Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2000-05-30
2001-11-13
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S587000
Reexamination Certificate
active
06315736
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an anesthetic-depth monitor apparatus which monitors an anesthetic depth of a living subject who is undergoing a surgical operation. The anesthetic depth means a degree of suppression of pain or consciousness of the subject.
2. Related Art Statement
It is desirable that the degree of anesthesia of a patient who is undergoing a surgical operation be not too shallow nor too deep, that is, be kept at an appropriate level. To this end, it has conventionally been practiced to monitor the anesthetic depth of a patient by measuring the change of his or her blood pressure, heart rate, or respiration rate in response to the surgical stimuli, or observing his or her cilium reflex or pupil's diameter, or the color or temperature of his or her limb or peripheral body portion. In addition, U.S. Pat. Nos. 5,871,450 and 5,964,713, assigned to the Assignee of the present application, disclose an anesthetic-depth measuring device which determines an anesthetic depth based on the ratio of peripheral body temperature to deep body temperature, and an anesthetic-depth measuring device which determines an anesthetic depth based on the fluctuations of pulse period or blood pressure.
However, in some cases, the conventional devices may not enjoy the highest reliability. For example, in the case where a conventional device is used to monitor the anesthetic depth of a patient to keep it at an appropriate level, the anesthesia may not be kept sufficiently deep so that the patient may be awaken, which causes the patient to feel much discomfort. To avoid this, it is likely to administer, in an actual surgical operation, too much anesthetic agent to the patient. However, the administration of too much anesthetic agent delays the awakening of the patient after the operation. In addition, the consumption of too much anesthetic agent is not economical.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an anesthetic-depth monitor apparatus which can monitor, with high reliability, an anesthetic depth of a living subject who is undergoing a surgical operation.
The Inventors have carried out extensive studies and researches, and have found the following facts: The objects of general anesthesia include not only the above-indicated suppression of consciousness and pain but also the relaxation of muscles. Those three items, that is, the suppression of consciousness, the suppression of pain, and the muscular relaxation are related to one another. For example, when a patient has consciousness, he or she feels strong pain, whereas a patient may not physically react, because of his or her muscular relaxation, against pain though he or she has consciousness. Therefore, it is desirable that the anesthetic depth be monitored by using at least two items of the above-indicated two items. However, each of the conventional anesthetic-depth measuring devices or methods measures an anesthetic depth based on only one of the three items, and accordingly may not have enjoyed the highest reliability. For example, the conventional method in which anesthetic depth is monitored based on change of blood pressure of a patient in response to surgical stimuli, is related to only the suppression of pain; and the anesthetic-depth measuring devices disclosed in the above-indicated U.S. Patents is related to only the level of activity of nerve, i.e., the suppression of consciousness or the degree of arousal. The present invention has been developed based on these findings.
(1) According to a first feature of the present invention, there is provided an apparatus for monitoring an anesthetic depth of a living subject, comprising at least two devices of (a) an arousal-index determining device which determines an arousal index indicating a degree of arousal of the subject, (b) a pain-index determining device which determines a pain index indicating a degree of pain of the subject, and (c) a muscular-relaxation-index determining device which determines a muscular-relaxation index indicating a degree of muscular relaxation of the subject; and an anesthetic-depth determining means for determining, based on at least two indexes determined by the at least two devices, an anesthetic depth of the subject according to a predetermined relationship between anesthetic depth and the at least two indexes.
According to this feature, the anesthetic-depth monitor apparatus determines an anesthetic depth of the subject based on at least two of the arousal index, the pain index, and the muscular-relaxation index of the subject. Therefore, the present apparatus can determine a highly reliable anesthetic depth.
(2) According to a second feature of the present invention, there is provided an apparatus for monitoring an anesthetic depth of a living subject, comprising an arousal-index determining device which determines an arousal index indicating a degree of arousal of the subject; a pain-index determining device which determines a pain index indicating a degree of pain of the subject; a muscular-relaxation-index determining device which determines a muscular-relaxation index indicating a degree of muscular relaxation of the subject; and an anesthetic-depth determining means for determining, based on the determined arousal index, the determined pain index, and the determined muscular-relaxation index, an anesthetic depth of the subject according to a predetermined relationship between (A) anesthetic depth and (B) (b
1
) arousal index, (b
2
) pain index, and (b
3
) muscular-relaxation index.
According to this feature, the anesthetic-depth monitor apparatus determines an anesthetic depth of the subject based on the arousal index, the pain index, and the muscular-relaxation index of the subject. Therefore, the present apparatus can determine a very highly reliable anesthetic depth.
(3) According to a third feature of the present invention that includes the first or second feature (1) or (2), the monitor apparatus comprises the arousal-index determining device, and the arousal-index determining device comprises a pulse-wave sensor which detects a pulse wave including a plurality of heartbeat-synchronous pulses each of which is produced in synchronism with a heartbeat of the subject; pulse-period-relating-information obtaining means for successively obtaining a batch of pulse-period-relating information relating to a pulse period at which the each heartbeat-synchronous pulse is produced in synchronism with the heartbeat of the subject; means for determining a magnitude of a high-frequency component of fluctuations of the batches of pulse-period-relating information successively obtained by the pulse-period-relating-information obtaining means, the high-frequency component having a high frequency substantially equal to a frequency of respiration of the subject; means for determining a magnitude of a low-frequency component of the fluctuations of the batches of pulse-period-relating information, the low-frequency component having a low frequency substantially equal to a predetermined fraction of the frequency of respiration of the subject; and means for determining the arousal index based on a ratio of the magnitude of the low-frequency component to the magnitude of the high-frequency component.
(4) According to a fourth feature of the present invention that includes any one of the first to third features (1) to (3), the monitor apparatus comprises the pain-index determining device, and the pain-index determining device comprises a pulse-wave sensor which detects a pulse wave including a plurality of heartbeat-synchronous pulses each of which is produced in synchronism with a heartbeat of the subject; pulse-period-relating-information obtaining means for successively obtaining a batch of pulse-period-relating information relating to a pulse period at which the each heartbeat-synchronous pulse is produced in synchronism with the heartbeat of the subject; pulse-period-relating-information-change determining means for determining a change of the bat
Tsuda Hideichi
Tsutsumi Yoshiaki
Colin Corporation
Natnithithadhi Navin
Oliff & Berridg,e PLC
Winakur Eric F.
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