壓瘡常見於老年人或長期臥床病患上，其成因為人體軟組織長時間受壓迫，微血管變形，使得血液輸送困難，導致組織缺氧、壞死。治療壓瘡的程序繁複、耗時且醫療費用龐大，並常伴隨併發症，增加死亡率。人體與床墊間之壓力是引起壓瘡的主要原因，因此評估床墊的力學性質成為臨床護理人員之重要工作。
然而現行床墊之壓力測試系統需專業操作，且價格昂貴，因此醫護理人員對於病患使用的床墊不易隨時進行床墊壓力檢測。本研究主要的目的為發展一簡易型的床墊負荷與變形關係量測器具，並實際進行床墊測試，分析床墊的材料性質。另選定常發生壓瘡之人體薦椎部位進行有限元素分析，以實驗結果配合模擬分析探討床墊受壓力與變形之關係，進而推估人體組織受壓力之耐受時間，以供護理人員在照護上之參考。
本研究以醫療院所常用之床墊為對象，並使用本研究開發之量具，分別以砝碼固定重量及手臂施予彈簧特定伸長量兩種方式，進行床墊材質測試。分析實驗結果發現，床墊發生永久變形區域，其楊氏係數較小，容易發生床墊觸底（bottom out）而與下方之硬實床板接觸，使得界面壓力提高。另外對照組之實驗結果顯示，本研究設計之量具直接以手操作是可以被接受的。有限元素分析發現，軟組織層之等效應力最大值發生在薦骨外側邊緣處，且越靠近骨頭則應力越大，且除薦骨末端區域外，軟組織與硬床墊接觸時應力較大，反之則較小。
將床墊實驗結果與有限元素相互分析比對，定義出量具量取之參數與組織耐壓時間之關係。以本研究之測試床墊為例，其組織耐壓時間為3至4小時，因此本研究建議護理人員為長期臥床病患翻身時間間隔應小於3小時，而現行護理人員每2小時即為病患翻身，此間隔包含在本研究建議時間內，因此本研究之結果是合理的。

Pressure ulcers are common in elderly or bed-ridden patients. They are caused by compression of soft tissue and capillary deformation, which will lead to decreased capillary blood flow, hypoxia and soft tissue necrosis in the long term. The treatment of pressure ulcers is cumbersome, time-consuming and costly. Pressure ulcers often accompany complications, which increases the mortality rate. The pressure between body and mattress is one of the main causes for pressure ulcers. Therefore it is important for clinical nurses to assess the mechanical properties of the mattress.
The current pressure test system of mattress normally is operated by a professional technician and is inconvenient for a nursing staff to measure the mattress pressure at any time. Therefore, the purpose of this study is to develop an easy-operated instrumentation which is capable of analyzing the material properties of mattress by measuring the load and deformation. In addition, the simulations were carried out by using the finite element analysis on sacrum, where pressure ulcers happen most often. By means of comparing analysis results with experimental data, the relation between pressure and deformation can be obtained and the tolerance time of soft tissue can be determined as the reference to the nursing staff for caring.
In the study, the designed instrumentation was utilized to measure the material property of commonly medical mattress by the fixed weight and a specific spring elongation operated by hand, respectively. The experimental results showed that the Young's modulus is less in the permanent deformation area of the mattress and may prone to the mattress bottoming out and contact with the hard bed board below the mattress, increase the interface pressure. The testing results by the fixed weight and a specific elongation by hand were similar and they show that the design of this study can be operated by either ways. The result of finite element analysis shows that the maximum equivalent stress occurred at the outer edge of sacrum, and closer to the bone the greater tress occurred. Except for the region of the inferior sacrum, the stress will be larger when soft tissue contact with harder mattress.
Analyze the results of experiment and finite element, and then define the relationship between the parameters of measurement and the tolerance time of soft tissue. As an example of the test mattress in this study, the tolerance time is about 3-4 hours, so this study suggests that time interval should be less than three hours for a nursing staff to turn the bed-ridden patients over. The current nursing staff turn the patients over once every 2 hours, and this interval is within the proposed time of this study, so the results of this study is reasonable.

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