Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
1999-09-17
2001-02-13
O'Connor, Cary (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S490000, C128S925000, C706S015000
Reexamination Certificate
active
06186953
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for iteratively estimating an intra-arterial blood-pressure value of a living subject, based on information non-invasively obtained from a circulatory system of the subject.
2. Related Art Statement
There is known an automatic blood-pressure (“BP”) measuring device which non-invasively measures an intra-arterial BP value of a living subject, such as a “Korotkoff-sound-type” BP measuring device or an “oscillometric-type” BP measuring device. The Korotkoff-sound-type BP measuring device determines a BP value of a subject based on the first and/or last detection of Korotkoff sounds produced when a pressing pressure of a pressing belt wrapped around a body portion of the subject is changed, and the oscillometric-type BP measuring device determines a BP value of a subject based on variation of respective amplitudes of heartbeat-synchronous pulses produced when a pressing pressure of a pressing belt is changed.
Meanwhile, in an operation room or an intensive care unit, it may be required to periodically measure a BP value of a patient at the shortest possible period, so that a medical staff can give one or more urgent treatments to the patient. However, in the above-indicated prior BP measuring device, no BP values can be obtained before several tens of seconds have passed from the commencement of operation of the measuring device. In the case where a BP value of a patient is periodically measured at a very short period, the body portion of the patient around which the pressing belt is wrapped may suffer congestion due to the frequency compression of the pressing belt, and the obtained BP values may include errors due to the congestion of the patient.
In this background, there has been proposed a non-invasive and continuous BP estimation device which calculates, based on a signal non-invasively obtained from a living subject, a velocity at which a pulse wave propagates through an arterial vessel of the subject, and continuously estimates a BP value of the subject based on the calculated velocity according to a predetermined relationship. This BP estimation device is disclosed in, e.g., Japanese Utility Model Application laid open for inspection purposes under Publication No. 7(1995)-9305 and Japanese Patent Application laid open for inspection purposes under Publication No. 7-308295.
However, the above-identified BP estimation device estimates a BP value based on only a pulse-wave propagation velocity or a pulse-wave propagation time, and accordingly cannot enjoy a satisfactory accuracy of estimation of BP values. Thus, the prior BP estimation device needs to frequently calibrate itself based on one or more BP values measured by a Korotkoff-sound-type or oscillometric automatic BP measuring device using a pressing belt.
SUMMERY OF THE INVENTION
It is therefore an object of the present invention to provide a non-invasive and continuous blood-pressure estimation apparatus which can estimate blood pressure values of a living subject with a high accuracy.
The present invention provides a blood-pressure estimating apparatus which has one or more of the technical features that are described below in respective paragraphs given parenthesized sequential numbers (1) to (13). 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 an apparatus for iteratively estimating an intra-arterial blood-pressure value of a living subject, based on information non-invasively obtained from a circulatory system of the subject, the apparatus comprising a pulse-wave-propagation-relating-information obtaining device which non-invasively and 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; a circulation-relating-information obtaining device which non-invasively and iteratively obtains a piece of circulation-relating information comprising at least one of a piece of heartbeat-relating information relating to heartbeat of the living subject and a piece of pulse-wave-area-relating information relating to area of a heartbeat-synchronous pulse of a volumetric pulse wave obtained from a peripheral body portion of the living subject; and blood-pressure estimating means comprising a neural network which learns a plurality of sets of information each set of which comprises a blood-pressure value measured using an inflatable cuff, a piece of pulse-wave-propagation-relating information obtained when the blood-pressure value is measured using the cuff, and at least one of a piece of heartbeat-relating information obtained when the blood-pressure value is measured using the cuff and a piece of pulse-wave-area-relating information obtained when the blood-pressure value is measured using the cuff, the neural network iteratively estimating an intra-arterial blood-pressure value of the living subject, based on each piece of pulse-wave-propagation-relating information iteratively obtained by the pulse-wave-propagation-relating-information obtaining device and at least one of each piece of heartbeat-relating information and each piece of pulse-wave-area-relating information which is iteratively obtained by the circulation-relating-information obtaining device. The present BP estimating apparatus estimates a BP value of a living subject such as a patient based on not only the pulse-wave-propagation-relating information but also at least one of the heartbeat-relating information as a parameter which relates to the central portion of the circulatory system of the subject and changes in relation to the BP of the subject and the pulse-wave-area-relating information which relates to a peripheral portion of the circulatory system of the subject and changes in relation to the BP of the subject. Thus, the present apparatus can more accurately estimate BP values of the subject than a conventional apparatus which estimates a BP value of a living subject based on pulse-wave-propagation-relating information only.
(2) According to a second feature of the present invention that includes the first feature (1), the blood-pressure estimating apparatus further comprises a blood-pressure measuring device which includes an inflatable cuff adapted to apply a pressing pressure to a body portion of the living subject and which measures a blood-pressure value of the living subject by changing the pressing pressure of the inflatable cuff, and the blood-pressure estimating means further comprises modifying means for modifying the neural network based on comparison of the blood-pressure value of the living subject measured by the measuring device, and the blood-pressure value of the subject estimated by the blood-pressure estimating means when the blood-pressure value is measured by the blood-pressure measuring device. In the present BP estimating apparatus, the modifying means modifies the neural network, so that the neural network is adapted for an individual living subject such as an individual patient. Thus, the present apparatus can more accurately estimate BP values of the subject.
(3) According to a third feature of the present invention that includes the first or second feature (1) or (2), the neural network learns the plurality of sets of information each set of which comprises the blood-pressure value measured using the inflatable cuff, the piece of pulse-wave-propagation-relating information obtained when the blood-pressure value is measured using the cuff, the piece of heartbeat-relating information obtained when the blood-pressure value is measured using the cuff, and the piece of pulse-wave-area-relating information obtained when the blood-pressure value is measured using the cuff, and wherein the blood-pressure estimating means iteratively estimates an intra-arterial blood-pressure value of the living subject, based on each piece o
Colin Corporation
Natnithithadha Navin
O'Connor Cary
Oliff & Berridg,e PLC
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