Surgery – Diagnostic testing – Cardiovascular
Patent
1997-01-27
1999-02-16
Nasser, Robert L.
Surgery
Diagnostic testing
Cardiovascular
600500, A61B 500
Patent
active
058714502
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE ART
The present invention relates to an anesthetic depth measuring apparatus for measuring an anesthetic depth of a living subject.
BACKGROUND OF THE INVENTION
When a patient is anesthetized for a surgery or the like, it is required to maintain a suitable anesthetic depth so as to protect the patient from stress or pain due to the surgery. Conventionally, for example, an anesthetic depth has been subjectively or empirically recognized by monitoring a change of a blood pressure, a heart rate or a respiration rate of the patient, resulting from a stimulation of the surgery, or observing a reflex of eyelashes, a dimension of a pupil, a hue of a limb or a body temperature of the patient.
However, since the anesthetic depth recognition based on the change of the blood pressure, the heart rate or the respiration rate, or based on the reflex of the eyelashes, the dimension of the pupil, the hue of the limb or the body temperature is performed depending on a subjective judgement of anesthetists or the like, the anesthetists are required to have a long-time experience and a skill. In addition, it is not easy to objectively or accurately recognize the anesthetic depth. It is therefore an object of the present invention to provide an anesthetic depth measuring apparatus for objectively measuring an anesthetic depth of a living subject.
The inventors of the present invention have continued their study in the background of the above described situation, and they have found that a magnitude of a pulse period fluctuation component produced in synchronism with a respiration of a subject, a magnitude of a blood pressure fluctuation component having a frequency lower than a frequency of the respiration of the subject or a rate of change of the pulse period to the blood pressure of the subject has a close relation to an activity level of subject's parasympathetic nerve or sympathetic nerve, whereby an anesthetic depth of the subject can be objectively measured on the basis of the magnitude of the above mentioned fluctuation component, when the subject is anesthetized.
Moreover, the present inventors have found that the influences of the anesthesia on a peripheral body temperature and a deep body temperature are different from each other, and a difference between the peripheral body temperature and the deep body temperature has a close relation to an activity level of a nerve of the subject, whereby an anesthetic depth of the subject can be objectively measured on the basis of the difference. The present invention has been developed based on those findings.
DISCLOSURE OF THE INVENTION
The above object may be achieved according to the first invention which provides an anesthetic depth measuring apparatus for measuring an anesthetic depth of a living subject, characterized by comprising: (a) a pulse period measuring device which continuously measures a period of a pulse of the subject; (b) pulse period fluctuation signal extracting means for extracting, from a fluctuation of the pulse periods continuously measured by the pulse period measuring device, a first pulse period fluctuation signal which corresponds to a first pulse period fluctuation component produced in substantial synchronism with a respiration of the subject and a second pulse period fluctuation signal which corresponds to a second pulse period fluctuation component having a predetermined frequency lower than a frequency of the first pulse period fluctuation component; and (c) anesthetic depth calculating means for calculating an anesthetic depth of the subject based on a ratio of the first pulse period fluctuation signal to the second pulse period fluctuation signal.
In the above mentioned apparatus, from a fluctuation of the pulse periods continuously measured by the pulse period measuring device, the first pulse period fluctuation signal which corresponds to the first pulse period fluctuation component produced in substantial synchronism with the respiration of the subject and the second pulse period fluctuation signal which corresponds to t
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patent: 4788982 (1988-12-01), Gedeon et al.
patent: 5390679 (1995-02-01), Martin et al.
patent: 5632272 (1997-05-01), Diab et al.
Nomura Takashi
Tsuda Hideichi
Colin Corporation
Nasser Robert L.
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