Abstract
In certifying eligibility for long-term care, in order to determine the level of need for long-term care, an examiner visits the applicant to evaluate their actual physical condition. However, the period of evaluation interview is usually limited, and thus assessment of the actual physical condition tends to be difficult. Taking these circumstances into consideration, we designed an ambulatory sensor system aimed at discriminating whether or not a subject uses assistance when standing up from a chair and sitting up in bed during daily activities. The system is composed of two accelerometers, one attached on the subject's chest and the other to the forearm. The chest accelerometer measures the angle in the gravitational direction and up-down motion acceleration. The forearm accelerometer measures the angle in the horizontal direction. In addition the sensor outputs are recorded in a compact data-logger. From experiments using 12 healthy subjects aged from 20 to 50 yrold, the present system could discriminate between the use of assistance (cane, desk and armrest) and no use of assistance when standing up. The periods of sitting up in bed were also detectable and the present system could discriminate between the use of assistance (bed handrail) and no use of assistance. The discriminating accuracy of the system was experimentally evaluated using four healthy subjects (aged 20 yr-old) and two elderly subjects (aged 72 and 73 yr-old). Preliminary experiments of ambulatory monitoring in normal living were also carried out using two elderly subjects (aged 72 and 69 yr-old). The results clearly demonstrated that the new system is able to distinguish with excellent accuracy (>90%) between using and not using assistance when standing up and sitting up in bed. We suggest that the system could be a useful means obtaining giving objective information in the procedure of certifying eligibility for long-term care.
