Technology and product reviews T E C H N O L O G Y U P D A T E :


Defining ‘active’ pressure redistribution


This paper will explore the design principles of ‘active’ (alternating) support surfaces, discuss how specific characteristics might influence physiology, pathophysiology and the prevention of pressure ulcers, and introduce the rationale for a standardised performance measurement.


Authors (Clockwise from top left): Lyn Phillips, Richard


Goossens, Makoto Takahashi, Michael Clark


INTRODUCTION Pressure ulcer prevention guidelines routinely include the prescription of regular patient repositioning, and a pressure-redistributing surface for beds and chairs[1]


, the . However, selecting a


support surface from the rapidly expanding list of available options is difficult. Reliable information from high quality clinical trials is scant[2]


References


1. EPUAP-NPUAP Pressure ulcer prevention guideline. Available


at: www.epuap.org. (Accessed on 21 August, 2012)


2. Vanderwee K, Grypdonck M, Defloor T. Alternating pressure air mattresses as prevention


for pressure ulcers: A literature review. Int J Nurs Studies. 2008; 45: 784–801


3. NPUAP. Support Surfaces


Standarization Initiative. Terms and Definitions related to


support surfaces. 2007: Available at: www.npuap.org/NPUAP_S3I_ TD.pdf (Accessed on 21 August, 2012)


4. Clark M. Understanding support surfaces. Wounds International. 2011; 2(3): 17–19


5. Giganti F, Ficca G, Gori S et al. Body movements during night sleep and their relationship with sleep stages are further modified in very old subjects. Brain Res Bull. 2008; 75(1): 66–69


terminology for reporting support-surface performance is confusing and the measurements used to describe product performance are not, as yet, standardised. Nevertheless, an informed prescription


requires a basic understanding of support surface functionality and an appreciation that surfaces are not generic with respect to clinical performance.


WHAT IS ‘ACTIVE’ THERAPY? Since 2007, the National Pressure Ulcer Advisory Panel (NPUAP)[3]


Pressure Ulcer Advisory Panel (EPUAP)[1]


unless the patient is repositioned, the pressure remains constant and may still be sufficient to occlude the circulation to the tissue. This modality has been covered in a previous issue of this publication[4] further


and will, therefore, not be discussed


Active surface These are powered devices designed to periodically redistribute pressure by repeatedly loading and unloading the pressure beneath the body[3]


. Unloading,


, and, more recently, the European , has


classified support surfaces into one of two functional categories, as determined by the primary method of pressure redistribution[Fig 1].


Reactive surface Included here for clarity, these range from simple foam, gel and non-powered, air-filled surfaces, through to powered low-air-loss and air-fluidised beds. Measurable performance characteristics include immersion into, and envelopment by, the supporting materials mentioned above[3]


.


By increasing the surface area that supports the body, the applied pressure is lowered, however,


52 Wounds International Vol 3 | Issue 3 | ©Wounds International 2012


or pressure removal, is typically achieved through the alternate inflation and deflation of a series of air-filled cells, giving rise to the more traditional description of ‘alternating therapy’ or ‘alternating pressure air mattress’. Unlike reactive surfaces, cyclical pressure redistribution continues even in the absence of patient movement, although the degree of off-loading varies by device.


Why ‘active’? The purpose, form and function of active pressure redistribution can best be described by first revisiting standard physiology. Essentially, as terrestrial mammals, human beings are naturally exposed to periods of relatively high, non-uniform, pressure. Even so, most do not develop tissue injury thanks to complex and highly successful, protective physiological mechanisms, including spontaneous movement; a subconscious behavioural response, which redistributes


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