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A number of factors contribute to the development of a pressure sore. After a period of prolonged sitting the tissues expreiancing the greatest pressure will exibit decreased perfusion of oxygen and carbon dioxide, as well as elevated temperatures. reduced perfusions and increased temperature can lead to tissue necrosis, and the development of a pressure sore. The effectiveness of the iPUPc at releiving pressure in the seating area, and consequently increasing prefusion and reducing temperature elevation was examined
Subjects were fitted with sensors to measure tissue perfusion, pressure distribution, and skin temperature. they then sat in a chair for one hour, performing a pressure relief every 20 min. they then sat in the chair with the iPUPc running, providing a pressure relief automatically every 10 min. Individuals with parpalegia, tetrapalegia, and healthy controls were tested.
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Interface Pressure using iPUPc
A number of risk factors have been cited for pressure ulcer formation, of which pressure concentrated over bony prominences is thought to be the single most important etiologic factor. Prolonged high pressure results in local tissue ischemia, which is associated with local perfusion failure of nutritive capillaries and leads to tissue necrosis Furthermore, sustained elevated pressure leads to impaired lymphatic and venous circulation in the compressed tissue, resulting in an accumulation of toxic intracellular materials. Short term loading produces elastic deformation and rapid elastic recovery, whereas long-term loading requires significant time for complete tissue recovery.
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Setup
Two Xsensor (Xsensor Technology Corporation, Calgary,
Canada) pressure-mapping mats with 36 x 36 cells were
secured over the surface of the backrest and the seat
before the subject transferred into the wheelchair to
record the interface pressure on backrest and the seat
with a sampling frequency of 1 Hz.
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Results
Representative results of the alternate and normal plus pushup sitting protocols. Data are from 1 subject in the paraplegic group. (A) Average pressure (AP) and TCA on the posterior portion of the seat cushion during a trial of the alternate protocol. (B) Average pressure and TCA on the posterior portion of the seat cushion during a trial of the normal plus pushup protocol. NOTE. The horizontal lines indicate the average value over the entire 1-hour sitting trial.
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Tissue Perfusion Near Bony Landmarks While Seating
Prolonged high pressure results in local tissue ischemia, which is associated with local perfusion failure of nutritive capillaries and leads to
tissue necrosis (4,17–19). Furthermore, sustained elevated pressure leads to impaired lymphatic and venous circulation in the compressed tissue, resulting in an accumulation of toxic intracellular materials (20). Short term
loading produces elastic deformation and rapid elastic recovery, whereas long-term loading requires significant time for complete tissue recovery.
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Tissue Perfusion Levels
Representative results of tissue perfusion and AP for dynamic and wheelchair pushup sitting protocols.
Data are from 1 subject in the paraplegic group. (A)
Tissue perfusion at IT and AP on posterior seat during a
trial of Dynamic protocol. (B) Tissue perfusion and AP on
posterior seat during a trial of wheelchair pushup
protocol.
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Recovery Time
Average tissue perfusion recovery time during interface pressure decrease and average tissue perfusion deterioration time during interface pressure increase for control, paraplegic, and tetraplegic groups. The average
pushup time achieved by the paraplegic group is also given in A as a comparison to perfusion recovery time. (A) Perfusion recovery time during interface pressure decrease compared with pushup time. (B) Perfusion deterioration time during interface pressure increase.
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Temperature Elevation During Prolonged Sitting
Skin Temperature is an indicator of tissue inflamation and eventually tissue necrosis. Prolonged periods of time sitting without pressure relief can result in increased temperature in the tissues,and current pressure relief protocols do not allow for significant temperature restoration. The iPUPc was evaluated to determine how effectively it reduced temperature elevation during pressure relief.
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Results
representitive data recorded from the sitting area during seating trials. Alternate trials were performed with the seat automatically changing positions every 10 minutes. Normal+ Pushup data was collected with the subject performing a pressure relief pushup every 20 min. The Alternate protocol allowed for greater temperature reduction during pressurerelief, and an overall reduction of temperature buildup over the courseof the experiment
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