66 F I S I O T E R A P I E SEPTEMBER 1980 Last, R. J. (1972). A natom y: Regional and applied. 5th Ed. C hurchill L ivingstone. E dinburgh and L ondon. Liebow, A . A., H ales, M . R. and Lindskog, G . E. (1949). E n larg e m en t o f th e b ro n ch ial arteries and their anastom oses w ith th e pulm onary arteries in bronchiectasis. A m . J. P ath., 25, 211. N agaishi, C. (1972). F u n ctio n al anatom y and histology o f the lung. 1st E d. B altim ore an d L ondon, U niversity P a rk Press. M eyer, B. J. (1976). D ie fisiologiese basis van genees- kunde. H .A .U .M . C ape Town. P um p, K. K . (1972). D istribu tion of th e bron chial arteries in the h u m an lungs. C hest, 62, 4 4 7 -4 5 1 . Shedd, D . P ., A lley, R . D . an d L indskog, G . E. (1951). O bservations on th e hem adynam ics o f b ro n ch ial-p u l­ m onary vascular com m unications. J. Thorac. Surg., 22, 537 - 548. T obin, C. E. (1952). T he bronchial arteries and their connections w ith o ther vessels in th e hu m an lung. Surg. G ynec. an d O bst., 95, 741 - 750. T obin, C. E. (1966), A rterio-venous shunts in th e p e ri­ p h eral pulm onary circulation in th e h u m an lung. Thorax, 21, 197 - 204. West, J. B. (1974). R espiratory physiology — th e essen­ tials. Blackwell Scientific P u b licatio n , O xford, L on­ don, E d inburgh, M elbourne. W ood, D . A . and M iller, M . (1937/8). T h e ro le of the dual pulm onary circulation in various pathologic conditions of the lungs. ]. Thorac. Surg., 7, 649 - 670. A cknow ledgem ent P rof. A. D. M alan, D e p a rtm e n t o f A natom y, U niver­ sity o f Stellenbosch. ASCULTATION OF THE CHEST D R. S T E P H E N C. M O R R IS O N ,* M .A ., M.B., B .C hir., M .R .C .P. SU M M A R Y T h e stethoscope a n d its use are described. A s current classification o f breath sounds, voice sou n d s an d a d v e n ­ titious sounds is presented, and its use in diagnosis outlined. F inally, the value o f auscultation to the physio­ therapist is discussed. IN T R O D U C T IO N T h e invention o f the stethoscope by L aennec in 1818 was a m ajo r advance in m edicine; the instrum ent allow ed diagnosis and assessm ent of cardio-respiratory disorders to be carried o u t w ith precision not previously attainable, an d to this day th e stethoscope rem ains an indispensable p a rt o f th e physician’s arm am entarium . F o r physiotherapists, how ever, the situation is n o t so clear cut. A substantial p ro p o rtio n of physicians and surgeons view w ith deepest suspicion th e sight o f a physiotherapist auscultating a p a tie n t’s chest. In the eyes of these critics it verges on blasphem y fo r th e physio­ therapist to own a stethoscope, or to carry one ab o u t as a m a tte r o f routine. T h e opposite view point is held by m any m em bers o f the physiotherapy profession, believing au scu ltatio n to be very m uch their business, and a valuable source o f info rm atio n p ertin en t to the perform ance o f their w ork. I do n o t propose to enter into th e pros an d cons of this controversy. I consider it beyond dispute, how ever, th a t if the stethoscope is to be used by physiotherapists, it should be used correctly, w ith insight an d understanding. T his article is w ritten to help achieve this end. TH E S T E T H O S C O P E (G reek stethos, the chest; skopeein, to explore). T h ere are th ree com ponents o f the m odem steth o ­ scope. T hey are th e chest piece, th e tubing and the binaural. T h e chest piece may b e o f th e bell type, diaph ragm type, o r a com bination o f these two. T h e two are really variants o f the sam e principle — th a t o f a dam ped diaphragm system . T h e area of skin enclosed by the bell behave as a diaphragm , th e tautness of w hich m ay be varied b y the pressure applied. T h e firm ly applied * R espiratory C linic, G ro o te Schuur H ospital, C ape T o w a R eceived 16 July 1980. O PSO M M 1N G D ie steto sko o p en d ie geb ru ik daarvan w ord beskryf. ’n H uidige klassifikasie van asem halingsklanke, stem - hebbende kla n ke en b yko m en d e klanke w ord voorgestel, en die gebruik daarvan in diagnostiek w ord om skryf. T en slotte w o rd die waarde van ouskultasie vir die fisioterapeut bespreek. bell th erefore subtends an area o f ta u t skin which behaves in a sim ilar way to the diaphragm chest piece; it filters out low frequency sounds, allow ing the higher frequencies to com e through. I t should be rem em bered, though, th a t the volum e of sound is related to the area of the chest piece, so th at th e diaphragm chest piece, being larger, will in general p roduce a higher am plitude of sound than the firmly applied bell. In contrast, the softly applied bell subtends an area of lax skin which will have a m uch low er reso n an t frequency, favouring the transm ission of low frequency sounds. H e a rt sounds, and som e cardiac m urm urs, are in the low er frequency range (2 0 - 1 1 5 cycles/sec), so that cardiologists will usually prefer the softly applied f j , when auscultating th e heart. NL-*" Lung sounds, however, and especially abnorm al lung sounds, are in th e higher frequency range (200 - 2 000 cycles/sec), so th a t use of the diaphragm is generally preferable, although the firmly applied bell could be used. A dvantages of the diaphragm include the higher am plitude o f sound, as alread y m entioned, and the easier application over an uneven or bony chest cage, w here incom plete contact betw een skin and th e rim of the bell w ould result in com plete loss o f sound. T he firm ly applied bell m ay be useful on occasion; for exam ple, in confirm ing the presence o f fine adventitious sounds which can som etim es be generated artificially by m ovem ent o f the diaphragm on the skin surface. T he bell is also useful in children, for w hom the diaphragm m ay be inappropriately large, although p aediatric stethoscopes are available. T h e tubing is o f considerable im portance in the efficiency o f a stethoscope. Sound loss can result from the use of incorrect dim ensions or m aterials. T h e m ate­ rial should be firm, inert, reasonably thick and polished in its in tern al bore fo r m axim um transm ission. Loss of high frequencies can result if the volum e o f the system is too large o r if the diam eter o f the tubing is too fine. A good- com prom ise is T ygon tubing, as used in the 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. ) SEPTEMBER 1980 P H Y S I O T H E R A P Y 67 L ittm an stethoscope (L ittm an, 1961), w ith a lum en 3 mm in d iam eter and 35 cm in length fro m chest piece to the base o f the “ Y ” section. L onger tubes add nothing in convenience, and seriously im pair sound conduction. Som e physicians prefer a tw in-tubed in stru ­ m ent, rightly m aintaining th a t loss o f sound occurs at the “ Y ” section in single-tubed stethoscopes. T his bene­ fit o f the tw in-tubed instrum ent is p artly offset b y the necessarily larger volum e o f the system. Furtherm ore, twin tubes exhibit an annoying tendency to ru b together, producing extraneous sounds. H ence, the m ore com pact single-tubed instrum ent is preferable for general use. T he b inaural is th e final link in the chain betw een chest and ear, and is the source of m uch difficulty with auscultation. T h e ear piece should b e as large as pos­ sible; no sm aller than 12 m m and as large as 15 mm. T hey are intended to occlude the external auditory canals, not to invade them. F o r m ost individuals, the external auditory canal is directed ab o u t 20° anteriorly from its m eatus, and the b inaural should be adjusted " \ i t i l a com fortable fit is achieved. A firm spring tension fcs required to hold the binaural in place, and this will not be uncom fortable provided the earpieces are large enough. L eakage and loss of sound will re su lt if spring tension is inadequate. Prevention o f leaks is o f great im portance if the stethoscope is to be used efficiently. T h e chief sources o f leaks are the earpieces, the bell-diaphragm change­ over m echanism , and cracks in the diaphragm or tubing. A useful test of the acoustic seal of the w hole system is w ithdraw al o f the chest piece quickly from the pre- cordium , when a painful sensation should be produced a t the ear. L U N G SO U N D S In the m ost im p o rtan t discussion o f lung sounds since Laennec, Forgacs (1978) has placed their genesis and classification on a scientific and practical footing. T he term s he en um erates are unam biguous, and in general m ake no im plications a b r-it the source of sounds, except w here this has been clearly elucidated. These term s have been w idely adopted, and will be used throughout this article. O lder term s should now be abandoned. T he classification is sum m arised in Figure 1. Breath Sounds Breath Sounds N o rm a l Breath Sounds Lun g Sounds Voice Sounds Norm al Bronchophony Aegophony A d ven titio u s Sounds Fig. 1 Fig. 2 T he total cross-sectional area o f the airw ays becom es progressively larger fro m trachea to alveoli (F igure 2). H ence, if total air flow in the central an d peripheral airw ays is to be the sam e (as it m ust be), the velocity o f the airstream will be considerably higher in the central airways. T hus flow in the central airw ays will be m ore prone to turbulence, and hence th e generation o f sound. T h e source o f norm al breath sounds is now know n to be these central airways, i.e. th e trachea and larger bronchi. A stethoscope placed over the trachea will reveal b reath sounds com prising frequencies from 200 to 2 000 cycles/sec, and audible th ro u g h o u t m ost of th e v en tila­ tory cycle. In contrast, a stethoscope placed on the chest wall will dem onstrate the sound absorptive and acoustic filtering effects o f the lung tissue situated betw een the large, bronchi and the chest wall. T h e sound am plitude is m uch lower owing to absorption by th e lung; the frequency range is also lower, (from 200 to 600 cycles/ sec), because lung tissue behaves as a “ low pass” filter w hich selectively absorbs the higher frequencies. A con­ sequence of the lower am plitude is th a t b re a th sounds a re only audible when the flow rate is above about 0,75 litres/sec. T his still includes m ost o f inspiration, b u t only ab o u t one third of the longer expiratory phase (Figure 3). T h u s norm al b reath sounds are low fre­ quency, low am p litu d e sounds, heard during inspiration and the first third o f expiration. B ronchial breath sounds or bronchial breathing If the alveoli becom e filled w ith fluid ra th e r th a n air, there is relatively little loss of sound by absorption or filtration. T h e b re a th sounds h eard a t th e chest w ill will therefore resem ble those heard over the trachea, i.e. they will be greater in am plitude, higher in frequency, and audible over a longer p ro p o rtio n o f th e v entilatory cycle. T his is called bronchial breathing, an d is charac­ teristic of the sound heard over an area o f consolida­ tion, e.g. in lobar pneum onia. In certain individuals, and p articu larly in children, norm al b reath sounds m ay take on a slightly bronchial 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. ) 68 F I S I O T E R A P I E Flow, litres i sec Fig. 3 quality owing to the proxim ity of the trachea and chest wall. This occurs especially in the central inter-scapular area on the back, and is of little consequence provided it is rem em bered. A v arian t o f bron chial breathing is am phoric breathing w here lo w frequency breath sounds app ear selectively amplified, and the bronchial breathing has a hollow ring to it. T his type o f breath sound is n o t infrequently heard over a large cavity. R ed u ced or absent breath sounds B reath sounds m ay be reduced or absent w here the lung is separated from th e chest wall, either by air (as in pneum othorax) or by fluid (as in pleural effusion). T he two conditions are generally distinguishable on o th er grounds, such as percussion note. R educed breath sounds are also a featu re of em physem a, b u t will usually be accom panied by adventitious sounds in this condition. Localised redu ction in b reath sounds m ay im ply a totally obstructed lobar or segm ental bronchus. Voice Sounds N o rm a l V oice S ounds In the sam e way th a t breath sounds are atten u ated and filtered by air-filled lung tissue, so the sounds of phonated and w hispered speech, which originate in the larynx and m outh, are likewise atten u ated and filtered by the lung. Speech is therefore reduced to a low frequency m um ble in which words can n o t be distin­ guished, and w hispering is no t norm ally audible a t the chest wall. B ronchophony W here the lung betw een the central airw ays and the chest wall becom es fluid-filled as in consolidation, the higher frequency voice sounds are transm itted and w ords becom e distinguishable. T his is know n as bronchophony. W hispered speech, which is com posed entirely o f higher frequency sounds, becom es clearly transm itted to the chest wall, a sign know n as whispering pectoriloquy. SEPTEMBER 1980 T hese three signs (bronchial breathing, bronchophony and whispering pectoriloquy) form the triad of auscul­ tato ry signs of consolidation and all are the result of the sam e acoustic phenom enon. A c g o p h o n y A t th e upper bo rd er of a pleural effusion, where visceral and p arietal pleura interface with pleural fluid, there is a tendency for lower frequency sounds to be selectively atten u ated . Voice sounds are th erefo re tran s­ m itted w ith a high-pitched, nasal or b leating quality, and this is know n as aegophony. Adventitious Sounds C rackles C rackles are short, explosive, non-m usical sounds. T h eir genesis has been a subject of considerable cop^ fusion for m any years. T he m ost im p o rtan t single f « " || to rem em ber is that, except in the case o f the ve*r largest airways, the resistance offered by surface tension and viscosity of bronchial secretions is too high to allow “ bubb lin g ” of air through secretions. F o r practical purposes, we should try to assign crack 'es into one of three different subtypes as this differentiation may be m ade with relative ease on acoustic grounds. W hile some inferences m ay be draw n in regard to underlying pathology, such inferences should be m ade with caution, and alm ost never from auscultatory evidence alone. Fine, late respiratory crackles If an alveolus of the lung becom es closed during any p art of the b reath in g cycle, then during th e next inspi­ ration, a pressure g radient will build up trying to re-open the closed alveolus. T here will com e a p oint where the inspiratory force is strong enough to overcom e the com bined surface tension and elastic forces; at th a t point the alveolus will open abruptly, w ith rapid m ove­ m ent of air, thus equalising the air pressure betw een the alveolus and its conducting airway. T his rapid equalisa­ tion o f pressure is accom panied by a fine, high-pitched crackle, usually occurring late in inspiration. C rackles of this type are th erefore heard in situations characterised by alveolar closure during som e p art o f the ventilatory cycle. Such closure does not occur in tidal breathing in healthy young adults, b u t it m ay do so if F u n c tio /y ,, R esidual C apacity (FR C )* falls, or if pulm onary e la s v 6- recbil increases, either of these situations tending to bring alveoli nearer to collapse. E xam ples o f the form er are the atelectasis which follow s abdom inal surgery, and states of m uscular weakness such as m yasthenia gravis. E xam ples of increased elastic recoil w ould include fibrosing alveolitis, pneum oconioses (e.g. asbestosis) and interstitial pulm onary oedem a. It is w orth repeating th at tt’e crackles w hich occur in the latter condition derive from the effect of interstitial fluid on elastic recoil of the lung, and not from the presence of free fluid in the alveoli. In all these conditions, the alveoli nearest the closure will be those in th e lowest p a rt of the lung, being subject to the com pressive weight of the overlying lung tissue. T his fact may be dem onstrated, for exam ple in a p atien t w ith fibrosing alveolitis, by obser­ vation o f the effect of posture (head down, supine, prone, standing etc.) when the crackles will localise cach tim e to th e lowest zone. In sum m ary, fine, late- inspiratory crackles are heard in interstitial pulm onary disorders or in otherw ise norm al lungs when F R C is * volum e of air rem aining in the lungs at the end of a norm al breath. 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. ) SEPTEMBER 1980 P H Y S I O T H E R A P Y 69 reduced. N o t surprisingly, these crackles are unaffected by coughing, and do not occur on expiration. E arly inspiratory and expiratory cnicklcs T his kind of sound is com m only heard in patients with chronic airflow obstruction. T h e crackles arise from b rg e airways, are low pitched and rather scanty. T hey are thought to be due to in term itten t opening of lightly closed bronchi, and each crackle corresponds to the passage of a single bolus o f gas through the closed airway. T h e tendency for these airw ays to close may be related to structural changes know n to occur in chronic airflow obstruction, but this is incom pletely understood at the present time. N evertheless, crackles o f this type a re am ong the com m onest encountered in th e practice o f respiratory m edicine. T hey occur both on inspiration and on expiration, and are unaffected by coughing or posture. Siarse crackles related to bronchial secretionsD espite the foregoing, th ere rem ains a grpup of patients in whom unexpectorated secretions lie in the trachea and larger bronchi. T h e m ovem ent of air over and through these secretions gives rise to crackles o f the loudest and coarsest type, both on inspiration and on expiration. T hese crackles are m arkedly reduced after coughing or endotracheal suction. T heir presence corre­ lates with inability or unwillingness to cough rath er than with a specific disease and they occur in chronic bronchitis, bronchiectasis, pneum onia, tuberculosis, florid pu lm onary oedem a, or any condition giving rise to large volum es of intra-bronchial fluid. O ften these patients will be in a m oribund state, and this is the situation aptly portrayed in the lay term “ death ra ttle ” . W heeze W heezes are m usical sounds em anating from the lungs. T hey are heard on auscultation of the chest, bu t may also be audible w ithout a stethoscope. A lthough the precise m echanism s of wheeze p ro duction are com ­ plex, the principle is th at air flowing through narrow ed bronchi sets up vibrations in the walls of those bronchi. W heeze therefore occurs in conditions w here airways are obstructed, e.g. asthm a and chronic bronchitis. Only in large and medium -sized b ronchi is there sufficient air flow to generate wheeze, and the com m on belief th a t ■Nigh-pitched wheezes originate from the sm allest peri- M e r a l airways is pro b ab ly untrue. T h e pitch of a wheeze aepends m ore on the resonant frequency of the bronchial wall than the dim ensions of the bronchus. Because expiration is associated with com pression and fu rth er narrowing of in trath o racic airways, wheeze is usually more p rom inent during expiration; indeed a wheeze present only on inspiration strongly implies the presence of an extra-thoracic obstruction, e.g. in the larynx; such inspiratory wheeze may be accom panied by stridor, a loud phonated sound occurring during inspiration when the larynx is obstructed. Two notes of caution require m ention in th e context or wheeze. One is th at wheeze does not alw ays im ply disease of obstructive type. In pulm onary oedem a, for exam ple, where alveolar closure occurs during the breathing cycle, alveoli on the p oint of closure m ay be a source of wheeze, and this should not be taken to indicate the presence of asthm a as well. T he second point to bew are of is th a t severe airflow obstruction m ay be present in the com plete absence o f wheeze. In status asthm aticus, for exam ple, o bstruction may be so severe th a t there is ju st not enough airflow to generate wheeze. P leural friction rub T h e th ird category of adventitious sounds applies to conditions w here parietal or visceral p leural layers, or both, becom e inflam ed. T he two layers th en generate sounds as they rub together during breathing. The sounds are typically high-pitched, and o f a slightly “ ro u g h ” character; they m ay occasionally be squeaky, rem iniscent of brand-new leather shoes. T h e cadence of sound heard during inspiration is typically reversed during expiration. P leural friction rub is most com ­ m only observed in pleurisy, pneum onia an d pulm onary infarction (such as follow s pulm onary embolism). P R A C T IC A L USES O F A U SC U L A T IO N A uscultation is a valuable aid to diagnosis and follow -up. A u scultatory findings should, however, alw ays be used in conjunction with full physical exam ination, w ith the clinical history and, w here pos­ sible, w ith th e chest radiograph. A w illingness to auscul­ tate w ithout recognising these o th er factors is both inept and potentially dangerous. E xam ples have appeared above w here au scu ltato ry findings alone w ould have been am biguous, or even frankly m isleading. N evertheless, having accepted these constraints, the physiotherapist m ay be able to derive m uch useful inform ation via th e stethoscope, and so be able to tailor therapy for th e p a tie n t’s m axim um benefit. Q uestions frequently asked concern th e quality of ventilation to the various lung regions. Is there m ucus plugging in a certain are a ? O r an inhaled foreign body? A re th e lung bases atelectatic? Is pneum onia deve­ loping? O r p n eu m o th o rax ? W hich segm ents or lobes should be posturallly d rain ed ? T hese are all exam ples of questions to w hich auscultation m ay provide a p art of th e answ er. O ther questions relate to the general adequacy of ventilatory function. Is the p atien t retaining secretions despite attem pts to cough? C ould he be treated ad eq u ately if th e endotracheal tu b e were re ­ m oved? W hat effect are inhaled bro n ch o d ilato rs having? C O N C LU SIO N It should by now be ap p aren t th a t auscultation is by no m eans a sim ple procedure. A cquisition o f skill dem ands constant practice. U sed correctly and with circum spection, however, the technique can provide valuable inform ation to the physiotherapist engaged in the treatm en t an d prevention of chest disease. References Forgacs, P. (1978): L ungs sounds. B ailliere T indall. L qildon. L ittm an, D. (1961): A n A pproach to the ideal steth o ­ scope. J. A m e r . M ed . A ss., 13, 504 - 505. 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. )