PRESSURE SORES: CAUSATION AND COST, BIOMECHANIfSS AND PREVENTION M. T . M A N L E Y , P h .D . (B io en g .), B.Sc.* F I S I O T E R A P I E SEPTEMBER 197s IN T R O D U C T IO N : P R E S S U R E SO R ES T h e lo a d b e a rin g sk e le ta l sy ste m a n d th e v ita l o rg a n s o f th e b o d y a re is o la te d a n d p ro te c te d f r o m th e e x te rn a l e n v ir o n m e n t b y a c o n tin u o u s la y e r o f sk in a n d s u b c u ta n e o u s tissu e . In c o n se q u e n c e w h e n we sta n d , s it o r lie, th e a re a s o f sk in w h ic h a r e in c o n ta c t w ith th e s u p p o rtin g s u rfa c e a re su b je c te d to b o th n o r m a l a n d ta n g e n tia l fo rc e c o m p o n e n ts o f th e b o d y w eight. T h o s e fo rces c o m p re ss a n d d e fo rm th e la y e rs o f s o ft tis su e th r o u g h w h ich th e y a ct, a n d such d e f o rm a tio n m a y in te r f e r e w ith th e c u ta n e o u s c a p illa ry b lo o d su p p ly , w h ic h , if m a in ta in e d , lea d s to tis su e d e a th a n d th e f o r m a tio n o f a p re s s u re so re . I t is th u s a p p a r e n t th a t m a n is n o t d e sig n e d to re m a in im m o b ile f o r long p e rio d s o f tim e . H is n a tu r a l re a c tio n to im p o s e d im m o b ility is to r a n d o m ly m a k e sm a ll a d ju s tm e n ts in p o s tu re o r p o s itio n w h e th e r he is a w a k e o r a slee p , th e “f id g e tin g ” b e in g p a r tly s tim u la te d b y the fe e lin g o f d is c o m fo rt c au sed b y lo c a lis e d tis su e isc h a e m ia . U n f o r tu n a te ly th e c h ro n ic a lly ill, th e a ged, a n d th e im m o b ilis e d h a v e lo st th is p ro te c tiv e m e c h a n ism , a n d th e s e p a tie n ts a re m o s t lia b le to su ffe r fro m p re s s u re sores. T r a d itio n a lly , th e p r e v e n tio n o f p re s s u re so re s h a s b e e n c o n s id e re d as a n u rs in g p r o b le m a n d th e p re se n c e o f so re s as a m a n if e s ta tio n o f in a d e q u a te n u rs in g care. H o w e v e r, th e in c re a s in g n u m b e rs o f im m o b ilis e d a n d h a n d ic a p p e d p a tie n ts w o rld w id e h a v e f o c u s e d m o re a tte n tio n o n th e p ro b le m a n d it is n o w a c c e p te d t h a t so m e o f th e fa c to rs in p re s s u re so re a e tio lo g y a re in a d e q u a te ly u n d e rs to o d . B a sic re s e a rc h is b e in g c a r r ie d o u t w o rld w id e in to the effects o n s o ft tis su e p h y s io lo g y o f m e c h a n ic a l stress, in a d e q u a te n u tr it io n , c h e m ic a l i r r ita n ts , a n d m o is tu re . In a d d itio n , d ev ices to p r e v e n t so re s d e v e lo p in g in the c h ro n ic p a tie n t a re b e in g d e v e lo p e d . T h is p a p e r d e sc rib e s th e b io m e c h a n ic s o f p re ssu re so re s in th e sittin g a n d b e d -b o u n d p a tie n t a n d d iscu sses so m e o f th e te c h n iq u e s w h ic h a re n o w a v a ila b le f o r so re p re v e n tio n . \ IN C ID E N C E T h e in c id e n c e o f p re s s u re so re s in th e p a tie n t c o m ­ m u n ity h a s o n ly b e e n in v e s tig a te d re la tiv e ly re c e n tly a n d i n f o r m a tio n is still so m e w h a t sc a n t. D a ta c u rre n tly a v a ila b le in c lu d e s th e re su lts o f d e fin itiv e su rv e y s c o n ­ d u c te d in a la rg e h o s p ita l p o p u la tio n in C a p e T o w n (M a n le y 1978), in th e t o ta l p a ti e n t c o m m u n ity in G la sg o w (B a rb e n e l a al. 1977) a n d in th e t o ta l p o p u la ­ t io n o f th e c o u n ty o f A a r h u s in D e n m a r k (P e te rs e n a n d B ittm a n 1971). I t w as sh o w n b y a ll th r e e su rv e y s th a t th e o v e ra ll in c id e n c e o f p a tie n ts w ith p re s s u re so re s is a b o u t 9% o f th e to ta l p a tie n t p o p u la tio n , a lth o u g h th e in c id e n c e in c re a s e s sig n ific a n tly w ith in c re a s e in p a tie n t age. I n C a p e T o w n , f o r e x a m p le , a b o u t 20% o f th e p a tie n ts s u rv e y e d w e re o v e r r e tir in g a g e a n d th is 2 0 % h a d a b o u t 50%, o f t h e p re s s u re so re s fo u n d . T h e G la s ­ gow s u rv e y p ro d u c e d th e m o s t d r a m a tic a g e re la te d d a ta , as in th e to ta l p a tie n t c o m m u n ity o f t h a t c ity (h o sp ita l p a tie n ts p lu s h o m e b a s e d p a tie n ts ) 65% o f th e p a tie n ts su rv e y e d w e re o v e r r e tir in g age, a n d th e s e p a tie n ts * S e n io r L e c tu re r, D e p a r tm e n t o f B io m e d ic a l E n g in e e r ­ ing, U n iv e rs ity o f C a p e T o w n . c o n tr ib u te d 83% o f th e p re s s u re so re s re c o rd e d . Oth fa c to rs fo u n d to p re d is p o s e to p re s s u re sores \y»er in c o n tin e n c e , im m o b ility a n d u n c o n sc io u s n e s s. H ow ev/ 6 a ll re su lts sh o w ed th a t th e stro n g e st sin g le p re d ic t, f a c to r w as age. A n in te re s tin g re s u lt w h ic h emerooH f r o m th e C a p e T o w n su rv e y w as th e d is p a r ity in nre- o rig in a l le n g th , a lth o u g h th e re c o v e ry p ro c e ss does not o c c u r in s ta n ta n e o u s ly , a n d th e o r ig in a l le n g th m a y n ot be r e g a in e d f o r so m e h o u rs. O n c e th e sp e c im e n h as re tu r n e d to its o rig in a l resting d im e n s io n s th e e x p e rim e n ta l p r o c e d u r e c a n a g a in be re p e a te d . H o w e v e r, th e f o r c e /s tr a in c u rv e n o w o b ta in e d is sh o w n b y c u rv e B in F ig . 1. T h is c u rv e show s th at R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) first lo a d in g cycle h a s a p p a r e n tly g iv e n th e sp e c im e n th6 te r c o m p lia n c e , a n d a n in c re a s e d d e f o rm a tio n can be o b se rv e d a t each ste p in th e se c o n d lo a d in g n cedure U n lo a d in g a n d th e n re lo a d in g o n a th ir d c ; w in a g a in p r o d u c e a n a p p a r e n t c h a n g e in ° c h a n ic al c h a ra c te ris tic s (c u rv e C ) b u t th e r e a f te r th e 171611„ e x h ib its s ta b le c h a ra c te ris tic s a n d is sa id to be tlS!.c o n d itio n e d (D a ly 1966, F in l a y 1970, S ta rk e 1971). ^ L a b o r a to r y s tu d ie s lik e th e s e h a v e c le a rly sh o w n th a t t h e m ag n itu d e o f s o ft tis s u e d e f o rm a tio n d e p e n d s n o t n'v o n m a g n itu d e o f th e a p p lie d lo a d , b u t also non tim e o f a p p lic a tio n a n d t h e re p e titiv e n a tu r e o f “he lo ad in g cycle. S u ch re s u lts h a v e o b v io u s c lin ica l implications. . F in a lly , a n u n d e r s ta n d in g o f p re s s u re is c h a e m ia d e ­ m ands th a t th e lo a d in g p ro file s a p p lie d to s o ft tis su e during sittin g , ly in g , o r w a lk in g m u s t a lso b e stu d ied . \Vhen we lie, sit, o r s ta n d o u r b o d y w e ig h t is n o t evenly d is tr ib u te d a c ro ss th e a r e a o f sk in in c o n ta c t wjth th e s u p p o r t su rfa c e . T h e b o d y is n o t a rig id structure, a n d th e r e f o r e th e f o r c e a p p lie d a t th e b o d y / su p p o rt in te rfa c e in o n e a r e a w ill d iffe r f r o m th e tr e e a p p lie d a t th e in te rfa c e a t a n a d jo in in g a re a . In engineering te rm s th e c ritic a l m e a s u re is n o t sim p ly the m a g n itu d e o f a p p lie d fo rc e b u t th e r a ti o o f th is force to th e s u rfa c e a r e a o v e r w h ic h it acts. T h is ratio is k n o w n as th e stre ss a n d is a m e a s u re m e n t o f force in te n sity . I n th e c lin ic a l w o rld , s tre ss is u su a lly loosely re fe r r e d to as “ p r e s s u re ” a n d r e fe re n c e is m a d e to the p re s s u re b e tw e e n a s u b je c t a n d s u p p o r t su rfa c e . “In terfa ce p r e s s u r e ” is u s u a lly m e a s u re d a n d sp ecified in m illim etres o f m e r c u r y (m m H g ) a n d th is c o m m o n u sa g e vvill be a d h e re d to in th is a rtic le . I t is g e n e ra lly a c c e p te d that sores c a n b e p re v e n te d if t h e in te rfa c e p re s s u re a t a b o n y p ro m in e n c e is less th a n m e a n c a p illa r y b lo o d pressure (30 to 40 m m H g ), as u n d e r th is c o n d itio n cap illa ry b lo o d flow is m a in ta in e d a n d n o t a rre s te d b y the a p p lie d load. P R E V E N T IO N O F SO R E S THE R E C U M B E N T P A T IE N T T h e p ro je c te d a r e a o f s u p p o r t o f a s u p in e p a tie n t w hen d iv id e d b y h is b o d y w e ig h t y ie ld s a n a v e ra g e pressure o f a r o u n d 20 m m H g , w h ic h is w ell b e lo w m e a n c a p illa ry b lo o d p re s s u re (30 to 40 m m H g ). T h u s , if a p a tie n t is e v e n ly s u p p o r te d o v e r th e c o m p le te p o s te r io r of th e b o d y , p re s s u re so re s w ill n o t o c c u r. T h e sim p le st le th o d o f a c h ie v in g a w h o le b o d y s u p p o r t s i tu a tio n is “flo a t” th e b o d y in a s u ita b le fluid, a n d so m e su c c ess­ ful p re v e n tio n d e v ic es u s e th is flo ta tio n p r in c ip le . O th e r a p p ro a c h e s u se sh a p e d e la s tic fo a m to re m o v e lo a d s fro m b o n y p ro m in e n c e s , o r h ig h c o m p lia n c e e la stic fo a m to e q u a lis e s u p p o r t p re ssu re s. M e c h a n ic a l d ev ices w h ic h c o m p e n sa te f o r th e p a tie n t’s in h e r e n t lack o f m o b ility a n d s p o n ta n e o u s m o v e m e n t b y s h iftin g th e body w e ig h t a t re g u la r in te rv a ls c a n a lso b e u se d w ith success. Liquid Su pport (F lotation ) B eds P r o b a b ly th e s im p le s t f o r m o f liq u id s u p p o r t system is th e “ w a te r f lo ta tio n b e d ” w h ic h c o n sists o f a tu b filled w ith w a rm w a te r, th e s u rfa c e o f w h ic h is c o v e re d w ith a n e x tre m e ly lo o se fittin g sh e e t o f s y n th e tic r u b b e r o r v in y l. B e ca u se o f th e lo o se n ess o f th e sh e e t th e p a tie n t lite r a lly floats in th e w a te r a n d is s u p p o r te d b y h y d ro s ta tic p re s s u re a lo n e . H o w e v e r, if th e w a te r s u rfa c e is c o v e re d b y a tig h t sh e e t o r m e m b ra n e , th e p a ti e n t is su p p o rte d b y a c o m b in a tio n o f h y d r o s ta tic p re s s u re a n d m e m b ra n e te n s io n . M e m b ra n e te n s io n s u p p o r t is k n o w n as “h a m m o c k in g ” , a n d is a p o te n tia l p r o b le m in all ty p es o f flu id s u p p o r t system s, as th e s o ft tissu e s a re th e n su b je c te d to b o th s h e a r fo rc e s a n d in c re a s e d sEpTEMBER 1978 P H Y S I O T H E R A P Y 5 Fluid Support F ig . 2 in te rfa c e p re ssu re s. C o rre c t h y d r o s ta tic s u p p o r t a n d th e in c o rre c t m e m b ra n e te n s io n s u p p o r t a re sh o w n s c h e m a tic a lly in F ig . 2. A n i n h e re n t d isa d v a n ta g e o f th e w a te r f lo ta tio n sys­ te m is th e u n n a tu r a l p o s tu r e a d o p te d b y th e p a tie n t; flo atin g in a th r e e - q u a r te r s u b m e rg e d p o s itio n w ith h ip s a n d k nees flexed a n d fa c e ju st a b o v e th e su rfa ce . I n a d d itio n , th e b o d y is o n ly m a r g in a lly sta b le in th e w a te r a n d n u rs in g o p e r a tio n s a r e diffic u lt o n th e u n ­ s ta b le p la tf o r m o ffe re d b y th e w a te r su rfa c e . A d e v e lo p m e n t o f th e w a te r b e d first d e s c rib e d b y R e sw ic k (1972) is k n o w n as th e “ R a n c h o flo ta tio n b e d ” o r “ m u d b e d ” in w h ic h th e c o n ta in in g tu b is filled w ith o ilw e ll d rillin g m u d . A g a in th e su rfa c e o f th e s u p p o r tin g fluid is c o v e re d w ith a n e x tre m e ly lo o se fittin g v in y l s h e e t a n d th e p a tj e n t is s u p p o r te d b y h y d ro s ta tic p re ssu re . O ilw e ll d rillin g m u d h a s a d e n s ity a p p ro x im a te ly tw ice th a t o f w a te r a n d th e r e f o r e the b o d y o n ly sin k s h a lf as f a r in to th e s u p p o r tin g m e d iu m . T h e g r e a te r d e n s ity a n d v isc o sity o f m u d c o m p a re d to w a te r e n su re s t h a t s ta b ility is m a rk e d ly im p ro v e d a n d th a t th e p a tie n t floats in a m o re c o m fo rta b le p o s itio n . F ig. 3 c o m p a re th e “ flo a tin g ” p o s itio n o f p a tie n ts in b o th w a te r a n d m u d beds. O n e o f th e p ra c tic a l p ro b le m s w h ic h a ris e s in th e u se o f liq u id s u p p o r t b e d s is th e w e ig h t o f th e b e d o n c e it h a s b e e n filled w ith th e s u p p o r tin g fluid. F o r e x a m p le , a m u d b e d w h ic h c o n ta in s a b o u t 250 litre s o f m u d w e ig h s in excess o f 500 kg. I n a d d itio n , th e te m p e ra tu r e o f th e s u p p o rtin g liq u id m u s t b e c a re fu lly c o n tro lle d to e n s u re t h a t th e p a ti e n t is n o t h e a te d o r cooled. A ir Su pp ort System s T w o m a jo r ty p e s o f a ir s u p p o r t system s, k n o w n as h ig h a ir lo ss a n d low a ir loss b e d s, h a v e b e e n d ev elo p ed . T h e h ig h a ir loss b e d w as d e v e lo p e d p r i m a r i ly f o r th e t r e a tm e n t o f m a jo r b u m in ju rie s a n d th e p a ti e n t is s u p p o rte d b y a h ig h v o lu m e flow o f te m p e ra tu r e c o n ­ tr o lle d a i r a t low p re ssu re . T h e a i r is p a s s e d in to th e b a se o f a coffin sh a p e d b o x w h ic h c o n ta in s th e p a tie n t, R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) 6 F I S I O T E R A P I E SEPTEMBER 1978 WATER BED MUD BED a n d as th e a ir e x its to th e a tm o s p h e re , th e p a tie n t ’s b o d y is lifte d c le a r o f all s u p p o r tin g s u rfa c e s a n d “h o v e r s ” in th e box. T h e sy ste m h a s so m e a p p lic a tio n in p re s s u re s o re p re v e n tio n b u t is u n p o p u l a r w ith p a tie n ts , n o is y a n d diffic u lt to m a n a g e . T h e low a ir loss b e d (S cales 1976) w a s d e sig n e d sp e c ifica lly f o r p re v e n tio n o f p re s s u re n e c ro sis . T h e b e d is c o n s tru c te d o f 21 a ir sacs f a b ric a te d f r o m a m ic r o p o r o u s p o ly u r e th a n e c o a te d n y lo n f a b r i c w h ic h is p e rm e a b le to w a te r v a p o u r b u t w h ic h is im p e rm e a b le to a ir. M o is tu r e c o lle c tin g b e tw e e n th e p a ti e n t ’s b o d y s u rfa c e a n d th e sa c p e rm e a te s th e m e m b r a n e in to th e a ir sp a c e , th e v o lu m e flow o f a i r t h r o u g h e a c h sa c a n d th e m o is tu r e re m o v a l f r o m th e p a ti e n t’s s k in s u rfa c e b e in g c o n tro lle d b y a sy ste m o f o u tle t v a lv e s. B o d y w e ig h t is s u p p o r te d b y th e 21 sacs, th e p r e s s u re in e ac h sa c b e in g a d ju s te d to s u it a p a r tic u la r a r e a o f th e p a tie n t’s a n a to m y . T y p ic a l p re ssu re s a re : h e a d , tru n k , a n d s e a t g r o u p o f sacs — 20 m m H g ; th ig h — 10 m m H g ; c a lf a n d fo o t — 6 m m H g . F in a lly a q u a s i-flu id b e d “ th e F lu id is e d S a n d B e d ” , r e q u ir e s b r ie f c o n s id e r a tio n (S te w a rt 1976). T h e b e d c o n sists o f a b o x o r tr a y fu ll o f fine sa n d , th e b a s e o f th e t r a y b e in g c o n s tru c te d o f a steel m ic r o p o r e m esh . In o p e r a tio n a p a tie n t is p la c e d o n a sa n d s u r f a c e a n d a ir is p a sse d fro m a b lo w e r in to th e b a s e o f th e tr a y to g e n e ra te a “ q u ic k s a n d ” effect. T h e p a ti e n t sin k s slo w ly in to th e s a n d a n d w h e n a s u ita b le b o d y c o n to u r h a s b e e n f o r m e d th e s u p p lie d a i r is sw itc h e d off, a n d th e p a tie n t is s u p p o r te d b y a s u rfa c e w h ic h is in in tim a te c o n ta c t w ith th e b o d y . T h e in te rfa c e p re s s u re s o b ta in e d b y th is m e th o d h a v e n o t b e e n p u b lis h e d , b u t th e sa n d b e d is s a id to b e v e ry su c c essfu l in p re v e n tin g sores. D y n a m ic S u p p ort Su rfaces T h e flu id s u p p o r t b e d s d e s c rib e d a b o v e a tte m p t to a c h ie v e an a c c e p ta b le s ta tic r e d is tr ib u tio n o f p re s s u re a n d th u s a llo w th e p a tie n t to lie in o n e p o s i tio n fo r lo n g p e r io d s o f tim e . D y n a m ic s u p p o r t s u rfa c e s r e ­ lie v e p re s s u re is c h a e m ia b y c o n s ta n t a d ju s tm e n ts in th e p o s tu re o f th e p a tie n t, a n d th u s a tte m p ts to re p la c e th e n o rm a l p h y s io lo g ic a l “ f id g e tin g ” re s p o n s e to im ­ p o se d im m o b ility . I n th e i r s im p le s t f o r m th e y a r e a s ta n d a r d b e d a n d m a ttre s s fitte d o n to a “ r o c k e r ” a r r a n g e ­ m e n t, b u t su c h tu r n in g b e d s a re u n p o p u la r a n d o f little benefit. T h e m o re a c c e p ta b le ty p e o f dynam ic s u p p o r t s u rfa c e is th e so -c alled “ r ip p le m a ttre s s”, v a r ia tio n s o f w h ic h can n o w b e o b ta n ie d f r o m several m a n u fa c tu re rs . T h e r ip p le m a ttre s s c o n sists o f a m ulti- c e llu la r o r m u lti tu b e a ir m a ttre s s, a b o u t 75 m m thick, th e tu b e s b e in g p ro g re s s iv e ly in fla te d a n d d e flated with a ir to p ro d u c e a r ip p le effect. R ip p le m a ttre s se s are re la tiv e ly in e x p e n siv e , s im p le to use, a n d o fte n ex­ tre m e ly effe c tiv e in p re v e n tin g sores. T H E S IT T IN G P A T IE N T I t h a s b e en sh o w n th a t th e h ig h e s t in te rfa c e pressures e n c o u n te re d w h ile s ittin g o c c u r b e tw ee n th e support s u r f a c e a n d th e isc h ia l tu b e ro s itie s , a n d p e a k pressures in th e o r d e r o f 300 m g H g h a v e b e e n m e a s u re d in this a r e a fro m s u b je c ts s ittin g o n a w o o d e n c h a ir (M anley el al. 1977). E v e n w h e n a p a tie n t is s ittin g o n a soft fo a m c u s h io n , c a p illa r y o c c lu s io n m a y still o c c u r as the in te rfa c e p re s s u re s b e n e a th th e tu b e r o s itie s is o ften in excess o f 100 m m H g . A d d itio n a lly , if th e r e is a ten d e n cy f o r th e b u tto c k s to slip f o r w a r d in th e c h a ir, frictio n iL o r s h e a r fo rc e s w ill f u r t h e r d e f o rm th e lo a d e d tissues a n d c a u se f u r th e r o c c lu s io n o f c a p illa rie s . N u m e r o u s m e th o d s h a v e b e e n p ro p o s e d fo r preventing so re s in s ittin g p a tie n ts a n d m a n y d iffe re n t types of se a t c u sh io n s o r p a d s a re n o w a v a ila b le . C u sh io n s de­ sig n e d f o r lo n g -te rm s ittin g c a n b e su b d iv id e d into p a ssiv e o r a c tiv e c a te g o rie s, th e p a ssiv e c u sh io n attem pt­ ing to r e d is tr ib u te s ta tic a lly th e “ n a tu r a l ” interface p re ssu re s w h ile th e a c tiv e c u sh io n p ro v id e s a constantly c h a n g in g p a ti e n t/s u p p o r t c o n ta c t a r e a a n d th u s cyclic tis su e lo a d in g . C u s h io n s w h ic h fa ll in to th e passive c a te g o ry in c lu d in g f lo ta tio n p a d s w h ic h m a y b e filled w ith a ir , w a te r, o r s ilic o n e flu id ; b e a n b ags consisting o f c lo th e n v e lo p e s filled w ith d ry m a c ro s p h e re s (usually p o ly s ty re n e b e a d s ); gel p a d s o f silic o n e o r vinyl gel e n c lo se d in a n im p e rv io u s e n v e lo p e o r in closed cell fo a m ; e la s tic fo a m c u sh io n s o f la te x o r polyurethane; v isc o -e la s tic fo a m c u sh io n s w h ic h a tte m p t to provide g r e a te r s ta b ility th a n th e p u re ly e la s tic v a rie ty ; and c u s to m -m a d e v a c u u m f o rm e d se a ts w h ic h a tte m p t to p ro v id e th e m a x im u m p a tie n t s u p p o r t c o n ta c t area. A c tiv e c u s h io n s a re u s u a lly o f th e rip p le se a t o r alter­ n a tin g p re s s u re p a d v a rie ty , in w h ic h a i r o r a support flu id is p u m p e d th ro u g h lin k e d c h a m b e rs o r pipes to R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) S E P T E M B E R 1978 P H Y S I O T H E R A P Y 7 move bod v w e i g h t c \ d i c a l k f r o m o n e a r e a l o a n o t h e r Active d e u c e s p r e v e n t t h e p r o l o n g e d a p p l i c a t i o n ot excessive i n t e r l a c e p r e s s u r e r a t h e r t h a n r e d u c e t h e magni t ude o f p e a k l o a d s o n i h e s i t t i n g a r e a . Both p a s s i v e a n d a c t i v e sv s t e r ns h a v e a c h i e v e d s o m e success in p r e v e n t i n g s o r e s . P r o b l e m s w i t h s u p p o r t devices in t h e p a s s i v e c a t e g o r y i n c l u d e t h e i n s t a b i l i t y , floppiness a n d w e i g h t o f l l ui d a n d gel p a d s , t h e h e a t retention p r o p e r t i e s ol b e a n b a g s , a n d t h e e x p e n s e a n d ma i nt e n a n c e r e q u i r e m e n t s o f v a c u u m t o r m e d seat s. In the a c t i v e c a l e g o r v . r i p p l e i v p e s e a t s a r e c u m b e r ­ some a n d r e q u i r e e x t e n s i v e m o d i f i c a t i o n t o a w h e e l ­ chair ( i n c l u d i n g t h e a d d i t i o n o f a p o w e i s u p p K ): as lhe\ c a n b e e x p e n s i v e lo buv a n d m a i n t a i n t hev a r c not suitable f o r t h e m a j o r i t y o f w h e e l c h a i r us e r s . T h e s i m p l e s t a n d l eas t e x p e n s i v e s i l l i n g s u p p o r t s u r ­ faces a r e c o n s t r u c t e d f r o m e l a s t i c t o r v i s e o - c l a s l i c ) foam, a n d a l a r g e v a i i e t v ot p r e s s u r e rcl i el c u s h i o n s const ruct ed f r o m l o a m m a t e r i a l s a r e c o m m e r c i a l l y a v a i l ­ able. Mo s t o f t h e s e c u s h i o n s a t t e m p t to p r o v i d e a s i t t i n g surface w h i c h c o n f o r m s t o t h e p a t i e n t ' s b o d \ s h a p e , b u t Ifjonflicting d e s i g n r e q u i r e m e n t s m e a n t h a t h i g h f o a m ' fbnsilN a n d r e s i l i e n c e a r e r e q u i r e d t o p r e v e n t b o t t o m ­ i n g o u t " o f t he c u s h i o n , a n d a l ow f o a m d e n s i t y is r equi red to p r o v i d e b o t h a " s o f t f e e l " a n d g o o d c o n - JformabiIit\ C o n s e q u e n t l y . m a n y l o a m c u s h i o n s a r e l a mi na t e d f r o m t w o o r m o r e m a t e r i a l s o f d i f f e r e n t densi ti es t o pr ov i de a c o m p r o m i s e s o l u t i o n : t hi s is n o t totally e f f e c t i v e in p r e v e n t i n g sor es . A f o a m c u s h i o n w h i c h h a s -shown Use It to b e very effective in b o t h p r e v e n t i n g a n d h e a l i n g s i t t i n g s o r e s is the P a r a e a i e c u s h i o n d e v e l o p e d at ( o n r a d i e H o s p i t a l ( M a n l e y c/ al. 1977). I h e c u s h i o n is c o n s t r u c t e d I r o m e x p a n d e d p o l y u r e t h a n e e l a s t i c l o a m o f h i g h d e n s i t v w h i c h p r e v e n t s " b o t t o m i n g o u t " ol t h e p e l v i s o n t o t he w h e e l c h a i r s e a l a n d a c u t - o u t u n d e r t h e i sc hi i e n s u r e s l ha l m o s t o f t h e l o a d w h i c h w o u l d h a v e b e e n c a r r i e d bv t h e l u b e r o s i l i e s is n o w c a r r i e d o n t h e " t r o c h a n t e r i c shel l* a n d i h i g h s ( Fi g . 4). In e a r l y d e s i g n s o f i he P a r a c a r e c u s h i o n t h e c u t - o u t w a s c u s t o m - f i l l e d l o t he a n a t o m y o f t h e i n d i v i d u a l p a t i e n t to e n s u r e l h a i l o a d i n g w a s c o m p l e t e ! v r e m o v e d f r o m t h e t u b e r o s i t i e s , b u t s u b s e q u e n t l y it h a s b e e n s h o w n t h a t t h e i s c hi i c a n safel y w' i i h s t a n d a n i n i e r l a c e p r e s s u r e o f a b o u t 4 0 m m H g . A b l o c k o f l o w d e n s i i v l o a m is n o w l i l t ed i n i o t h e c u t ­ o u t so t h a t i h e t u b e r o s i t i e s c a r r y a s m a l l p r o p o r t i o n o f b ody w e i g h t , a n d t h i s w e i g h t s h a r i n g b e t w e e n ( he t r o c h a n i e r i c s h e l f a n d i sc hi i h a s a l l o w e d t h e f i t t i ng p r o c e d u r e t o b e s i m p l i f i e d s o t h a i onl y t h r e e s i / c s ot c u s h i o n c u t - o u t n o w n e e d b e c o n s t r u c t e d . A c o m p l e t e P a r a c a r e c u s h i o n is s h o w n in Fi g. 5. I he r a i s e d f r o n t p o r t i o n o f t h e c u s h i o n s t r u c t u r e e n s u r e s t h a t t h e m a x i m u m p o s s i b l e l o a d is t r a n s f e r r e d t o i he " s a f e ” w e i g h t b e a r i n g a r e a o f t h e i h i g h s . w h i l e i he c u r v e d b a s e fills t h e s a g in t h e w h e e l c h a i r h a m m o c k se a l a n d p r e v e n t s d i s t o r t i o n o f i h e c u t - o u l d i m e n s i o n s o n i h e u p p e r s u r f a c e . The c o m p l e t e c u s h i o n is l i n e d wi i h a I w o - w a v s t r e t c h f a b r i c w h i c h p r e v e n t s a b r a s i v e w e a r o f t he l o a m a n d r e d u c e s s o i l i n g ol t h e c u s h i o n . In a d d i t i o n to t h e P a r a c a r e c u s h i o n , p a t i e n i s at ( o n r a d i e a r e a l s o s u p p l i e d w i t h a s h a p e d b a c k r e s t w h i c h is d e s i g n e d t o e n s u r e a n o - l o a d c o n d i t i o n o n t h e s a c r u m , c o c c y x . a n d v e r t e b r a l p r o c e s s e s . T h e b a c k r e s t a l s o e n s u r e s t ha t t h e p a i i c n t ' s i schi i a r e p o s i t i o n e d I in. 4 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) 8 F i c . 5 c o r r e c t l y in t he c u s h i o n c u t - o u t , i m p r o v e s p a t i c n l p o s t u r e in ( he c h a i r a n d p r o v i d e s l a t e r a l s t a b i l i t y f o r p a t i e n t s w i t h a h i g h l evel o f s p i n a l l e s i o n . L u m b a r s u p p o r t is a l s o p r o v i d e d l o r i m p r o v e d p a t i e n t c o m f o r t , a n d t h e b a c k r e s t is a g a i n c o v e r e d in t wo - wa y s t r e t c h f a b r i c . L o c a t i o n to t h e w h e e l c h a i r is by e l a s t i c t a p e s , o v e r t h e w h e e l c h a i r h a n d l e s a n d by " V e l c r o ” t a p e s to (he r e a r o f t h e c u s h i o n c o v e r . A c o m p l e t e P a r a c a r e s e a t i n g s y s t e m is s h o w n in F i g . 6. C O N C L U S I O N : R E H A B I L I T A T I O N A N D C O S T B E N E F I T S I h e r a p i d l y g r o w i n g w o r l d w i d e p o p u l a t i o n o f h a n d i ­ c a p p e d ani l h e l p l e s s p e o p l e h a s l ed to a n e s c a l a t i o n in h e a l t h c a r e cos t s. T h e U n i t e d . States, f o r e x a m p l e , n o w s p e n d s a b o u t 18".. o f its g r o s s n a t i o n a l p r o d u c t o n h e a l t h c a r e , a n d t he a v e r a g e cos t to s o c i e t y f o r e a c h p a t i e n t t r e a t e d h a s a p p r o x i m a t e ! ; , t r e b l e d in t h e last e i g h t y e a r s ( K e n e d i 1977). T h e r e a r c n o w c l e a r i n d i ­ c a t i o n s . p a r t i c u l a r l y in t h e " c a r i n g ” s o c i e t i e s , t ha t t he f i n a n c i a l a n d m a n p o w e r d e m a n d s o f t h e h e a l t h c a r e s e r v i c e s ma y very s o o n o u t r u n t he r e s o u r c e s t ha t c a n b e a l l o c a t e d to t h e m . In c o n s e q u e n c e , h e a l t h e a r e m u s t b e c o m e m o r e cos t e f f e c t i ve , a n d p a t i e n t s m u s t be r e h a b i l i t a t e d a n d r e i n t e g r a t e d i n t o s oc i e t y at t h e e a r l i e s t p o s s i b l e s t a g e in t h e i r t r e a t m e n t . It is e v i d e n t t hat p r e s s u r e s o r e s , w h e t h e r d u e t o p r o l o n g e d b e d r e s t o r to p r o l o n g e d s i t t i n g c a n onl y d e l a y t h e r e h a b i l i t a t i o n p r o ­ cess. a n d a c t i v e s t e p s t a k e n al t h e e a r l i e s t o p p o r t u n i t y t o p r e v e n t s o r e s m u s t i n c r e a s e t h e cos t e f f e c t i v e n e s s of m e d i c a l car e. R e f c r e n c c s I B a r b c n c l . J. (' . . J o r d a n . M. M a n d N i c o l . S. ( 1977) : " T h e i n c i d e n c e o f p r e s s u r e s o r e s " . L a n c e t , 2. 548. 2. D a l y . C . H. ( 1966) : " T h e b i o m e c h a n i c a l c h a r a c t c r i s - li cs o f h u m a n s k i n " P h . D . T h e s i s . U n i v . S t r a t h c l y d e . Ci l a s gow. 3. F i n l a y . J. 13. ( 1970) : " B i o d y n a m i c s t u d i e s o f h u m a n s k i n " P h . D . T h e s i s . U n i \ . S t r a t h c l y d e . G l a s g o w . 4. F u n g . V-C . ( 1972) : " S t r e s s - s t r a i n - h i s t o r y r e l a t i o n s o f sof t t i s s u e in s i m p l e e l o n g a t i o n " in B i o m e c h a n i c s : its f o u n d a t i o n s a n d o b j e c t i v e s , ed. F u n g ; publ . P r e n t i c e - H a l l . 5. G i b s o n . T. . f i a r b c n e l . J. ( & F. va ns . J. H. ( 1976): " B i o m e c h a n i c a l ( o n c e p t s a n d E f f e c t s " in B e d s o r e I' it:. <> B i o m e c h a n i c s , ed. R. M. K e n e d i a n d J. C. owden; M a c m i l l a n Press. 6. K e n e d i . R. M. ( 1977) : " E n g i n e e r i n g C o s t s and Be ne f i t s in H e a l t h C a r e " in Pr o c . I n t e r n a t i o n a l C o n f e r e n c e in B i o e n g i n e e r i n g , C a p e T o w n . A p r ® 1977. , 7. K e n e d i . R. M. . G i b s o n . 7 . . E v l / i s . J. H. a nd B a r b e n e l . J. C. ( 1975) : " T i s s u e m e c h a n i c s " . Phvs. M e d . Biol. 20. 699 - 717. X. M a n l e y . M. T. ( 1978) : " P r e s s u r e sor e s , c o n t r i b u t o r y f a c t o r s a n d c o s t s " S. A fi. M e d . J.. 53. 217 - 222. 9. M a n l e y . M. T. . W a k e f i e l d . E. & K e y . A. G . (1977): " T h e p r e v e n t i o n a n d t r e a t m e n t o f p r e s s u r e s o r e s in t h e s i t t i n g p a r a p l e g i c " .V. A jr. M e d . J.. 52. 771. 10. P e t e r s e n . N. C. a n d B i t t m a n . S. ( 1971) : " E p i d e m i o ­ l ogy o f p r e s s u r e s o r e s " . S ta n d . J. I ’ln.si. Rccunsir. Surf;.. 5. 62. II R e s w i c k . J. ( 1972) : " R a n c h o F l o t a t i o n B e d " in T h e Eff ect o f P r e s s u r e o n S o f t T i s s u e s . N a t i o n a l A c a ­ d e m y o f S c i e n c e s . W a s h i n g t o n . 12. Sc a l e s . J. T . ( 1976) : " A i r s u p p o r t s y s t e m s f o r the p r e v e n t i o n o f b e d s o r e s " in B e d s o r e B i o m e c h a n i c s , ed. R. M. K e n e d i a n d J. C o w d e n ; M a c m i l l a n Press. 13. S t a r k . H. ( 1971) : " T h e s u r g i c a l l i mi t s o f e x t e n s i o n a n d c o m p r e s s i o n o f h u m a n s k i n " . P h . D . Thesi s . U n i v . S t r a t h c l y d e . G l a s g o w . 14. S t e w a r t . 1. M ( 1976) : " S a n d Be d N u r s i n g " in B e d s o r e B i o m e c h a n i c s , ed. R. M. K e n e d i a n d J. C o w d e n : M a c m i l l a n Press. F I S I O T E R A P I E SEPTEMBER 1978 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. )