Numerical analysis of ischemia- and compression-induced injury in tissue-engineered skeletal muscle constructs

Effect of Vibration on Alleviating Foot Pressure-Induced Ischemia under Occlusive Compression

Objectives

Foot ulcers often occur in people with diabetes because of pressure-induced tissue ischemia. Vibration has been reported to be helpful in alleviating mechanical damage and promoting wound healing. The objective of this study is to explore whether vibration can relieve reactive hyperemia in foot tissue under occlusive compression.

Methods

Thirteen healthy adults participated in the study. Each foot was placed under occlusive compression without or with vibration intervention, which was randomly assigned every other day. The dorsal foot skin blood flow (SBF) was measured pre- and postintervention for each subject in each test. Temporal variations and spectral features of SBF were recorded for comparison.

Results

The results showed that subjects displayed an obvious reactive hyperemia in the foot tissue after pressure occlusion, whereas they displayed a more regular SBF when vibration was applied along with occlusive compression. Moreover, the amplitude of metabolic, neurogenic, and myogenic pathways for SBF was significantly reduced during the hyperemia process when vibration was applied.

Conclusions

This study demonstrated that vibration can effectively reduce the level of hyperemia in foot tissue under occlusive compression and also induce less protective physiological regulatory activities. This is helpful for protecting foot tissue from pressure-induced ischemic injury and foot ulcers.

New Clinically Relevant Method to Evaluate the Life Span of Prophylactic Sacral Dressings

It has been demonstrated that wound dressings provide a protective effect against pressure injuries. However, no method exists to measure either the life or performance of dressings used in prevention; testing dressings in a clinical setting or a research environment has typically been based on measuring its moisture absorption capacity. This article examines the changes that occur in the structural and mechanical properties of a prophylactic dressing based on conditions of use when wound exudate is not present.A clinically relevant method was developed to simulate the loading, friction-inducing shear, and moisture transpiration present in a typical hospitalization where a dressing is applied for prevention. Single-use dressings were tested using this method to evaluate their ability to protect patients from pressure injuries throughout the typical 5 to 7 days of use. Following this aging process, researchers measured the physical, structural, and mechanical changes in prophylactic dressings over time.This innovative method provides guidance for clinicians on dressing use and replacement intervals. For bioengineers, the method generates important empirical data for computer modeling of dressing performance, which can then reveal the consequences of changes in dressing structure and function on sustained tissue loads. It is the authors' hope to generate discussion about the creation of industry-wide standards for testing dressings to improve patient care.

Measuring Tensile Strength to Better Establish Protective Capacity of Sacral Prophylactic Dressings Over 7 Days of Laboratory Aging

Results from large-scale randomized clinical trials support the application of prophylactic dressings to provide protection from body-weight force-induced deformations known to damage skin and underlying tissues, which often result in pressure injuries (pressure ulcers). This laboratory study using a new method for aging dressings in simulated use followed by tensile testing was conducted to further understand the protective effect of sacral prophylactic dressings (SPDs) in alleviating tissue deformations in the sacral region through the course of typical application. Specifically, four SPDs were exposed to a simulation of the clinical environment incorporating saline solution absorption, mechanical loading, and repetitive sliding-induced shear. After aging, the protective endurance of the SPDs was measured through tensile testing to determine their effectiveness against tissue-damaging forces over time.This study uses the concepts of axial stiffness, protective endurance, and elastic limit to describe more accurately the protective aspects of SPDs under dry and moist conditions and how they interact with the skin and underlying tissues over the life of the dressing. The authors propose two primary features in SPD effectiveness in preventing pressure injuries: high conformability (ie, low flexural stiffness) and protective endurance (the dressing's capacity to maintain biomechanical performance when moist).