Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
1999-09-09
2001-02-20
O'Connor, Cary (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S485000, C600S494000, C600S500000
Reexamination Certificate
active
06190325
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a blood-pressure monitoring apparatus which monitors a blood pressure of a living subject.
2. Related Art Statement
As information relating to a pulse wave which propagates through an arterial vessel of a living subject, there are known a pulse-wave-propagation time DT and a pulse-wave-propagation velocity V
M
(m/s). The pulse-wave-propagation time DT is a time which is needed by a pulse wave to propagate between two different positions of the arterial vessel. Additionally, it is known that the above pulse-wave-propagation-relating information is, within a predetermined range, substantially proportional to the blood pressure (“BP”, mmHg) of the living subject. Therefore, there has been proposed a BP monitoring apparatus which determines, in advance, coefficients a, B in the following expression: EBP=&agr;(DT)+&bgr; (where &agr; is a negative constant and &bgr; is a positive constant), or EBP=&agr;(V
M
)+&bgr; (where a and &bgr; are positive constants), based on two measured BP values of the subject and two measured pulse-wave-propagation time values (DT) or two measured pulse-wave-propagation velocity values (V
M
), iteratively determines an estimated BP value EBP of the subject, based on each set of subsequently obtained pulse-wave-propagation-relating information, according to the above-indicated first or second expression, and starts a BP measurement using an inflatable cuff when an abnormal estimated BP value EBP is determined. An example of the BP monitoring apparatus is disclosed in U.S. Pat. No. 5,752,920.
Meanwhile, the elasticity or flexibility of blood vessels of a patient as a living subject may be lost due to arteriosclerosis or temporary constriction of the blood vessels. In this case, the BP of the patient cannot be easily controlled. Therefore, it is needed to quickly measure a BP value of the patient and quickly make a decision about whether or not any treatments should be given to the patient. This is also the case with a patient who has fallen in shock because of excessive expansion of the blood vessels upon administration of a hypotensive drug.
In addition, a relationship between pulse-wave-propagation-relating information and estimated BP value EBP changes depending upon a hardness of a blood vessel for which the pulse-wave-propagation-relating information is obtained. That is, the coefficient &agr; of each of the above-indicated two expressions that defines the relationship between pulse-wave-propagation-relating information and estimated BP value EBP changes depending upon the hardness of the blood vessel. Therefore, if the hardness of the blood vessel largely changes while estimated BP values EBP are iteratively determined for monitoring the BP of the patient, the accuracy of the estimated BP values EBP decreases, which may lead to delaying commencement of a BP measurement using the inflatable cuff.
SUMMERY OF THE INVENTION
It is therefore an object of the present invention to provide a blood-pressure monitoring apparatus which early starts a blood-pressure measurement using an inflatable cuff, when information relating to the circulatory system of a living subject satisfies a predetermined condition.
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 (21). 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 includes an inflatable cuff adapted to apply a pressing pressure to a body portion of a living subject and which measures at least one blood-pressure value of the living subject by changing the pressing pressure of the inflatable cuff; a pulse-wave-propagation-relating-information obtaining device which iteratively obtains a piece of pulse-wave-propagation-relating information relating to propagation of a pulse wave through an arterial vessel of the living subject; estimating means for iteratively estimating a blood-pressure value of the living subject, based on each piece of pulse-wave-propagation-relating information of a plurality of pieces of pulse-wave-propagation-relating information obtained by the pulse-wave-propagation-relating-information obtaining device, according to a predetermined relationship between pulse-wave-propagation-relating information and blood pressure; starting means for starting, when a value based on the estimated blood-pressure value does not fall within a predetermined first range, a blood-pressure measurement of the measuring device; index-value calculating means for calculating, based on the at least one blood-pressure value of the living subject measured by the measuring device, an index value indicative of a hardness of a blood vessel of the living subject; and range changing means for changing, when the calculated index value does not fall within a predetermined second range, the predetermined first range to a changed first range which is contained in the predetermined first range and is narrower than the predetermined first range. In the present blood-pressure (“BP”) monitoring apparatus, the range changing means changes, when the calculated index value does not fall within the predetermined second range, the predetermined first range to the changed first range which is contained in the predetermined first range and is narrower than the predetermined first range. Thus, the starting means can earlier start the blood-pressure measurement of the measuring device. For example, in the case where the elasticity or flexibility of blood vessels of the living subject has been lost or the blood vessels of the subject are excessively expanded, the measuring device can earlier measure a BP value of the subject.
(2) According to a second feature of the present invention that includes the first feature (1), the blood-pressure monitoring apparatus further comprises relationship determining means for determining the relationship between pulse-wave-propagation-relating information and blood pressure, based on at least one blood- pressure value of the living subject measured by the measuring device and at least one piece of pulse-wave-propagation-relating information obtained by the pulse-wave-propagation-relating information obtaining device.
(3) According to a third feature of the present invention, there is provided a blood-pressure monitoring apparatus comprising a measuring device which includes an inflatable cuff adapted to apply a pressing pressure to a body portion of a living subject and which measures at least one blood-pressure value of the living subject by changing the pressing pressure of the inflatable cuff; a pulse-wave-propagation-relating-information obtaining device which iteratively obtains a piece of pulse-wave-propagation-relating information relating to propagation of a pulse wave through an arterial vessel of the living subject; estimating means for iteratively estimating a blood-pressure value of the living subject, based on each piece of pulse-wave-propagation-relating information of a plurality of pieces of pulse-wave-propagation-relating information obtained by the pulse-wave-propagation-relating-information obtaining device, according to a predetermined relationship between pulse-wave-propagation-relating information and blood pressure; starting means for starting, when a value based on to the estimated blood-pressure value does not fall within a predetermined first range, a blood-pressure measurement of the measuring device; index-value calculating means for calculating, based on the at least one blood-pressure value of the living subject measured by the measuring device, an index value indicative of a hardness of a blood vessel of the living subject; change-va
Carter Ryan
Colin Corporation
O'Connor Cary
Oliff & Berridge PLC.
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