Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2000-04-27
2001-12-25
Nasser, Robert L. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S492000, C600S497000
Reexamination Certificate
active
06332869
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for measuring a superior-and-inferior-limb blood-pressure index of a living subject (e.g., a ratio of an inferior-limb blood pressure to a superior-limb blood pressure, or a ratio of a superior-limb blood pressure to an inferior-limb blood pressure).
2. Related Art Statement
For a person who suffers arterial obstruction or arteriostenosis, his or her inferior-limb blood pressure (“BP”) value should be lower than his or her corresponding superior-limb BP value (f or example, a systolic superior-limb BP value corresponds to a systolic inferior-limb BP value). Meanwhile, if an inferior-limb BP value of a person is higher than his or her corresponding superior-limb BP value by a certain value, he or she may suffer aortic incompetence or aortitis syndrome limited to aortic arch. It has been practiced to utilize these facts for diagnosing arterial disease based on a ratio of an inferior-limb BP value to a superior-limb BP value, or a ratio of a superior-limb BP value to an inferior-limb BP value, i.e., a superior-and-inferior-limb blood-pressure index.
Generally, the above superior-and-inferior-limb blood-pressure index (hereinafter, abbreviated to the “SIL BP index”) is obtained or calculated as the ratio of a systolic BP value of an ankle as the inferior-limb BP value to a systolic BP of an upper arm as the superior-limb BP value, that is, ankle brachial index (abbreviated to “ABI”) or ankle/arm BP index (abbreviated to “AAI” or “API”). If a measured ankle/arm BP index of a living person is smaller than a threshold, e.g., about 0.9, abnormality may be diagnosed on the person. Thus, even a small change of the inferior-limb or superior-limb BP value greatly affects the diagnosis.
The BP of a living person can change even in a short time. For example, the BP of a living person at rest can physiologically change by more than 20 mmHg in ten seconds. Therefore, if there is a time difference between a first time when a systolic BP is measured from an inferior limb and a second time when a systolic BP is measured from a superior limb, the BP of the person may change during the time difference. However, the conventional SIL BP index measuring device cannot enable an observer to judge, when there is a difference between an inferior-limb BP value and a superior-limb BP value, whether that difference is caused by the timewise BP change of the person or by the fact that the two BP values are measured from the different body portions of the person. Thus, the accuracy of the superior-and-inferior-limb blood-pressure index determined based on the two BP values is not sufficiently high.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a superior-and-inferior-limb blood-pressure (“SIL BP”) index measuring apparatus which can measure a highly accurate SIL BP index value of a person.
The Applicants have carried out various studies and have found that if a time when an inferior-limb BP value is measured coincides with a time when a superior-limb BP value is measured, it can be judged that the difference between the inferior-limb BP value and the superior-limb BP value is caused by only the fact that the two BP values are measured from the different body portions of the person. The present invention has been developed based on this finding.
(1) According to a first feature of the present invention, there is provided an apparatus for measuring a superior-and-inferior-limb blood-pressure index of a living subject, comprising an inferior-limb blood-pressure measuring device which includes a first inflatable cuff adapted to be wound around an inferior limb of the subject, and which measures an inferior-limb blood pressure of the subject based on a first pulse wave obtained while a first pressing pressure of the first cuff is changed; a superior-limb blood-pressure measuring device which includes a second inflatable cuff adapted to be wound around a superior limb of the subject, and which measures a superior-limb blood pressure of the subject based on a second pulse wave obtained while a second pressing pressure of the second cuff is changed; a cuff-pressure changing device which changes the first and second pressing pressures of the first and second cuffs, such that a time when the first pressing pressure being changed becomes equal to an estimated inferior-limb blood pressure coincides with a time when the second pressing pressure being changed becomes equal to an estimated superior-limb blood pressure; and index determining means for determining the superior-and-inferior-limb blood-pressure index of the subject, based on the inferior-limb and superior-limb blood pressures measured by the inferior-limb and superior-limb blood-pressure measuring devices while the first and second pressing pressures of the first and second cuffs are changed by the cuff-pressure changing device.
According to this feature, the cuff-pressure changing device changes the first and second pressing pressures of the first and second cuffs, such that the time when the first pressing pressure being changed becomes equal to the estimated inferior-limb blood pressure coincides with the time when the second pressing pressure being changed becomes equal to the estimated superior-limb blood pressure. While the cuff-pressure changing device changes the first and second pressing pressures of the first and second cuffs in this way, the inferior-limb and superior-limb blood pressures are measured by the inferior-limb and superior-limb blood-pressure measuring devices, respectively. The index determining means determines the superior-and-inferior-limb blood-pressure index of the subject, based on the thus measured inferior-limb and superior-limb blood pressures. Therefore, the present apparatus can provide highly accurate superior-and-inferior-limb blood-pressure index values.
(2) According to a second feature of the present invention that includes the first feature (1), the apparatus further comprises estimated-inferior-limb-blood-pressure determining means for operating, before the cuff-pressure changing device changes the first and second pressing pressures of the first and second cuffs, the inferior-limb blood-pressure measuring device to measure an inferior-limb blood pressure of the subject, and determining the measured inferior-limb blood pressure as the estimated inferior-limb blood pressure; and estimated-superior-limb-blood-pressure determining means for operating, before the cuff-pressure changing device changes the first and second pressing pressures of the first and second cuffs, the superior-limb blood-pressure measuring device to measure a superior-limb blood pressure of the subject, and determining the measured superior-limb blood pressure as the estimated superior-limb blood pressure.
According to this feature, the estimated-inferior-limb-blood-pressure determining means operates, before the cuff-pressure changing device changes the first and second pressing pressures of the first and second cuffs, the inferior-limb blood-pressure measuring device to measure an inferior-limb blood pressure of the subject, and determines the thus measured inferior-limb blood pressure as the estimated inferior-limb blood pressure, and the estimated-superior-limb-blood-pressure determining means operates, before the cuff-pressure changing device changes the first and second pressing pressures of the first and second cuffs, the superior-limb blood-pressure measuring device to measure a superior-limb blood pressure of the subject, and determines the thus measured superior-limb blood pressure as the estimated superior-limb blood pressure. Therefore, the present apparatus can assure that the time when the inferior-limb blood pressure to be used to determine the blood-pressure index is measured accurately coincides with the time when the superior-limb blood pressure to be used to determine the blood-pressure index is measured. Thus, the present apparatus can provide more highly accurate blood-pressure index values.
Nunome Tomohiro
Ogura Toshihiko
Colin Corporation
Nasser Robert L.
Natnithithadha Navin
Oliff & Berridg,e PLC
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