Mechanical Assessment of Tissue Properties During Tourniquet Application

Abstract

Introduction Successful tourniquet application increases survival rate of exsanguinating extremity hemorrhage victims. Tactile feedback during tourniquet application training should reflect human tissue properties in order to increase success in the field. This study aims to understand the mechanical properties of a human limb during tourniquet application. Method Six cadaveric extremities—three uppers and three lowers—were tested from three body mass index groups: low (<19) healthy (19-24), and overweight (>24). Each specimen donned with a tourniquet and mounted to a servo-hydraulic testing machine, which enabled controlled tightening of the tourniquet while recording the tourniquet tension force and strap displacement. A thin-film pressure sensor placed between the specimen and the tourniquet recorded contact pressure. Each limb was tested with the tourniquet applied at two different sites resulting in testing at the upper arm, forearm, thigh, and shank. Results The load displacement curves during radial compression were found to be nonlinear overall, with identifiable linear regions. Average contact pressure under the tourniquet strap at 200N and 300N of tension force was 126.3 (σ = 41.2) mm Hg and 205.3 (σ = 75.3) mm Hg, respectively. There were no significant differences in tissue stiffness or contact pressure at 300N of tension force between limb (upper vs. lower) or body mass index. At 200N of tension, the upper limb had significantly higher contact pressure than the lower limb (P = 0.040). Relative radial compression was significantly different between upper (16.74, σ = 4.16%) and lower (10.15, σ = 2.25%) extremities at 200N tension (P = 0.005). Conclusions Simulation of tissue compression during tourniquet application may be achieved with a material exhibiting elastic properties to mimic the force-displacement behavior seen in cadaveric tissue or with different layers of material. Different trainers for underweight, healthy, and overweight limbs may not be needed. Separate tourniquet training fixtures should be created for the upper and lower extremities.

Applied use of biomechanical measurements from human tissues for the development of medical skills trainers: a scoping review

“…During full-text review, study citations were examined, and 20 articles were identified and included. A total of 186 papers 29–31,33–215 were included for data extraction.…”

“…This meant that the biomechanical tissue properties were assumed to be the same, even though multiple tissues comprised the structure. Twenty-one of the included studies assessed tissues as composites 31,37,46,49,51,63,71,72,95,102,103,109,122,136,144,146,155,158,163,170,185 . Of the composites assessed, 6 focused on soft tissue composites (eg, skin and underlying structures), 31,37,102,103,158,185 9 on structures associated with the spine, 46,49,95,109,122,136,146,155,170 5 on joints, 46,63,72,144,163 and 1 on vocal cords 71 …”