Fabric system to combat deep vein thrombosis

Advances in Textiles Technology, Nov, 2008

CalfPad has been designed to help reduce the incidences of deep vein thrombosis (DVT) that may occur in patients requiring surgical procedures.

Originally invented by two young UK surgeons--and further developed for volume production by Novamedix, based in Andover, UK--each CalfPad comprises a set of air-filled inflation bladders, held in place around the patient's calf, within a series of fabric layers.

In clinical applications, a pair of CalfPads is linked to the Novamedix A-V Impulse System--a device which mimics the natural physiological processes that maintain blood circulation in the legs and arms--before being applied to the patient's lower limbs.

With the special design of the bladder,a targeted impulse compression is applied to the patient's calf.

Commencement of therapy results in intermittent and rapid inflation of the CalfPads, initiating high velocity and turbulent venous return in the lower limbs. This mimics the physiological process of walking with full weight bearing, considered to be the best way to prevent DVT.

By replacing the natural process of walking, CalfPad significantly reduces venous stasis, the principal factor for DVT formation. The CalfPad device can be used by patients in bed or sitting at rest. A variety of other Novamedix disposable garments are available for circulation enhancement to reduce the complications associated with immobility.

Produced in three sizes, the CalfPad required careful design and fabric engineering to ensure that clinicians can target the regular pulses on appropriate areas of the limb. Design for production involved specialist assembly of airtight inflation bladders, encompassed in multiple layers of biocompatible fabric. These include the inflation bladders, radiofrequency-welded (RF-welded) from polyurethane (PU), laminate polyvinyl chloride (PVC), nonwoven polyesters and a foam layer with a skin contact face of brushed polyamide (PA).

As part of the project, Arrow Medical, based in Kington, UK, designed a series of RF welding techniques to produce the inflatable air bladders from medical grade PU, then bonded all the layers into a single piece.

The production of leak-free air bladders is critical to ensure long-life and operational efficiency. Arrow Medical says it has developed a set of specialist techniques using various RF welding procedures to establish complete reliability and consistency in volume production runs.

Arrow Medical's production planners handled all aspects of production build-up, from prototyping to limited market release, with a rapid transition to full market release as soon as Novamedix acceptance trials were successfully completed. All products of this type are supported by Arrow Medical's metrology team, which carries out life and conformance tests to ensure appropriate standards are met.

Arrow has worked with Novamedix to maintain standards and minimize labour and material costs within a continuous improvement programme, which includes complete product traceability back to raw material suppliers. Arrow manages labelling, logistics and stockholding and applies clinical and operating instructions to both the CalfPad and packaging for wholesale distribution and clinical centres.

For further information, contact: John Johnson, Arrow Medical Ltd, Hatton Gardens Industrial Estate, Kington, Herefordshire HR5 3RB, UK. Tel: 1544-231760. Fax: 1544-231640. E-mail: john@arrowmedical.co.uk; http://www.arrowmedical.co.uk; or: Novamedix Services Ltd, Viscount Court, South Way, Walworth, Andover, Hampshire, SP10 5NW, UK. Tel: 1264-334212. Fax: 1264-334007. Email: avi@orthofix.com; http://www.orthofix.com/avimpulse; or: http://www.a-vimpulsesystem.co.uk