Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
1999-09-20
2001-06-05
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S493000, C600S490000, C600S496000
Reexamination Certificate
active
06241680
ABSTRACT:
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 without causing the subject to feel serious discomfort.
2. Related Art Statement
There is known a blood-pressure (“BP”) monitoring device which monitors the blood pressure of a living subject such as a patient. The BP monitoring device includes a BP measuring device which includes an inflatable cuff adapted to be wrapped around a body portion (e.g., upper arm) of a patient and which measures one or more BP values of the patient by changing the air pressure in the inflatable cuff wrapped around the upper arm of the patient. The BP monitoring device periodically starts a BP measurement of the BP measuring device at a predetermined period. However, this BP monitoring device has the problem that if the BP measuring device starts a BP measurement at a shorter period, for improving the reliability of monitoring of the BP monitoring device, the inflatable cuff more frequently presses the upper arm of the patient and causes the patient to feel serious discomfort.
In this situation, there has been proposed another BP monitoring device which includes a pulse-wave detecting device which detects a pulse wave which is produced in an inflatable cuff when the cuff presses an upper arm of a patient; a pressure control device which repeatedly increases the pressing pressure of the inflatable cuff (hereinafter, referred to as the “cuff pressure”) up to a predetermined pressure value lower than a mean BP value of the patient, with a predetermined pause being inserted between each pair of repeated cuff-pressure increasing operations; a change-rate calculating means or circuit which calculates the rate of change of respective amplitudes of heartbeat-synchronous pulses of the pulse wave detected by the pulse-wave detecting device when the cuff pressure is increased to the predetermined pressure value by the pressure control device, with respect to the cuff pressure increased by the pressure control device; and an abnormality judging means or circuit which judges, based on the calculated rate of change, whether the patient has an abnormal BP value. This BP monitoring device is disclosed in, e.g., U.S. Pat. No. 5,649,536. Since the BP monitoring device changes the cuff pressure in a low pressure range from the atmospheric pressure to the predetermined pressure value, and monitors the BP of the patient based on the rate of change of the pulse amplitudes obtained during the changing of the cuff pressure, it does not cause the patient to feel serious discomfort.
However, even in the above-indicated second BP monitoring device, the inflatable cuff repeatedly presses the upper arm of the patient, though the pressing pressure of the cuff, i.e., the cuff pressure is not increased to a high pressure value. If the frequency of pressing of the cuff is increased to improve the reliability of the BP monitoring device, the patient may feel serious discomfort.
Meanwhile, there has also been proposed yet another BP monitoring device which iteratively calculates an index value indicative of a condition of a circulatory system of a patient and monitors a change of the BP of the patient based on a change of each of the calculated index values. The index value may be one which is indicative of a condition of circulation of blood in the patient and which can be non-invasively obtained without pressing any body portions of the patient. For example, the index value may be a piece of pulse-wave-propagation (“PWP”) relating information, such as a PWP velocity or a PWP time, that relates to propagation of a pulse wave through an arterial vessel of the patient; a piece of pulse-relating information, such as a pulse rate (i.e., heart rate) or a pulse period; or a piece of blood-flow-amount-relating information, such as a peripheral-pulse-wave area, that relates to an amount of flow of blood through a peripheral body portion of the patient. The third BP monitoring device is disclosed in, e.g., U.S. Pat. No. 5,776,071. The disclosed BP monitoring device iteratively calculates, as the index value, a value relating to each of heartbeat-synchronous pulses of a volumetric pulse wave obtained from a patient, and monitors the BP of the patient based on a change of each calculated value. When the third BP monitoring device finds a significant change of each calculated value (i.e., each index value), it starts a BP measurement of a BP measuring device using an inflatable cuff, so as to obtain one or more reliable BP values of the patient. However, if too low a reference value is employed to find a change of each index value, for the purpose of improving the reliability of the BP monitoring device, the cuff would too frequently press the upper arm of the patient and would cause the patient to feel serious discomfort.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a blood-pressure monitoring apparatus which monitors the blood pressure of a living subject with a high reliability without causing the subject to feel serious discomfort.
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 (14). 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 an inflatable cuff adapted to apply a pressing pressure to a body portion of a living subject; a cuff-pulse-wave detecting device which detects a cuff pulse wave which is produced in the inflatable cuff when the inflatable cuff applies the pressing pressure to the body portion of the living subject, the cuff pulse wave comprising a plurality of heartbeat-synchronous pulses; a pressure control device which increases the pressing pressure of the inflatable cuff to a predetermined value lower than a mean blood-pressure value of the living subject; index-value calculating means for iteratively calculating an index value indicative of a condition of a circulatory system of the living subject; starting means for judging whether each of the index values calculated by the index-value calculating means is abnormal and, when the each index value is judged as being abnormal, starting the pressure control device to increase the pressing pressure of the inflatable cuff to the predetermined value; change-rate calculating means for calculating a rate of change of respective amplitudes of the heartbeat-synchronous pulses of the pulse wave detected by the pulse-wave detecting device when the pressing pressure of the inflatable cuff is increased to the predetermined value by the pressure control device, with respect to the pressing pressure of the inflatable cuff increased by the pressure control device; and abnormality judging means for judging, based on the calculated rate of change, whether the living subject has an abnormal blood-pressure value. In the present BP monitoring apparatus, the pressure control device increases the pressing pressure of the inflatable cuff, for judging whether the BP of the subject is abnormal, when the calculated index value indicative of the condition of the circulatory system of the subject is judged as being abnormal, i.e., there is a great possibility that the BP of the subject is abnormal. Thus, in the present apparatus, the cuff less frequently presses the body portion of the subject than a conventional apparatus in which a cuff periodically presses a body portion of a subject at a predetermined short period. In addition, the present apparatus can monitor the BP of the subject with a high reliability.
(2) According to a second feature of the present invention that includes the first feature (1), the monitoring apparatus further comprises a measuring device whic
Colin Corporation
Natnithithadha Navin
Oliff & Berridg,e PLC
Winakur Eric F.
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