Rigid Junctional Tourniquet Effector Heads: Forces, Pressures, and Pressure Gradients Accompanying Target Artery Occlusion

Abstract

Junctional tourniquets capable of controlling haemorrhage from distal sites are being actively developed for pre-hospital and emergency settings. One category of device uses a rigid mechanical effector head to occlude a target artery. It is important to minimize the forces, pressures, and pressure gradients used in order to avoid tissue and organ damage and to ensure subject comfort and safety. However, little is known about the magnitude of the forces and pressures necessary in order to affect artery occlusion with such devices. This work is a preliminary instrumental exploration of the pressure and force parameter space likely to arise when rigid mechanical tourniquet effector heads are used to occlude junctional arteries. Interface pressure data are measured for a commercially available system, namely the Combat Ready Clamp (CRoC), using biomedical interface pressure transducers (BIPTs) embedded in flexible low-profile pads sandwiched between the CRoC effector head and the target tissue site. Occlusion is produced in both iliac and femoral arteries at peak interface pressures in the range of 250–275 mmHg. A dynamometer is used to simultaneously measure the force applied to the actuator handle of improvised effector heads while also logging the interface pressure using either embedded or pad-based BIPT arrays. Measured forces in the range of 175–220 N and average interface pressures in the range of 250–310 mmHg are found to produce iliac and femoral artery occlusion using these improvised effector heads. Correct effector head location over a target artery can significantly reduce the forces required to affect occlusion. For instance, the force required to occlude the iliac artery using improvised effector heads is reduced from 175 to 110 N using an integrated Doppler probe to locate the target artery.