Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2001-11-02
2003-11-11
Hindenburg, Max F. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S490000, C600S500000
Reexamination Certificate
active
06645156
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a continuous blood-pressure monitoring apparatus which includes a pressure-pulse-wave sensor adapted to be pressed against an artery of a living subject via the skin and continuously monitors blood pressure of the subject based on a pressure pulse wave detected by the sensor.
2. Related Art Statement
There is known a continuous blood-pressure monitoring apparatus which includes an inflatable cuff adapted to be worn on a portion of a living subject; a blood-pressure determining means for determining a blood pressure of the subject based on a signal obtained while a pressure in the cuff is slowly changed; a pressure-pulse-wave detecting device which includes a pressure-pulse-wave sensor adapted to be pressed against an artery of a prescribed portion of the subject and continuously detects a pressure pulse wave produced by the artery; a relationship determining means for determining, in advance, a relationship between blood pressure and magnitude of pressure pulse wave, based on the blood pressure determined by the blood-pressure determining means and a magnitude of the pressure pulse wave detected by the pressure-pulse-wave detecting device; and a blood-pressure monitoring means for successively determining, according to the thus determined relationship, a blood-pressure value of the subject based on each of respective magnitudes of the pressure pulse wave detected by the pressure-pulse-wave detecting device. Since the blood-pressure values successively determined by the continuous blood-pressure monitoring apparatus are very highly reliable, the apparatus can be used in those cases in which strict blood-pressure monitoring is needed. This apparatus is disclosed in, e.g., Japanese Utility Model Document No. 2-82309 or its corresponding U.S. Pat. No. 5,139,026.
In the continuous blood-pressure monitoring apparatus, disclosed in the above-indicated document, in which the pressure-pulse-wave sensor is pressed against an artery of a prescribed portion of a living subject, a condition under which the sensor is pressed against the artery may be changed by, e.g., a change of a state in which the sensor is worn, caused by a physical motion of the subject. Hence, in order to increase the reliability of blood-pressure values determined by the blood-pressure monitoring means, a calibration is periodically carried out to update the relationship between blood pressure and magnitude of pressure pulse wave. In each calibration, the blood-pressure determining means determines a new blood pressure of the subject in a process in which the pressure of the cuff is changed in a prescribed manner, and the relationship determining means determines a new relationship between blood pressure and magnitude of pressure pulse wave, based on the new blood pressure determined by the blood-pressure determining means and a magnitude of the pressure pulse wave detected by the pressure-pulse-wave sensor during the above-indicated process.
However, when each calibration is carried out, the cuff is inflated to press the subject's portion, thereby causing the subject to feel discomfort. In addition, the calibration is periodically carried out irrespective of whether the condition under which the sensor is pressed is appropriate or not, and the calibration period needs to be shortened to increase the reliability of continuous monitoring of blood pressure. Thus, the burden exerted on the subject is increased.
In order to solve the above-indicated problem, Japanese Patent Document No. 7-284479 or its corresponding U.S. Pat. No. 5,860,932 discloses a continuous blood-pressure monitoring apparatus in which a pressure-pulse-wave sensor is worn on a portion of a subject that is located on a downstream side of a cuff, a pressure of the cuff is increased at a prescribed rate, and a judging means judges whether a relationship between blood pressure and pressure-pulse-wave magnitude is appropriate, based on a shape or an area of a pressure pulse wave detected by the sensor during the increasing of the cuff pressure. More specifically described, the disclosed apparatus determines, in a state in which the cuff pressure would be substantially equal to, or somewhat higher than, a diastolic blood pressure of the subject, the diastolic blood pressure of the subject by utilizing the fact that the tendency of change of respective shapes or areas of respective heartbeat-synchronous pulses of the pressure pulse wave, successively detected by the sensor during the increasing of the cuff pressure, significantly changes around the diastolic blood pressure, compares the thus determined diastolic blood pressure with a diastolic blood pressure determined based on a magnitude of a heartbeat-synchronous pulse of the pressure pulse wave according to the relationship between blood pressure and pressure-pulse-wave magnitude, and judges whether the relationship is appropriate. If it is judged that the relationship is appropriate, then it is not needed to carry out a calibration, which leads to reducing the discomfort the subject suffers.
However, even in the above-described continuous blood-pressure monitoring apparatus, the cuff pressure is increased up to a value substantially equal to, or somewhat higher than, the diastolic blood pressure, so as to judge whether the relationship is appropriate or not. Thus, the discomfort the subject suffers is not sufficiently reduced.
In addition, in the above-described continuous blood-pressure monitoring apparatus, the pressure-pulse-wave sensor needs to be worn on the subject's portion located on the downstream side of the cuff. On the other hand, in many cases, the continuous blood-pressure monitoring apparatus is used during a surgical operation or in an intensive care unit when or where many devices are connected to the subject and, in some cases, the pressure-pulse-wave sensor cannot be worn on the subject's portion located on the downstream side of the cuff.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a continuous blood-pressure monitoring apparatus which sufficiently reduces discomfort felt by a living subject and sufficiently increases freedom of wearing.
The above object has been achieved by the present invention. According to a first aspect of the present invention, there is provided an apparatus for continuously monitoring a blood pressure of a living subject, comprising an inflatable cuff which is adapted to be wound around a portion of the subject, a cuff pulse wave including a plurality of heartbeat-synchronous pulses occurring to the cuff while a pressure in the cuff is changed; a blood-pressure determining means for determining a blood pressure of the subject based on a signal obtained while the pressure of the cuff is changed; a pressure-pulse-wave detecting device which includes a pressure-pulse-wave sensor that is adapted to be pressed against an artery of the subject and which continuously detects, through the pressure-pulse-wave sensor, a pressure pulse wave that is produced by the artery and includes a plurality of heartbeat-synchronous pulses; a relationship determining means for determining a relationship between blood pressure and magnitude of pressure pulse wave, based on the blood pressure determined by the blood-pressure determining means and a magnitude of the pressure pulse wave detected by the pressure-pulse-wave detecting device; a blood-pressure monitoring means for iteratively determining, according to the thus determined relationship, a monitor blood-pressure value of the subject based on a magnitude of each of the heartbeat-synchronous pulses of the pressure pulse wave detected by the pressure-pulse-wave detecting device; a pulse-wave-propagation-velocity-related-information obtaining means for iteratively obtaining, in a state in which the pressure of the cuff is held at a prescribed pulse-wave-detection pressure lower than a diastolic blood pressure of the subject, a piece of pulse-wave-propagation-velocity-related information
Colin Corporation
Hindenburg Max F.
Natnithithadha Navin
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