1. Field of the Invention
The present invention relates to an apparatus for evaluating a degree of recovery of a living subject from a surgical operation.
2. Related Art Statement
A living subject who has undergone a surgical operation is monitored, in, e.g., a recovery room, with respect to blood pressure, heart rate, blood oxygen saturation, etc. Based on the blood pressure, heart rate, and/or blood oxygen saturation being monitored, a doctor judges, from his or her experience, whether the subject has recovered from the surgical operation and, if it is judged that the subject has recovered, then the subject is moved to a general ward. The judgment made in this manner about the degree of recovery of the subject from the operation is more or less unclear, but it is not problematic so long as the subject is kept in hospital.
Meanwhile, recently, a day operation has become popular. The day operation means that in a single day a patient undergoes a surgical operation and goes home. If a judgment made by a doctor about a postoperative condition of a patient who has undergone a day operation is unclear, then the condition of the patient may become worse after the patient goes home. After the patient goes home, the doctor cannot do a quick treatment on the patient. Thus, it has been needed to objectively or quantitatively evaluate a postoperative condition of a living subject.
It is therefore an object of the present invention to provide an apparatus which can objectively and accurately evaluate a degree of recovery of a living subject from a surgical operation.
To this end, the Inventors have carried out an extensive study and have found that information relating to the circulatory organ of a living subject who has undergone a surgical operation largely and randomly changes from its values before the operation, because of anesthesia or physical stimuli administered or applied to the subject during the operation. However, after the operation, the circulatory-organ-relating information will change toward its values before the operation. The Inventors have found such a phenomenon that the circulatory-organ-relating information obtained after the operation will become stable around a certain saturation value, and such a fact that the change of circulatory-organ-relating information obtained after the operation is closely related to the degree of recovery of the subject from the operation. The present invention has been developed based on those findings.
The above object has been achieved by the present invention. According to the present invention, there is provided an apparatus for evaluating a degree of recovery of a living subject from a surgical operation which the subject has undergone, the apparatus comprising a circulatory-organ-relating-information obtaining means for iteratively obtaining, after the operation, a piece of circulatory-organ-relating information relating to a circulatory organ of the subject; and a recovery-degree evaluating means for evaluating the degree of recovery of the subject, based on at least one piece of circulatory-organ-relating information obtained by the circulatory-organ-relating-information obtaining means.
In the present apparatus, the circulatory-organ-relating-information obtaining means iteratively obtains, after the surgical operation, a piece of circulatory-organ-relating information relating to the circulatory organ of the living subject, and the recovery-degree evaluating means evaluates the degree of recovery of the subject, based on one or more pieces of circulatory-organ-relating information obtained by the circulatory-organ-relating-information obtaining means. Thus, present apparatus can objectively and accurately evaluate the degree of recovery of the subject from the operation which the subject has undergone.
Peferably, the recovery-degree evaluating means comprises means for evaluating the degree of recovery of the subject, by judging whether a change of a plurality of pieces of circulatory-organ-relating information iteratively obtained by the circulatory-organ-relating-information obtaining means is smaller than a reference value and accordingly is stable. There is a phenomenon that the pieces of circulatory-organ-relating information iteratively obtained from the postoperative subject by the circulatory-organ-relating-information obtaining means change toward a saturation value and become stable around the same. Since the recovery-degree evaluating means evaluates the degree of recovery of the subject, by judging whether a change of the pieces of circulatory-organ-relating information is smaller than a reference value and accordingly is stable, the present apparatus can objectively and accurately evaluate the degree of recovery of the subject from the operation.
Preferably, the circulatory-organ-relating-information obtaining means comprises means for iteratively obtaining, as a piece of circulatory-organ-relating information, one selected from the group consisting of a blood pressure Value, a heart rate value, a magnitude of a fluctuation of blood pressure values, and a magnitude of a fluctuation of heart rate values. There is a phenomenon that the blood pressure values, heart rate values, magnitudes of fluctuation of blood pressure values, or magnitudes of fluctuation of heart rate values, iteratively obtained from the postoperative subject by the circulatory-organ-relating-information obtaining means change toward a saturation value and become stable around the same. Thus, the present apparatus can evaluate, based on a change of those values, the degree of recovery of the subject from the operation.
Preferably, the recovery-degree evaluating means comprises means for determining a saturation value based on a time-wise change of a plurality of pieces of circulatory-organ-relating information iteratively obtained by the circulatory-organ-relating-information obtaining means, means for determining, based on the saturation value, a reference value smaller than the saturation value, and means for evaluating the degree of recovery of the subject, by judging whether a piece of circulatory-organ-relating information obtained by the circulatory-organ-relating-information obtaining means is greater than the reference value. The pieces of circulatory-organ-relating information iteratively obtained from the postoperative subject by the circulatory-organ-relating-information obtaining means have a nature to change along a logarithmic curve, and accordingly can be expressed by a logarithmic function. Therefore, a saturation value of the information can be determined, for each living subject, based on a time-wise change of the information. Since the recovery-degree evaluating means evaluates the degree of recovery of the subject, by judging whether an actual piece of circulatory-organ-relating information is greater than the reference value lower than the saturation value, the present apparatus can accurately evaluate the degree of recovery of the subject, independent of individual differences of living subjects.
Preferably, the circulatory-organ-relating-information obtaining means comprises means for iteratively obtaining, as a piece of circulatory-organ-relating information, one selected from the group consisting of a magnitude of a low-frequency fluctuation of blood pressure values, and a ratio of one of a magnitude of a low-frequency fluctuation of heart rate values and a magnitude of a high-frequency fluctuation of the heart rate values to the other of the magnitude of low-frequency fluctuation of heart rate values and the magnitude of high-frequency fluctuation of heart rate values, and the recovery-degree evaluating means comprises means for evaluating the degree of recovery of the subject, by judging whether the one selected from the group is greater than a reference value. It is speculated that the magnitude of low-frequency fluctuation of blood pressure values of the subject, or the ratio of one of the magnitude of low-frequency fluctuation of heart rate values and the magnitude of high-frequency fluctuation of the heart rate values to the other of the magnitude of low-frequency fluctuation of heart rate values and the magnitude of high-frequency fluctuation of heart rate values faithfully reflects the activity of the sympathetic nerve system of the subject. Since the recovery-degree evaluating means evaluates the degree of recovery of the subject, by judging whether a blood pressure value or the ratio is greater than a reference value, the present apparatus can objectively and accurately evaluate the degree of recovery of the subject from the operation.
Preferably, the circulatory-organ-relating-information obtaining means comprises means for iteratively obtaining, as a piece of circulatory-organ-relating information, one selected from the group consisting of a frequency distribution of fluctuations of blood pressure values, and a frequency distribution of fluctuations of heart rate values, and means for determining a degree of sharpness of the one selected from the group, and the recovery-degree evaluating means comprises means for evaluating the degree of recovery of the subject, by judging whether the determined degree of sharpness is greater than a reference value. The sharpness-degree values of the frequency distribution of fluctuations of blood pressure values or the frequency distribution of fluctuations of heart rate values, iteratively obtained from the postoperative subject change toward a value before the operation. Since the recovery-degree evaluating means evaluates the degree of recovery of the subject, by judging whether a sharpness degree of the frequency distribution is greater than a reference value, the present apparatus can objectively and accurately evaluate the degree of recovery of the subject.
Preferably, the circulatory-organ-relating-information obtaining means comprises means for iteratively obtaining, as a piece of circulatory-organ-relating information, one selected from the group consisting of a frequency spectrum of fluctuations of blood pressure values, and a frequency spectrum of fluctuations of heart rate values, and means for determining a proportion of an interval fluctuation magnitude of the one selected from the group in a prescribed frequency interval, with respect to a whole fluctuation magnitude of the one selected from the group in a whole frequency range, and the recovery-degree evaluating means comprises means for evaluating the degree of recovery of the subject, by judging whether the determined proportion is greater than a reference value. The proportion of interval fluctuation magnitude of the frequency spectrum of fluctuations of blood pressure values or the frequency spectrum of fluctuations of heart rate values, iteratively obtained from the postoperative subject, change toward a value before the operation. Since the recovery-degree evaluating means evaluates the degree of recovery of the subject, by judging whether a proportion of interval fluctuation magnitude of the frequency spectrum is greater than a reference value, the present apparatus can objectively and accurately evaluate the degree of recovery of the subject.