnormal, and blood-pressure measuring operations each using a cuff may be carried out on the patient. That is, the patient may be forced to feel unnecessary discomfort.
Meanwhile, a conventional dialyzing apparatus is used such that when the blood-pressure monitoring apparatus generates an alarm sound indicative of the abnormal blood-pressure decrease, a doctor or a nurse hurries to lower a speed of operation of the dialyzing apparatus or temporarily stop the operation of the same. Thus, a considerably long time is taken to conduct an appropriate action to treat the abnormal blood-pressure decrease.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a blood-pressure monitoring apparatus for use in dialysis that can quickly find an abnormal decrease of blood pressure of a patient without erroneously judging a normal blood-pressure decrease as being abnormal, and provide a dialyzing apparatus which can enable, when the abnormal blood-pressure decrease is found, the blood pressure of the patient to be quickly recovered.
The Inventor has carried out extensive studies to achieve the above-indicated objects, and found the facts that although a pattern of change of blood pressure during a dialysis treatment depends on each individual patient, blood pressure of each patient follows a substantially same pattern during each dialysis treatment and that the blood pressure of each patient tends to abnormally lower during only a particular period or periods within an entire duration of each dialysis treatment. Therefore, if a tight threshold value is used to find a blood-pressure abnormality during the particular period of each dialysis treatment, an abnormal blood-pressure decrease can be quickly found and, if a loose threshold value is used to find an abnormality during the remaining periods of each dialysis treatment, a normal blood-pressure decrease is not erroneously judged as abnormal.
As described above, blood pressure of each patient follows a substantially same pattern of change during each dialysis treatment. Therefore, if a time-wise change of blood-pressure values of each patient during each dialysis treatment is stored in a memory device and the blood-pressure values (or the change of the blood-pressure values) stored in the memory device are compared with actual blood-pressure values (or change of the actual blood-pressure values) obtained during each dialysis treatment, only an abnormal blood-pressure change can be monitored during each dialysis treatment and accordingly an abnormal blood-pressure decrease can be quickly found without erroneously judging a normal blood-pressure change as abnormal. The present inventions have been developed based on these findings.
The above objects have been achieved by the present invention. According to a first feature of the present invention, there is provided a blood-pressure monitoring apparatus for use with a dialyzing device, comprising a blood-pressure-related-information obtaining device which iteratively obtains, from a patient who is undergoing a dialysis operation of the dialyzing device, a piece of blood-pressure-related information that can change in relation with a blood pressure of the patient; a change-value determining means for determining a change value representing a change of each piece of blood-pressure-related information iteratively obtained by the blood-pressure-related-information obtaining device; a memory device which stores, for the patient, a plurality of prescribed threshold values corresponding to a plurality of prescribed periods of an entire duration of the dialysis operation, wherein at least one of the threshold values that corresponds to at least one of the prescribed periods is smaller than the other threshold values, and wherein the blood pressure of the patient is more likely to lower during the at least one period of the entire duration, than during the other periods of the entire duration; and a judging means for judging that the blood pressure of the patient is abnormal, when the change value determined by the change-value determining means is greater than one of the threshold values that corresponds to one of the prescribed periods that includes a dialysis time, measured from a commencement of the dialysis operation, when the each piece of blood-pressure-related information is obtained by the blood-pressure-related-information obtaining device.
According to this invention, the change-value determining means determines a change value representing a change of
Colin Corporation
Hindenburg Max F.
Natnithithadha Navin
Oliff & Berridg,e PLC
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