Simulated pressure changes in multilayer, multicomponent wrap systems when transitioning from rest to standing
The objective of this paper was to investigate the pressure applied to the lower leg by multilayer, multicomponent wrap systems, in different positions
The stretch profiles of five multilayer, multicomponent wrap systems were tested, three 2-layer and two 4-layer systems. These were quantified in the laboratory using a tensile testing device. The circumference of the lower leg was measured on healthy participants in three locations (ankle, B1 level, and calf) in three different postures (rest, dorsiflexion, and standing).
The largest changes in circumference were used to simulate the pressure changes under the multilayer, multicomponent products using Laplace's Law. While the pressure differences were large for the zinc plaster product, pressure changes ranged from 5–10mmHg for the other, more elastic products. Additionally, it was noted that the leg decreased in circumference at the B1 level and calf for the majority of participants when transitioning from sitting to standing. This decrease in size results in a decrease in bandage tension and applied pressure.
These results show that the sub-bandage pressure is not significantly affected by changes in posture when used as intended, within the therapeutic range.
Multilayer, multicomponent wrap systems are commonly used to apply compression to the limb increasing venous return and reducing oedema. The amount of pressure applied by a compression wrap is easily manipulated by wrapping the system more tightly or more loosely. For example, by pulling the wrap more tightly, the tension in the fabric increases and results in a larger applied force. The qualitative labels ‘more tightly’ and ‘more loosely’ are quantified as extension (engineering strain),1 which is computed as the change in length divided by the original length:
(1) Extension = ( new length − original length ) / ( original length )
The extension is usually reported as a per cent, such that a 100% extension would equate to a doubling in length. The relationship between tension and extension differs between products. Systems that are conventionally described as ‘stiff’ have a high resistance to stretching, and tension changes rapidly with small changes in extension.2 Systems that are thought of as being more ‘elastic’ have a lower resistance to stretching, and tension changes more gradually over a range of extension.2
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