The Design and Development of Active Compression Garments for Orthostatic Intolerance

Abstract

Current compression garments are often made from a spandex-type elastic material with static levels of compression and can become uncomfortable and difficult to don/doff [1]. This limits their usability, especially for unhealthy or aging populations. The only current alternative to elastic compression stockings are inflatable compression sleeves that are controllable, but highly immobile and must be tethered to an inflation source [2]. Neither design offers a solution that is simultaneously low profile, mobile, and controllable. Here we present the design and development of compression garments with embedded shape-changing materials that can produce controllable compression without the need for a bulky inflation system. This active materials approach enables dynamic control over the degree, timing and location of compression, and allows for graded, synchronized, pulsed, and peristaltic compression patterns, which provide the medical benefit of moving fluid in the body [2]. Such a design combines the best features of both elastic and inflatable compression garments: a slim, low-profile form factor that is easy to don/doff and provides dynamic control. Shape memory alloy (SMA) coil actuators, as described by Holschuh et al., [3] have the ability to apply compressive forces to the body when paired with passive textiles and wrapped circumferentially around the body. These actuators are engineered to contract when heated, creating controllable forces and displacements that are modulated through an applied current. SMA compression garments (SMA-CG) have important applications, from consumer uses to clinical interventions, including: augmenting venous return for conditions of orthostatic intolerance (e.g., postural orthostatic tachycardia syndrome (POTS)); cardiac rehabilitation in heart failure patients; lymphedema venous insufficiency; reducing deep vein thrombosis (DVT) risk; sports performance; and countermeasures for flight or space flight. While the potential uses for this technology are broad, the basic design is similar across many conditions. Key research areas include: 1) identifying and addressing design considerations relevant to prototype development of SMA-CG; 2) determining the compression thresholds needed to dynamically oppose orthostatic changes; and 3) evaluating the effectiveness of the prototypes for augmented venous return by synchronizing compression during cardiac diastole. Here, we focus on the first question: design of SMA-CG prototypes.