Hydrocolloids are a dressing containing a gel-forming agent such as sodium carboxymethylcellulose (NaCMC), pectin and gelatin. In many products, these are combined with elastomers and adhesives and applied to a carrier - usually polyurethane foam or film, to form an absorbent, self adhesive, waterproof dressing. There are many differences in structure, flexibility, dimensions, and fluid handling properties between commercially available hydrocolloid dressings (Thomas et.al 2004).

The primary physical functions of hydrocolloid dressings are to:

  • produce a moist wound environment thus facilitation of autolytic debridement

  • management of exudate

  • provision of a barrier to micro-organisms

The SMTL are able to test the following characteristics of hydrocolloid dressings:


British Pharmacopoeia 1993 Addendum 1996 - Semi-Permeable Hydrocolloid Dressings
  • Uniformity of weight

  • Waterproofness (UKAS accredited)

  • Adhesiveness (UKAS accredited)

  • Extensibility (UKAS accredited)

  • pH

  • Fluid Handling Capacity (UKAS accredited)

BS EN 13726 Test methods for primary wound dressings
  • Fluid Handling Capacity - EN 13726-1 Section 3.2 (UKAS accredited)

  • Waterproofness - BS EN 13726-3 (UKAS accredited)

  • Conformability (Extensibility and Permanent Set) - BS EN 13726-4 (UKAS accredited)


SMTL in-house developed methods to BS EN 13726 Test methods for primary wound dressings
  • Conformability - SMTL TM-16

  • Conformability SMTL/Queen Method - SMTL TM-16 modified


Conformability - SMTL TM-16

In this test, the wound dressing is clamped over the apparatus and then pressurised.  The pressure required for the dressing to dome to a specific height (2cm) is recorded via a pressure transducer.  The pressure required to dome the dressing is inversely proportional to the conformability i.e. the higher the pressure required to reach the 2cm height, the less conformable the dressing.

Conformability - SMTL TM-16 modified

The SMTL/Queen method is a modificatoin of TM-16 and is based on the publication Queen et.al 1987 Biomaterials

         

      Conform Close up  

In this test, the wound dressing is set up as above, and then inflated to 40mmHg.  The height the dressing reaches is proportional to the conformability of the dressing i.e. the higher the dressing height, the higher the dressing conformability.  It is also possible to calculate the radius of curvature from the dressing inflation height. 

 

 

 

 

If you wish to commission testing of your hydrocolloid dressings, then contact the SMTL:

Surgical Materials Testing Laboratory, Princess of Wales Hospital, Coity Road, Bridgend, UK, CF31 1RQ.

Tel: +44 (0) 1656 752820
Email: physical@smtl.co.uk

 

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