下肢の支持性が低下した人に対する移乗サポートロボットを用いての立ち上がり動作の検証

Abstract

背景 高齢化が進む中で人間の基本的な生活行動に看護支援が必要な人々が増加するとともに、看護する側である看護者または介護者の腰痛は多発する状況にある。特に、車椅子移乗援助に伴う看護者の腰部負担率は高く、これは在宅で要介護者を介護する家族にとっても同様である。このため、移乗援助に看護支援が必要な人々に対してその自立を目ざしサポートするとともに、リフトやロボットなどの移乗支援機器を開発し適切な活用法を見いだすことは、サポートが必要な人の自立のみならず看護または介護する者の腰部負担軽減にとって急務である。目的 本研究では、移乗動作をサポートする試作ロボットを用いて、下肢の支持性が低下した人に対する車椅子移乗動作のうち、立ち上がり動作についての筋電図による分析を行う。また、同被験者に対して実験に伴う主観的反応やロボットを用いての使いやすさ等の調査を行う。これらの結果をもとに、ロボットを用いての有効な立ち上がり動作について検証する。方法 1.対象および研究方法 2004年3月、以下の実験および調査を実施した。被験者は、両下肢の支持性低下を想定した平均的体格の男子学生4名と女子学生4名とした。実験は、被験者の重心をロボットに近づけてほぼ垂直に立ち上げる方法(垂直法)と被験者を前傾させながら立ち上げる方法(前傾法)の比較検証とした。分析は、表面筋電図測定装置SX230(8ch仕様)を用いて、動作実験結果をもとに各被験筋についての筋積分値を算出し検証した。尚、同被験者に対して、作業直後にロボットを用いての使いやすさ・安心感、主観的反応についての調査を行った。2.倫理的配慮 対象は研究の趣旨に同意した者のみとし、研究参加に同意した後でもいっでも辞退可能であること。また、プライバシーの保護についても文書と口頭で伝えた。結果 下肢の支持性が低下した人を想定した被験者8名に対するロボットを用いての立ち上がり動作実験を行った結果、動作開始から13秒間の筋積分値では、垂直法において上腕部・前腕部および背部の筋積分値は顕著に高値を示し、前傾法と比較して立ち上がり動作時に筋疲労をより多く伴うことが明らかとなった。また、実験に伴う主観的反応を調査した結果、垂直法では特に前腕部の苦痛症状は高値であり、ロボットを用いての使いやすさや安心感も低値を示した。一方、前傾法ではロボットを用いての使いやすさや安心感は高いものの胸部・腹部の苦痛症状は高値を示した。結論 下肢の支持性が低下した人に対するロボットを活用しての立ち上がり動作では、垂直に立ち上がる方法は被験者の腕部に筋疲労および苦痛を大きく伴い活用は困難と考えられた。一方、前傾にしながら立ち上がる方法では筋疲労は比較的低く、胸部や腹部など身体に密着する側に改善を加えれば有効に活用できる可能性はあると考えられた。

Background The graying of the Japanese society and the increase in the number of people seeking assistance to carry out some of the basic everyday activities have resulted in an increased incidence of low back pain among nurses and caregivers. Assisting individuals particularly in transferring into and out of a wheelchair puts a lot of strain on the low back. This is true not only for nurses but also for those individuals caring for a family member with support needs. In order to prevent low back pain among nurses and caregivers, it is imperative that a range of transfer aids (such as, lifts and robots) be developed and utilized. At the same time, individuals with support needs should be provided with the means to achieve independence in daily living activities. Objective This study was conducted to analyze electromyographic (EMG) activity during a robotassisted standing transfer in individuals with reduced lower limb strength. A standing transfer consists of moving from a seated to a standing position. An experimental robot, which was designed to assist people in standing transfers, was used. Subjects were surveyed regarding the usability of the robot and the subjective response associated with a robot-aided standing transfer. Based on the results obtained from the experiment and the survey, practicability of the robot as a transfer aid was evaluated in terms of user safety and comfort. Method 1. Subjects and Methods: The following experiment and survey were conducted in March, 2004. Subjects were four male university students and four female university students who had been trained to simulate individuals with reduced lower limb strength. In the experiment, the robot was first placed very close to the subjects, who were asked to lean on the robot to get up to a standing position while barely bending their upper body forward as they were being raised (A method). Secondly, the robots were placed slightly further from the subjects, thus enabling the subjects to bend their upper body forward as they were raised to a standing position (B method). A surface electromyograph called SX230 (8ch type) was used to calculate the integral of the electromyogram signals (EMG integral) for each tested muscle. Following the experiment, subjects were surveyed regarding the usability/reliability of the robot and the subjective response associated with robotassisted standing transfer. 2. Ethical Consideration: All subjects were fully informed of the purpose of the study before consenting to participate in the study, and were fully aware that they could withdraw from the study at any time. They were also fully informed both orally and in writing about their right to privacy. Results The results of the present study can be summarized as follows: The EMG integral for each tested muscle was calculated for the first 13 seconds of a standing transfer. The EMG integrals for the biceps, forearms, and dorsum were markedly large when the A method was used to raise the subjects to a standing position. Furthermore, the A method caused greater muscle fatigue compared to the B method. According to the survey regarding the pain associated with a robot-assisted standing transfer, patients reported considerable pain in the forearms when the A method was used, which led to a decreased usability and reliability of the robot. On the other hand, although usability and reliability of the robot were relatively high when the B method was followed, the subjects reported some pain in the chest and the abdomen. Conclusions To sum up, the A method is not suitable for individuals with reduced lower limb strength because it causes great pain and strain in the arms. In contrast, muscle fatigue induced by the B method was relatively mild, and with a few modifications to the part of the robot which comes into contact with the user's chest and abdomen, the robot may have a potential to become auseful tool for assisting individuals in a standing transfer.