DECEMBER 1980 P H Y S I O T H E R A P Y 97 AIRWAY P RESS U RE CHANGES DURING “ BAG S Q U E E Z I N G ” I. H A C K f , A . K A T Z ,f C . E A L E S , B.Sc. (P h y s io th e ra p y ) ( W itw a te r s r a n d ) t S U M M A R Y P ressure da ta d u rin g c o n tr o lle d v e n tila tio n on a v e n ­ tilator, "b a g g in g ” a n d slo w “bagging” are re v ie w ed . T h e te c h n iq u e f o r e ffe c tiv e “b a g g in g ” is suggested. IN T R O D U C T IO N A stu d y w as d o n e to c la rify a n d u n d e r s ta n d th e v ery w idely u se d p h y s io th e r a p e u tic te c h n iq u e o f “ bag - s q u e e z in g ” . I t w as a tte m p te d to e s ta b lish th e re le v a n c e o f th e r a te o f p re s s u re c h a n g e w h ic h o c c u rs d u rin g “ b a g -sq u e e z in g ” c o m p a re d w ith th e tid a l v e n tila tio n o f a p a tie n t o n a v e n tila to r. F r o m a p h y sio lo g ic a l p o in t o f ~~'fiew, th e fo llo w in g w e re a ls o in v e s tig a te d : r e la tiv e d a n ­ g e r s , ' in d ic a tio n s a n d c o n tra -in d ic a tio n s a n d th e a p p r o ­ p ria te te c h n iq u e o f u sin g th e se lf-in fla tin g bag. T h e A m b u -b a g is a se lf-in fla tin g , m a n u a lly o p e ra te d b a g c o n sistin g o f a n in n e r lin in g o f n a tu r a l ru b b e r a n d a n o u te r c o v e rin g o f N e o p re n e . T h e o u te r lin in g allo w s f o r th e a u to m a tic re tu r n o f th e b a g to its o rig in a l sh a p e a f te r c o m p re ssio n . A tta c h e d to th e b a g is a o n e -w ay n o n -re b re a th in g v a lv e . O n c o m p re s s io n o f th e b a g , a ir is d ire c te d th ro u g h th e v a lv e to th e p a tie n t a n d d u rin g e x p ira tio n a n d re le a s e o f th e b a g th e e x p ire d a ir is allo w e d o u t in to th e a tm o s p h e re w ith v e ry little , if a n y , re sista n c e th u s p re v e n tin g re b re a th in g in to th e bag. T h e v o lu m e d e liv e re d b y m o s t b a g s is u p to 1,2 to 1,3 litre s w h e n c o m p re ss e d m a x im a lly . O n n o rm a l c o m p re s ­ sion, th e b a g y ield s a b o u t 6 00 - 8 00 m l. I f re q u ire d , a p o sitiv e e n d e x p ir a to r y p re s s u re (P E E P ) v a lv e c a n be a tta c h e d to th e b a g , w h ic h c a n m a in ta in a P E E P o f up to 10 cm w a te r. A ir, w h ic h m a y b e e n ric h e d w ith o xygen, pa sse s fro m th e b a g th ro u g h th e n o n - r e tu m v a lv e v ia th e c o n n e c to r t u b in g to th e i n tu b a te d p a tie n t (e ith e r e n d o tra c h e a l tu b e o r tra c h e o s to m y ). “ B a g -sq u e e z in g ” is a m a n u a l te c h n iq u e f o r h y p e r in ­ fla tio n o f th e lu n g s w h ic h is u se d e x te n siv e ly in in te n ­ sive c a re u n its b y p h y s io th e ra p is ts . I t is u se d in c o n ­ ju n c tio n w ith c h e s t m a n ip u la tio n s (v ib ra tio n s, sh a k in g , rib sp rin g in g ) a n d su c tio n in g . rfL jn d ication s fo r the use o f an A m bu-bag '^ R e s u s c ita tio n In c o m b in a tio n w ith a sim p le fa c e m ask f o r a n y f o r m o f r e s p ira to ry f a ilu re u n til a d e fin itiv e a irw a y h a s b e e n e sta b lish e d . O n c e th e e n d o tr a c h e a l o r tr a c h e o s to m y tu b e is in situ , “ b a g g in g ” m a y b e c o n tin u e d — th e b a g n o w b e in g a tta c h e d d ire c tly to th e in tu b a tio n tu b e . F o r th e in e x p e rie n c e d o p e r a to r , m o u th to m o u th re su sc ita - ion is p ro b a b ly a s a fe r m e th o d . In a b ility to c ough “ B a g -sq u e ez in g ” is u se d in c o n ju n c tio n w ith s u c tio n ­ ing to s tim u la te a c o u g h reflex. A f te r “ b a g g in g ” th e e x p ira to ry p h a s e o f r e s p ira tio n is a ssiste d w ith m a n u a l c o m p re ss io n o r v ib ra tio n o f th e th o r a x in o r d e r to g a in a m o re fo rc e fu l e x p ira tio n a n d to a id re m o v a l o f s e c re ­ tio n s . F o r e x a m p le , w h e n a p a tie n t o n e le c tiv e p e n - to th a l loses h is c o u g h reflex, “ b a g g in g ” a n d v ib ra tio n s a re u se d d u rin g tr e a tm e n t to s im u la te a c o u g h a n d m o v e th e se c re tio n s. * S tu d e n t p r o je c t p re s e n te d f o r B.Sc. P h y s io th e ra p y IV . S u b -D e p a rtm e n t o f P h y s io th e ra p y , U n iv e rs ity o f th e W itw a te rs ra n d (1980). t B.Sc. P h y s io th e ra p y IV 1980. ^ P a rt-tim e le c tu re r, S u b -D e p a rtm e n t o f P h y s io th e ra p y , U n iv e rs ity o f th e W itw a te rs ra n d . O P S O M M IN G D a ta o m tr e n t d r u k k e g e d u re n d e g e k o n tro le e rd e v e n ti- lasie te r w y l p a sie n te m e t ’n v e n tila to r b e h a n d e l w o rd , “ba gging” en sta d ig e ' bagging” w o r d nagegaan. D ie teg n ie k v ir d o e ltr e ffe n d e “b a g g in g ” w o r d v o o rg iste l. R e in fla tio n R e in fla tio n o f m ic ro a te le c ta tic a re a s a f te r su c tio n in g . C o u g h p r o d u c tio n P r o d u c tio n o f a n efficient c o u g h w h e re th e lu n g se c re tio n s a re m o re diffic u lt to re m o v e b e c a u se o f in ­ tu b a tio n . L o o s e n in g se c retio n s “ B a g -sq u e e z in g ” m a y m o v e th e w a rm sa lin e w h ic h is in je c te d in to th e e n d o tr a c h e a l o r tra c h e o s to m y tu b e in to m o re d is ta l a irw ay s a n d a r o u n d th e a lv e o la r w alls, th u s lo o se n in g se c re tio n s . L im ite d re sp ira to ry e ffo r t “ B a g g in g ” e n su re s p e rio d ic h y p e rin fla tio n o f th e lungs, as in s p o n ta n e o u s d e ep b re a th in g . V e n tila to r m a lfu n c tio n o r w h e n v e n tila to rs are being clea n ed T h e p a tie n t is a rtific ia lly v e n tila te d u sin g th e self- in fla tin g bag. C on traind ications fo r th e use o f the A m bu-bag P a tie n ts w ith p o o r c ir c u la tio n a n d lo w cardiac o u tp u t A n u n d e s ira b le d e p re ss io n o f th e c a r d ia c o u tp u t m a y re s u lt b e c a u s e o f th e p o sitiv e p re s s u re g e n e ra te d in th e th o ra x . P n e u m o th o r a x , in te rc o sta l d rain o r b ro n c h o p le u r a l fis tu la In th e p a tie n t w ith a n u n d ra in e d p n e u m o th o r a x , a c la m p e d in te rc o s ta l d r a in o r in th e case o f a b r o n c h o ­ p le u ra l fistu la , b e c a u s e t h e in c re a s e d a irw a y p re s s u re co u ld le a d to a te n s io n p n e u m o th o ra x . L o w h a e m o g lo b in In p a tie n ts w ith a low h a e m o g lo b in level w h o d o n o t h a v e a su fficient o x y g e n -c a rry in g c a p a c ity o f th e b lo o d . H y p e rin fla tio n o f th e lu n g s in a n a tte m p t to im p ro v e b lo o d o x y g e n a tio n w o u ld se rv e n o u se fu l p u rp o se . B ro n c h o sp a sm I n se v e re b ro n c h o s p a s m , th e v e ry h ig h in tr a th o r a c ic p re ssu re s c re a te d , c o u ld in c re a s e th e b ro n c h o s p a s m . R E L A T IV E C O N T R A IN D IC A T IO N F O R T H E U S E O F A N A M B U B A G In p a tie n ts w ith m u ltip le rib fra c tu re s , w h e re “ b a g g in g ” c o u ld d islo d g e th e b o n e s a t th e f r a c tu r e s ite w ith re s u l­ ta n t p ie rc in g o f a lu n g . In th is case a su g g e ste d tid a l v o lu m e o f 600 - 8 00 m l s h o u ld b e u se d f o r “ b a g g in g ” . C om p lication s and D an gers P n e u m o th o r a x G e n e r a tio n o f v e ry h ig h in s p ira to ry p re ssu re s c o u ld re s u lt in th e r u p tu r e o f a lv e o li, e v e n in re la tiv e ly n o r ­ m al lu n g s. T h e p r o b a b ility o f c a u s in g a p n e u m o th o r a x is in c re a s e d in e m p h y s e m a to u s p a tie n ts , fo llo w in g m u l­ tip le rib fra c tu r e s o r a f te r s u b c la v ia n v e in c a th e te ris a - tio n (L ew is, 1978). H y p o te n s io n T h e h y p o te n s iv e p a tie n t a lr e a d y h a s a d e c re a s e d c a r ­ d ia c o u t p u t a n d th e c o m p e n s a to ry m e c h a n is m o f p e r i­ p h e ra l v e n o u s c o n s tric tio n in a n a tte m p t to d e c re a s e th e f u r t h e r d ro p in c a r d ia c o u t p u t d u rin g p o s itiv e p re s s u re b r e a th in g is in effe ctiv e. S e v e re h y p o te n s io n m a y th e n 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. ) 98 F I S I O T E R A P I E DESEMBER 1980 T A B L E 1. N u m e ric a l d a ta c a lc u la te d fro m g ra p h s. P re s s u re s in b ra c k e ts re p re s e n t P E E P v a lu e s fo r th o s e p a tie n ts . A v e ra g e n u m b e r o f d iv isio n s A v e ra g e n u m b e r d u rin g o f d iv isio n s V e n tila to r c o n tr o lle d d u rin g P ressure P a tie n t v e n tila tio n “bagging” (cm H , 0 ) A. 11,0 19,125 32 (8) B. 17,67 26,5 20 (5) C. 18,67 27,125 28 D. 19,1 33 28 (4) E. 25,25 33,5 28 (10) C a lcu la ted P ressure P ressure P erce n ta g e o f “ b a gging”R e p r e s e n te d d u rin g by one “bagging” g re a ter than d iv isio n c m (H iO ) v e n tila tio n 2,18 41,69 55,28 ( + 8 ) 37,50,85 22,5 ( + 5 ) 1,5 40,69 45,32 1,46 48,18 62,79 ( + 4 ) 20,680,71 23.79 (+ 1 0 ) H y p o x ia T h is c a n re s u lt in p a tie n ts w ith se v e re r e s p ira to ry fa ilu r e if th e o x y g e n flow is in a d e q u a te o r if “ b a g g in g ” is n o t c a rrie d o u t c o rre c tly a n d th e p a tie n t is u n d e r v e n ­ tila te d . A s a p re c a u tio n th e c a rd ia c m o n ito r sh o u ld b e u se d to w a r n t h e o p e r a to r o f th e p o ss ib le b r a d y c a rd ia w h ic h m a y o c c u r as a re s u lt o f t h e h y p o x ia . D e p re ss io n o f the re sp ira to ry drive O v e r-v e n tila tio n o f th e p a tie n t c a n re s u lt in th e b lo w ­ in g off o f c a rb o n d io x id e a n d d e p re ss io n o f th e re s p ira ­ to ry drive. M E T H O D S tu d ie s w e re c o n d u c te d o n five a d u lt p a tie n ts in th e in te n s iv e c a re u n its o f th e J o h a n n e s b u r g G e n e r a l H o s ­ p ita l. P a tie n ts w e re v e n tila te d o n a B e n n e t r e s p ira to r via a tra c h e o s to m y o r a n e n d o tra c h e a l tu b e . A p re ssu re tra n s d u c e r w as a tta c h e d to th e P o rte x c o n n e c tio n of th e p a ti e n t ’s c a th e te r m o u n t a n d th e n to a re c o rd e r w ith a n o sc illo sc o p e a n d tr a c e r fro m w h ic h g ra p h s o f p re s s u re c h a n g e s w e re o b ta in e d . A c o m p a ris o n c o u ld th e n be m a d e b e tw e e n th e p a ti e n t ’s r e s p ira tio n as c o n ­ tro lle d b y th e v e n tila to r a n d t h a t w h ic h w as o b ta in e d f ro m “ b a g -s q u e e z in g ” . P re s s u re c h a n g e s o f c o n tro lle d re s p ira tio n w e re re c o rd e d . (F ig. 1). tio n . A se lf-in fla tin g b a g w as th e n a tta c h e d to th e d istal e n d o f th e c a th e te r m o u n t a n d a se c o n d tra c in g w as re c o rd e d w h ilst t h e p a tie n t w as b e in g “ b a g g e d ” . ( F ig „ 2). \ T h e a p p r o p ria te P E E P v a lu e w as a p p lie d b y m e a n s o f a P E E P v a lv e a tta c h e d to th e b a g , as re q u ire d by th e p a tie n t. T h e te c h n iq u e s o f sq u e e z in g th e b ag in v o lv e d the o p e r a to r c o m p re ss in g th e b a g w ith b o th h a n d s , th e u ln a r b o rd e rs re s tin g o n th e b ed fo r s u p p o r t to m in i­ m is e m o v e m e n t a t th e tr a c h e o s to m y site. T h e b a g w as c o m p re ss e d w ith b o th h a n d s to give th e o p e r a to r som e id e a o f th e c o m p lia n c e o f th e lung. E a c h c o m p re ss io n a llo w e d fo r th e d e liv e ry o f a v o lu m e o f a ir sufficient to h y p e rin fla te th e lungs. T h e p a tie n t w as “ b a g g e d ” five to six tim e s w ith th e p a tie n t in th e s u p in e p o sitio n . I n itia lly , a s p iro m e te r w as a tta c h e d to th e b a g in an a tte m p t to m e a s u re th e v o lu m e o f gas d e liv e re d to th e p a tie n t. T h is , h o w e v e r, p ro v e d in a c c u ra te b e c a u s e w hen th e b a g w as a tta c h e d to th e o x y g e n , th e sp iro m e te r n e e d le m o v e d ro u n d c o n tin u o u s ly as a re s u lt o f th e o x y g e n flow. I t w as e s tim a te d th a t a v o lu m e o f 1,2 to 1,3 litre s o f gas w as d e liv e re d to th e p a tie n ts . F r o m th e p e a k p re ssu re s d u rin g c o n tro lle d re s p ira tio n th e m e a n p e a k p re s s u re w as c a lc u la te d b y a v e ra g in g th e n u m b e r o f d iv is io n s o n th e g r a p h p a p e r fro m th e b a se lin e to th e p e a k p r e s s u r e p o in t. T h e a v e ra g e n u m b e r o f d iv is io n s w e re th e n e q u a te d to th e m e a n p e a k p re s ­ s u r e (in cm H .O ). F ro m th is d a ta it w as p o ss ib le to c a l­ c u la te h o w m a n y c e n tim e tre s o f w a te r o n e d iv is io n 7 re p re s e n te d . T h is v a lu e w as th e n u sed to c a lc u la te t l i f ^ p r e s s u r e m e a s u re m e n ts d u rin g “ b a g g in g ” . A c o m p a ris o n w as th e n m a d e b e tw e e n th e p re ssu re s o f c o n tro lle d r e s p ira tio n a n d “ b a g g in g ” in te rm s o f “ p e rc e n ta g e g re a te r t h a n ” . (T a b le 1). F in a lly , as a c o m p a ris o n , slow g e n tle “ b a g g in g ” to d e liv e r a tid a l v o lu m e (600 - 8 00 m l) w as in c lu d e d a n d p re s s u re tra c in g s w e re re c o rd e d (Fig. 3). F ig. 2. P ressure ch an ges during “baggin g” . I i T E C l t :: r t ' l ' 1I I r j ; x f t : i"t T;i::i:l£l;;:iEi:;;t;''n F ig . 3. Pressure changes during slow , gentle “bag­ g in g” (a m uch flatter graph with a m uch sm aller peak pressure). 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. ) DECEMBER 1980 R E S U L T S A lth o u g h e a c h p a tie n t ’s p a tt e r n o f v e n tila tio n d i f ­ fe re d d e p e n d in g o n th e m a c h in e s e ttin g a n d th e p a ti e n t ’s c o n d itio n , th e g ra p h tra c e d o u t d u rin g “ b a g ­ g in g ” w as fo u n d to b e re la tiv e ly u n if o r m fo r all p a tie n ts te s te d a n d v a rie d slig h tly d e p e n d in g o n th e d e g re e a n d ra te o f c o m p re s s io n o f th e bag. F ro m T a b le 1, it c a n be se e n t h a t in e a c h c ase th e re w as a n in c re a s e d p e rc e n ta g e p re s s u re w h e n “ b a g g in g ” w as in stitu te d . T h e r a te o f in c re a s e in p re ssu re , d e te rm in e d b y th e g ra d ie n t o f th e g ra p h ( th a t is, c h a n g e in Y -a x is o r p r e s ­ su re , d iv id e d b y c h a n g e in X -a x is o r tim e ), w as h ig h e r d u rin g “ b a g g in g ” , r e a c h in g a h ig h e r p e a k p re ssu re . (T a b le 2). O n c e th e p e a k p re s s u re w as re a c h e d , th e re w as a n in itia l g ra d u a l lin e a r d e c lin e in p re ssu re , fo l­ low ed b y a v e ry ste e p , a lm o s t v e rtic a l d e c lin e in p re s ­ su re to th e re stin g level. ' T a b le 2. G ra d ie n ts o f g ra p h s o f p a tie n ts d u rin g v e n tila tio n a n d “ b a g g in g ” . G r a d ie n t o f G r a d ie n t o f P a tie n t V e n tila tio n “B a g g in g ” A. 0,34 1,55 B. 0,87 2,15 C. 0,83 1,64 D . 0,68 1,61 E . 0.92 1,03 D IS C U S S IO N T h e h ig h r a te o f in c re a s e in p re s s u re re s u lts fro m a g re a te r v o lu m e o f gas b e in g d e liv e re d to th e p a ti e n t a t a fa s te r ra te d u rin g “ b a g g in g ” as o p p o se d to th a t o f tid a l v e n tila tio n . T h is ra p id in c re a s e in p re s s u re re su lts in a n in c re a s e d flow in th e c e n tr a l a irw a y s w h ic h is tra n s m itte d to th e m o re d is ta l a irw ay s. W ith th is in ­ cre a sin g flow, tu rb u le n c e in a p p ro x im a te ly th e first 6 o r 7 g e n e ra tio n s o f th e b ro n c h ia l tre e re su lts , c au sin g m o v e m e n t o f a n y se c re tio n s p re s e n t in th e s e airw ays. B e ca u se a la rg e r v o lu m e o f g a s is d e liv e re d a t a h ig h e r p re ssu re , gas is a lso fo rc e d b e y o n d th e se c re tio n s so t h a t a h igh e x p ir a to r y flow ra te , a ssiste d b y v ib ra tio n s, will m o v e se c re tio n s m o re c e n tra lly . I n a d d itio n , b e tte r ^ ^ v e n t i l a t i o n o f u n o b s tru c te d alv e o li c o u ld re s u lt in col- ,t r i l a t e r a l airflow to a lv e o li w h ic h a re filled w ith secre- tio n s o r to c o lla p se d a lv e o li w h o se te r m in a l b ro n c h i a re o b stru c te d . T h e in itia l slow d e c lin e in p re ssu re , o n c e th e p e a k p re ssu re h a s b e en re a c h e d (F ig. 2), c o u ld p o ss ib ly b e a ttrib u te d to le a k a g e o f e x p ire d a ir b a c k t h r o u g h th e v a lv e in to th e bag. B e a rin g th is in m in d , slow g e n tle “ b a g g in g ” w h ic h h a s a lo n g e r p la te a u (F ig. 3), w ill re su lt in g re a te r r e b re a th in g . T h e re fo re , it c a n b e c o n ­ c lu d e d th a t th e slo w e r th e b a g is re le a s e d th e g re a te r th e a m o u n t o f r e b re a th in g (L o e h n in g e t a l., 1964). A la rg e in s p ira to ry v o lu m e w ith a h ig h p re s s u re c h a n g e fo llo w ed b y a h ig h e x p ira to ry flow r a te is c o m ­ p a ra b le to th e r e q u ire m e n ts f o r a n effe c tiv e c o u g h . A n effective c o u g h d e p e n d s o n th e v e lo c ity o f th e gas in th e airw ays, w h e re v e lo c ity (v) is e q u a l to flow r a te (V) d ivided b y c ro ss-sec tio n a l a r e a (A ): v = V /A . A sm a ll c ro ss-sec tio n a l a re a a n d a h ig h flow r a te w ill p ro d u c e 99 a n e ffe c tiv e c o u g h (M a c k le m , 1974). “ B a g g in g ” is a n a tte m p t to s im u la te th is b y p ro d u c in g a h ig h e x p ira to ry flow r a te in th e tra c h e o b ro n c h ia l tree . I n th e case o f P a tie n t E , th e r e is n o t as m a rk e d a c h a n g e in p e a k p re s s u re a n d in g ra d ie n t in “ b a g g in g ” as c o m p a re d to c o n tro lle d v e n tila tio n . T h is c an b e a t t r i ­ b u te d to th e f a c t t h a t th is p a tie n t h a d se v e re b r o n c h o ­ sp a sm a n d th e r e f o r e h ig h a irw a y re sista n c e . A re la tiv e ly h ig h p e a k p re s s u re a n d g r a d ie n t w e re o b ta in e d e v en d u rin g c o n tro lle d v e n tila tio n . Su ggested T ech n iq u e fo r A m bu-bagging F r o m th e re su lts , th e a u th o rs su g g e st t h a t th e fo llo w ­ ing te c h n iq u e o f “ b a g g in g ” b e u s e d to c a u s e h y p e rin fla ­ tio n o f a lv e o li, c o lla te ra l a irflow a n d m o v e m e n t o f s e c re tio n s . I n o rd e r to d e liv e r a m a x im u m v o lu m e o f gas to th e p a tie n t, th e b a g s h o u ld b e h e ld in b o th h a n d s, w ith th e u ln a r b o rd e rs re s tin g o n a firm su rfa c e , e.g. th e bed, a n d th e n c o m p re ss e d s m o o th ly a n d m a x im a lly w ith b o th h a n d s . T h is te c h n iq u e e n a b le s th e o p e r a to r to ju d g e c o m p lia n c e , c o m p re ss t h e b a g a c c o rd in g ly a n d th e re b y m in im is e th e p o ss ib ility o f c a u s in g a p n e u m o ­ th o ra x . A firm s u rfa c e is su g g e ste d to s u p p o r t th e h a n d s , to m in im is e th e m o v e m e n t o f th e b a g d u rin g c o m p re ss io n a n d th u s p re v e n tin g p u llin g a t th e t r a ­ c h e o s to m y site a n d d is c o m fo rt fo r th e p a tie n t. G e n tle “ b a g -sq u e e z in g ” w ith o n e h a n d w ill o n ly re s u lt in d e li­ v e ry o f a tid a l v o lu m e a n d so th e d e sire d effects w ill n o t b e a c h ie v e d . I f g e n tle “ b a g -sq u e e z in g ” is u se d , th e b a g s h o u ld b e c o m p re ss e d a n d re le a s e d q u ic k ly to m in i­ m is e re b re a th in g . “ B a g g in g ” s h o u ld b e u se d in c o n ju n c tio n w ith s u c ­ tio n in g . P r io r to s u c tio n in g th e p a tie n t sh o u ld be flushed w ith 100% o x y g e n in o rd e r to p r e v e n t th e h y p o x ia w h ic h m a y re s u lt d u rin g th e p ro c e d u re . T h e p a tie n t is “ b a g g e d ” five o r six tim e s in b e tw e e n th e su c tio n in g p ro c e d u re s . T h e “ b a g g in g ” is c o m b in e d w ith v ib ra tio n s w h ic h a re c o m m e n c e d as so o n as th e o p e r a ­ to r h a s c o m p le te d sq u e e z in g th e b a g . T h e v ib ra tio n s are c o n tin u e d th r o u g h o u t th e e x p ir a to r y p h a s e in o r d e r to re in f o r c e th e h ig h e x p ira to ry flow r a te in m o v in g s e c re ­ tio n s fro m th e p e rip h e ry to th e c e n tra l a irw ay s. I f the p a tie n t is c o n sc io u s , h e is e n c o u ra g e d to c o u g h w h ile th e su c tio n c a th e te r is b e in g w ith d ra w n . A f te r s u c tio n ­ ing, th e p a tie n t is “ b a g g e d ” a g a in a b o u t th r e e tim e s to re in fla te a n y a te le c ta tic a re a s w h ic h m a y h a v e o c c u rre d . C O N C L U S IO N “ B a g -sq u e e z in g ” p e rfo rm e d as su g g e ste d is th e m o s t e ffective m e a n s o f s im u la tin g a c o u g h . A la rg e in s p ira ­ to ry v o lu m e is d e liv e re d a t a h ig h p re s s u re fo rc in g a ir b e y o n d se c re tio n s . T h is is fo llo w e d by a h ig h e x p ira to ry flow r a te p ro p e llin g se c re tio n s to th e p ro x im a l a irw ay s w h e re th e y m a y b e su c tio n e d o r c o u g h e d u p a n d ex­ p e c to ra te d . R eferen ces L ew is, S. (1978): P h y s io th e ra p y in th e in te n s iv e th e ra p y u n it. N u r s in g T im e s , 74: 534-537. L o e h n in g , R . W ., D a v is, G ., S a fa r, P. (1964): R e b r e a th ­ ing w ith “ n o n re b re a th in g ” valves. A n e s th e sio lo g y , 25: 854-856. M a c k le m , P . T . (1974). P h y s io lo g y o f c o u g h . A n n a ls o f O to lo g y , 83: 761-768. P H Y S I O T H E R A P Y 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. )