Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv, Israel.
Int Wound J. 2018 Apr;15(2):243-249. doi: 10.1111/iwj.12857. Epub 2017 Nov 27.
Patients who are stationary endure prolonged soft tissue distortions and deformations at contact areas between their body and the support surface, which may lead to the onset of pressure ulcers (PUs) over time. A novel technology for patient positioning employs innovation in materials science, specifically viscoelastic materials with shape memory properties that compose the Z-Flo™ head positioner (Mölnlycke Health Care, Gothenburg, Sweden). Head positioners are generally known to reduce the occurrence of PUs in scalp tissues and the ears, but quantitative assessments of their biomechanical efficacy are missing in the literature. To determine potential differences in mechanical loads formed in the soft tissues of the back of the head while in contact with 2 head positioner types, Z-Flo vs flat medical foam, we developed 2 comparable finite element model configurations, both including the same 3-dimensional adult head. For both model variants, stresses in skin and fat peaked at the occiput. The skin at the back of the resting head is subjected to greater stress values with respect to fat; however, the Z-Flo positioner reduced the exposure of both skin and fat tissues to elevated stresses considerably (by a factor of 3) compared to the medical foam support. We found the Z-Flo device effective in reducing tissue loads at the surface of the head as well as internally in scalp tissues, with a particular strength in reducing internal tissue shear. The Z-Flo device achieves this protective quality through highly effective immersion and envelopment of the back of the head, generated in the process of manual moulding of the device in preparation for use. Additional protection is achieved through the viscoelastic response of the filling material of this positioner, which relaxes promptly and considerably under the weight of the head (by more than 2-fold within approximately 1 s) as opposed to the elastic recoil of the foam that pushes back on scalp tissues.
卧床患者在与支撑表面接触的身体部位会长期承受软组织扭曲和变形，随着时间的推移，可能会导致压疮（PU）的发生。一种新颖的患者定位技术采用了材料科学的创新，特别是具有形状记忆特性的粘弹性材料，构成了 Z-Flo™ 头部定位器（瑞典哥德堡 Mölnlycke Health Care）。头部定位器通常被认为可以减少头皮和耳朵部位的 PU 发生，但文献中缺乏对其生物力学效果的定量评估。为了确定与 2 种头部定位器类型（Z-Flo 与扁平医用泡沫）接触时，头部软组织中形成的机械负荷的潜在差异，我们开发了 2 种可比的有限元模型配置，均包含相同的 3 维成人头部。对于这 2 种模型变体，皮肤和脂肪在枕骨处的应力达到峰值。休息时头部后部的皮肤所受的压力值大于脂肪；然而，与医用泡沫支撑相比，Z-Flo 定位器大大降低了皮肤和脂肪组织暴露于高压力的程度（降低了 3 倍）。我们发现 Z-Flo 装置在减少头部表面以及头皮内部的组织负荷方面非常有效，在减少内部组织剪切方面尤其有效。Z-Flo 装置通过在使用前手动成型过程中对头部后部进行高度有效的浸没和包裹来实现这种保护质量。该定位器的填充材料的粘弹性响应进一步提供了额外的保护，该材料在头部重量的作用下迅速且显著地松弛（在大约 1 秒内超过 2 倍），而不是泡沫的弹性回弹，回弹会推回头皮组织。
