安全なベッドからの立ち上がりに関する研究(その2) : 表面筋電図を用いた成人患者の下肢筋力の検討

Abstract

背景 臨床でのベッドの高さは,車椅子からの移動がしやすく,足底が床に着き立ち上がりや腰掛に容易で,ベッドから転倒・転落の危険性が少ないなど,高さ設定に安全性安楽性が求められる.しかし,われわれの調査では,臨床の患者に適したベッドの高さ設定については看護師との差異があり,高さ設定の種々の要因を追究することが必要とされた.目的 様々なベッドの高さでの立ち上がりに要する下肢筋群の活動を表面筋電図にて測定した.即ち,筋力が低下した状況にある患者に対して,どのような高さ設定が安全であるのかを年代ごとの身体計測値並びに活動筋電位にて検討を加えた.方法 健康な20歳から70歳代の女性83名を対象とした.個々の身体計測と下肢筋力測定を行った後に,ベッドからの立ち上がり時に使用される下肢筋群の表面筋電図測定を,下腿高に対する100%,120%,140%の高さ比率となる3段階で測定し,年代間比較を行なった.結果 立ち上がりに必要な下肢筋力を総合評価する垂直跳び,長座体前屈及び握力は,年齢と共に低下していたが,最大筋活動電位の年代差は認められなかった.立ち上がり時の筋活動は,三段階のいずれの高さにおいても大腿直筋が最も高い筋活動を示し,次いで,大腿二頭筋,前脛骨筋,腓腹筋の順となった.また,100%のベッドの高さでは全ての筋の活動率が高くなり,筋肉に対する負荷が上昇していた.さらに,筋活動率は年齢が高くなるに従い増加した.結論 従来,示されていた下腿高と同じベッドの高さは,患者が適していると考えるベッドの高さよりも立ち上がりに筋活動を要し,下肢筋力の低下している者にとっては負担がかかる.患者のベッドの高さ設定においては,身長や下腿高の身体寸法だけでなく,年齢や下肢筋力の程度をも考慮して安全性を高めることが望ましいと考える.

Background Hospital beds should be adjusted to a safe and comfortable height in order to enable patients to transfer either to a wheelchair or to a standing or a seated position with minimal difficulties, to ensure that the soles of a patient's feet can be placed flat on the floor in a seated position, and to minimize the risk of fall injuries. Yet, few hospitals adjust the height of beds in such a way as to meet the needs of individual patients. Objective Surface electromyogram (SEMG) was used to measure the patients' lower limb muscle activity as they transferred to a standing position from beds adjusted to three different heights. Body size and myoelectric potential values of patients were compared by age group in order to determine the safe bed height for patients with weakened muscles. Methods Eighty-three female subjects whose ages ranged from 20 to 79 years were included in the present study. Firstly, their body size and muscle strength were measured. Secondly, SEMG was used to record the activity of lower limb muscles in these subjects as they moved from a seated to a standing position using hospital beds. This measurement was taken for each of the following three bed heights: 100%, 120%, and 140% the leg length. Thirdly, comparison was made across the different age groups. Results At all bed heights measured, the most active lower limb muscle was the rectus femoris, followed by biceps femoris, tibialis anterior, and gastrocnemius. Activities in all lower limb muscles were maximal when the height of the bed was adjusted to 100% the leg length, indicating that the muscle load can be reduced by using higher beds. Regardless of bed height, higher muscle activities were observed in older subjects. Conclusion In Japan, it has been customary to adjust the bed height to equal the patient's leg length. However, this type of bed height imposes relatively great strain on patients when they try to move to a standing position. This is particularly true in patients whose lower limb muscles are weakened. In order to ensure that a patient can safely shift to a standing position, not only the body measurement (e.g., height and leg length) but also the age and the lower limb muscle strength of a patient should be considered when adjusting the bed height.