BRONCHOSPIROMETRY - Postgraduate Medical Journal · Gebauer catheter has slightly larger airways, is moreradio-opaque, andthe tip, whichpasses into the left bronchus, is smaller.

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BRONCHOSPIROMETRYBy KENNETH W. DONALD, D.S.C., M.A., M.D., M.R.C.P.

Assistant Physician, Queen Elizabeth Hospital, Birmingham; Reader in Medicine,. University of Birmingham

In 1932 Jacobaeus, Frenckner and Bjorkmanfirst described the method of bronchospirographyusing a double-channelled bronchoscope. Satis-factory respiratory tracings showing the tidal air,ventilatory volumes, vital capacity and oxygenuptake of each lung were obtained. The respira-tory level of the subjects was raised (more air inthe chest than normally at the end of expiration)and the total vital capacity was reduced (Bjorkman,1934). These differences were due to the re-sistance of the instrument to respiration.

In 1939 Gebauer, and Zavod shortly afterwards,designed, quite independently, soft rubber bron-chial catheters which rendered the procedure lessunpleasant and traumatizing, and gave a maximumrespiratory excursion far nearer to the vitalcapacity as measured by external spirometry.These catheters have two channels, one openinginto the lower trachea and the other near the semi-rigid tip, which passes down the left bronchus.The distension of rubber balloons just above eachof these openings, segregates the two lungs. TheGebauer catheter has slightly larger airways, ismore radio-opaque, and the tip, which passes intothe left bronchus, is smaller. However manyworkers prefer the Zavod catheter. As Procter(1950) has stated, it seems to fit the anatomy better.After suitable local surface anaesthesia thecatheter is placed in the correct position underdirect fluoroscopic observation. The increased re-sistance to respiration still causes unpleasant sub-jective symptoms and the necessity for screeninglimits the use of the method.

In 1948 Norris and his 'associates evolved asingle-lumen catheter which passes uninterruptedfrom the left lung, through the mask, to the leftlung spirometer. The airway to the right lung isfrom inside the mask and round the left lungcatheter. The resistance of the catheter is aboutonly one-fifth of that encountered in the channelsof the double-lumen catheters, and the resistanceto the right even less. The catheter is also intro-duced under fluoroscopic control. There are, how-ever, a number of objections to this technique.The resistance to respiration is not the same forthe two lungs, and there is a considerable difference

in the dead space on each side. The vocal cordsmay contract round the catheter and cause furtherdiscomfort and resistance. Lastly, as workers inthis field well know, masks leak, no matter whatprecautions are taken.

Carlens (i949) has evolved a flexible, double-lumen, rubber catheter of about the same rigidityas an ordinary ureteric catheter. It has a smallrubber hook which automatically engages thecarina. This hook is tied down by a silk thread toallow passage through the larynx. After this, theintroducing stylet is removed and the catheteradopts its natural curve. The thread is pulled,releasing the hook and the catheter is turned, sothat the curve points the tip towards the left. It isthen passed down without fluoroscopy until thehook engages the carina, the tip of the catheterpassing into the left bronchus. Subsequently theprocedure is the same as with the other types ofcatheter. The lumen and resistance of eachchannel is approximately the same as that of theNorris single-lumen catheter. Although theauthor has not used this catheter yet, it appears, byall reports, to be a considerable advance.*

ProcedureThe procedure of bronchospirometry is best

studied by watching a team at work. It should becarried out in a special room. The two spiro-meters and respiratory circuits should be on atrolley, which can be fixed, and all the apparatusshould be carefully checked and in perfect workingorder before the patient comes in. Many workersemploy relatively low resistance non-return valvesin the spirometric circuit. This, however, meansthe adding of the resistance of the valves and theabsorbent canister to the already uncomfortable re-sistance of the catheter. The resistance to air flowshould be bench tested in all new catheters beforethey are used. Unpleasant respiratory resistancecan be minimized by the use of pum'ps to circulatethe gases through the absorbent canister, asoriginally described by Knipping. The catheters

* This catheter is now available in the sterling areafrom A. B. Stille-Werner, Stockholm 4, Sweden.

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172 POSTGRADUATE MEDICAL JOURNAL March 1952

are connected to a point in each circuit where thenegative and positive pressures each side of thepump are balanced, no valves are necessary, andthere is practically no added work to be done inbreathing, apart from that due to the catheter.The reason that pumps are not universally em-ployed is the considerable difficulty in obtainingand setting up efficient pumps that do not leak orcause unsuspected heating. Such events willfalsify the results and, as will be discussed later,this may cause tragically wrong decisions to bemade.

It is usual to carry out a preliminary broncho-scopy. In most cases where differential spiro-metric data is required, the information obtainedby bronchoscopy is essential. Ulceration of thetrachea and left main bronchus may be found andthis is a contraindication to bronchial catheteriza-tion. Difficulties due to deformity of the tracheo-bronchial tree may be anticipated and successfullyovercome. The finding of bronchial stenosis willgreatly help in the interpretation of results anddecisions concerning resection. Other contra-indications to bronchospirometry are recent spreadof tuberculosis, any pulmonary haemorrhage in theprevious two weeks, and recent acute laryngitis,tracheitis or bronchitis. Most patients findbronchospirometry 'relatively easy' to tolerateafter bronchoscopy. This is rather a Spartanphilosophy, but, as bronchoscopy is usuallyessential, it is fortunate that the more quantitativeprocedure is the less unpleasant. Routine externalspirometry for the determination of lung volumesand ventilatory capacity is best carried out before,as all these procedures are valuable training, apartfrom the important data they yield. The patient'schest should also be screened and an initial estima-tion of the relative functions of the two lungsshould be made and written down, taking intoconsideration the history and clinical findings iswell as the results of any special investigations. Inthis way invaluable experience is gained, the valueof the more orthodox methods of study enhanced,and errors of judgment long remembered.

If the patient is producing a great deal ofsputum, then a preliminary course of posturaldrainage should be carried out. It is most im-portant to attempt to clear the bronchial tree asnot only does the patient tolerate the cathetermore easily, but the local anaesthetic is moreeffective and there is less chance of blockage fromsecretions.Sodium amytal (gr. iii), or any appropriate

sedative can be given one hour before the examina-tion. A soluble intravenous barbitone preparationshould always be immediately available in case ofuntoward reactions. Half an hour before thecommencement, i to i gr. of morphine sulphate

should be given. Large doses of morphine must.be avoided. It is claimed that atropine sulphate(gr. if/oo) reduces the secretions, although manyothers, the author included, consider that thisdrug renders the secretion more viscid and trouble-some. After the patient has been lying quietly forhalf an hour, the back of the tongue, the fauces andpharynx are painted with 5 per cent. cocainehydrochloride, the tongue being held well forwardby the patient, who is given a swab for this pur-pose. The application of the anaesthetic with acamel hair brush keeps the quantity of cocainesolution required to a minimum and also preventsundue amounts being swallowed. The patientshould be warned about this and allowed to spit asfrequently as possible. There is no doubt thatspraying is a far more fortuitous procedure. Nextthe.pyriform fossa is anaesthetized by means ofsmall pledgets on specially curved laryngealforceps. Counter pressure should be appliedbelow and behind the angle of the jaw. Thepledget should be kept in position for at least aminute. This procedure is stated to anaesthetizethe superior laryngeal nerve. Others claim that itis unnecessary, but this is not the author's ex-perience.The larynx is then visualized by means of a

mirror and i cc. of 5 per cent. cocaine solution isinjected between the cords. This results in anexplosive cough followed by a deep inspirationwhich carries the remaining solution downwards,thus anaesthetizing the larynx and upper trachea.After a brief period, two further i cc. of solutionare injected into the trachea, while the patient leansover to the left side. Another i cc. is injectedwhile he leans over to his right side. Althoughanaesthesia of the right bronchus is not essential,it certainly appears to reduce irritation and cough-ing when the catheter is in place. The wholeanaesthetization is carried out while the patient issitting on the edge of the screening table, and itcannot be emphasized too strongly that unless thisprocess is carried out carefully, systematically andsatisfactorily, the whole procedure will fail. Notmore than 4 cc. of 5 per cent. cocaine hydro-chloride solution, or more than 8 cc. of i per cent.amethocaine solution, should be used. Whenanaesthesia is completed the patient is allowed tolie down for the next stage.There are several methods of introducing the

catheter and a metal guide is usually provided.However, in properly trained hands this is notnecessary. Nor is it necessary to use a mirror toenter the larynx, as the insertion of the catheter'blind,' with deep inspirations, soon results in itsentry into the trachea. Air can be heard, andfelt, passing through the catheter as soon as thisoccurs. Much depends at this stage upon the con-

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March 1952 DONALD: Bronchospirometry 173

fidence of the patient being maintained and abland and reassuring monologue from the operatorwill work wonders.

After passing the larynx the final placing of thecatheter is carried out under direct fluoroscopicobservation. As the catheter tip is semi-rigid andslightly curved, it is not difficult to pass it into theleft bronchus. The sudden turn of the catheterwill indicate its entry and, if passed further, itwill enter the lung field. The catheter should beleft just medial to the heart border and about 3 cm.from the carina. At this stage, or when theballoons are inflated, there may be troublesomecoughing. The practice of injecting furtheranaesthetic down the catheter may stop this, but itis an untidy technique and a very poor second bestto adequate and careful anaesthetization at thebeginning.When the patient has settled down the balloons

should be slowly and carefully inflated by means ofan air-filled syringe. As the balloons engage thewall of the respiratory passages they may not onlystimulate coughing but the patient will now besubject to the full resistance of the catheter andwill no longer be able to breathe around it. This isa very critical juncture and firm reassurance andinstruction to breathe deeply and calmly areessential. The author has, at times, invoked theawful lie that ' divers breathe through many feetof tubing and that it is only a matter of confidence.'The integrity of the balloons should have beentested previously in a glass tube of the shape andsize of an average trachea and bronchus. Manyof the balloons on these catheters are unsatisfactoryand it is wise to have a reserve of latex ballonsthat can be used for replacements. The pressureneeded for satisfactory sealing should also havebeen noted, so that it can be repeated by watchingthe manometers attached to the appropriatechannels. An unduly large trachea may causesome trouble with the upper balloon but examina-tion of the X-ray and bronchoscopy should giveadequate warning. Carlens uses a control balloonon the outer end of the channel so that the correctdegree of distension can be obtained without amanometer. Before commencing any observa-tions, it is important to listen carefully with astethoscope to the left upper lobe to check thatthere are normal breath sounds and good airentry. If the catheter has been inserted just alittle too far, the balloon may block the upper lobebronchus and thus cause low left lung readings.This auscultatory test is most unreliable and theonly adequate precaution is to see that the catheteris properly placed when screening. Herein liesanother important advantage of the carinal hook onCarlens catheter, as it prevents the catheterslipping before the balloons are distended.

As soon as the observer is satisfied that thecatheter is satisfactorily placed, then recordingsshould be started on the spirometers. There mustbe no delay, as time is precious. If the lungs arenot separated then the whole system is a commonchamber and one spirometer will empty into theother, as even the most minute differences of re-sistance are enough to cause such transference.This will result in the tracings either diverging orconverging. Another not uncommon event is dueto the upper balloon being too near the carina ordistending unequally and downwards. This mayresult in the right bronchus being blocked. Thepatient may or may not be distressed but, in anycase, the spirometer in the right-sided circuit willshow no movement. If the tracings are satisfactorythen they should be continued for about fiveminutes. This will allow a reasonably accuratemeasurement of the slope of the tracings. It is un-wise to assess oxygen uptake from a two minutetracing, particularly as the first minute is fre-quently unstable. Usually the increased resistancediscourages 'temperamental' changes' of respira-tory level and the slope of the tracing is very de-finite. Before terminating the test the vitalcapacity, reserve air and complemental air of eachlung should be determined. In some cases mildleg exercise against resistance is carried out, thechanges in ventilation and oxygen uptake beingnoted. Usually the patient will not tolerate a verygreat increase in activity and ventilation, butCarlens (I950, 1951) reports that, with his newcatheter, he is able to exercise patients on abicycle ergometer attached to the table, and thatthey will tolerate degrees of exercise involving upto I.5 1. O, consumption per minute. This is aconsiderable advance and it will be discussed later.

Finally it must be again emphasized that smooth,well-trained teamwork is essential. The pro-cedure is so near to the maximum of discomfortthat a patient will reasonably tolerate that theremust be no added unpleasant physical or psycho-logical stimuli such as unnecessary noises, cough-ing, inexpert or careless manipulation, or in-adequate anaesthesia. Wright ('Methods inMedical Research,' 1950) sums up the matter veryneatly by stating that the anaesthesia should becarried out at leisure and the intubation and re-cording in judicious haste. As soon as the requisiteinformation has been obtained the balloons aredeflated and the catheter removed. It is usual tomeasure the vital capacity at once with a mouth-piece, as the comparison of this figure with theadded vital capacities of the two lungs is a usefulcheck on the reliability of the recordings. Theusual precautions must be taken concerning thepatient drinking or eating before the anaesthesiahas passed off.

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174 POSTGRADUATE MEDICAL JOURNAL March 1952Another important consideration should be

mentioned. This is the question of causing re-activation or spread of tuberculous diseaseby bronchospirometry. Michelson and Wright(' Methods in Medical Research,' 1950) have re-viewed a large series of cases most carefully as tothis possibility and have found no evidence thatbronchospirometry precipitates such an event.Again there is the vexed problem of transmittingthe viable tubercle bacilli to another patient fromthe'apparatus. Although some authorities do notthink this is important in a group of tuberculouspatients, the recent development of streptomycinresistant strains may cause some danger. Theauthor, working entirely empirically, pumpsthrough the apparatus, for several hours, air whichhas been passed through a strong formalin solu-tion, and the apparatus is then washed out withair for a period. Rubber tubing is boiled andvalves are washed with ether. Surprisinglyenough there is no unpleasant taste or sensationafter this. As a general rule non-tuberculouspatients should not be tested on the same circuitsas tuberculous patients. This problem is usuallyevaded and it should be more fully discussed bythose whom it concerns.

Other Types of Data in BronchospirometryIt is of interest to consider other types of data

obtained by bronchospirometry. Attempts havebeen made to measure the ventilatory capacity ofeach lung by voluntary hyperventilation while thecatheter is still in place (Leiner et al., I940). Thisis a most unsatisfactory procedure as the stenoticbreathing renders such an effort most unpleasantand the figures obtained are far below the truefigures. Further, the catheter may be displacedor blocked during such an attempt. Others havemeasured the residual volume of each lung by theoxygen washout method or by the dilution of aninert gas. Such data is difficult to interpret.Fibrosis, collapse or infiltration of one lung maycause a small residual volume, and the totalcapacity of the lung may similarly be so alteredthat the relation of the residual volume to thisfigure will be of little value in assessing thepossibility of emphysema. In the same way, arelatively normal lung may be increased in size bymediastinal shift. It has been shown that evenhealthy lungs under such conditions will have anincreased total and residual capacity. Further, theresidual volume may be an abnormally high per-centage of the total capacity, without any impair-ment of the ventilatory capacity or any trueevidence of emphysema (Gaensler and Cugell,1951; Cournand et al., 1950). On the whole thevalue of such lung volume data does not appear towarrant the considerable trouble of collecting it.

Another method of investigation is to cause thelung which is to be removed or resected to breathepure nitrogen (Wright and Woodruff, 1942), or torebreathe into a small bag. There are a number ofways of interpreting the results obtained, but ifthere is but little disturbance or cyanosis (arterialsaturation may be measured), then this is con-sidered as good evidence of lack of function of thislung. Such a finding would certainly suggestconsiderable reduction of blood flow through thelung, but this can be demonstrated more preciselyby the more orthodox procedure of measuringoxygen uptake. Others block the bronchus of thelung or lobe to be resected (Jacobaeus and Bruce,I940) and, if this causes no disturbance, it is con-sidered good evidence that resection will causelittle alteration in the patient's respiratory function.Accurate arterial blood studies are rarely usedduring this procedure. All these various tests areonly carried out in near-basal conditions and in-ferences concerning ordinary activities andmoderate exercise after operation are unwarranted.Further the breathing of low percentages of oxygenor bronchial blockage almost certainly causesmarked vasoconstriction in even a healthy lung(Wright and Woodruff, 1942; v. Euler andLiljestrand, I946; Dirken and Heemstra, 1948;Rahn, 1950), and therefore conclusions concerningthe amount of blood flow while breathing air arenot justified.

Attempts have been made (Whitehead et al.,1942) to measure the ' reserve' of the ' goodlung,' which will remain after resection, by sub-mitting it to what is termed the 'stress' ofbreathing low percentages of oxygen. Theability of this lung to continue carrying out a largeproportion of the oxygen uptake under theseconditions is mainly a function of the lack ofcirculation through the other lung and is in noway related to its ability to ventilate adequatelyand accept and oxygenate the cardiac output duringreasonable exertion. Such procedures produceextremely complicated physiological situations ona background of disease and, although perhaps offundamental interest, they have no place or valueas a routine investigation.Meaning and. Value of Results Obtained

Having considered the details of technique andprocedure, let us now turn to the meaning andvalue of the data obtained by this method. Theventilation, vital capacity and oxygen uptake ofeach lung can be expressed as a percentage of thetotal under these conditions. The ratio of oxygenuptake of the two lungs is an accurate measure ofthe relative blood flow through them. As thepatient is breathing high percentages of oxygen,no matter how poor the distribution of inspired

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gas (i.e. the ventilation of all air spaces), a hightension of oxygen will soon result throughout eachlung. Thus, providing there is no pulmonarycirculation unrelated to air spaces, and this is un-likely, then all blood passing through the lung willbe fully oxygenated. Each unit volume of bloodpassing through the lung will take up an equalamount of oxygen. Therefore, although theabsolute values of blood flow are not known, as theoxygen content of the blood entering and leavingthe lungs is not measured, the comparative oxygenuptake 'of each lung is a precise quantitativemeasure of the relative blood flow. In normalsubjects the right lung usually has a ventilation,oxygen uptake and vital capacity which is about55 per cent. of the total. Occasionally this figureis even higher and in some cases the left lung mayshow about 55 per cent. of the total function asmeasured by these findings. Thus only figuresbelow 40 per cent. on either side can be con-sidered really significant.

If a non-return respiratory circuit is employedon each side and air is breathed, the expired gasesbeing collected in a Douglas bag, then the applica-tion of Fick's principle is no longer valid, as itcannot be assumed that all alveoli, through whichblood flows, are adequately ventilated and that allthe blood is fully oxygenated. Thus the oxygenuptake during air breathing, although moreaccurate than that obtained by a tracing, is not atrue measurement of the comparative blood flowthrough the lungs. Although two lungs may havean equal blood flow and oxygen uptake whilebreathing oxygen, if one of these lungs has somealveolar underventilation due to emphysema orbronchial obstruction, then this lung mar show aconsiderable fall of the percentage oxygen uptakewhen both lungs are breathing air. Further, underthese more natural gaseous conditions, there maybe vasoconstriction and decreased blood flow inthe underventilated lung. There is a real possibilitythat the administration of oxygen may artificiallyincrease the percentage of blood flow through anunderventilated lung by eliminating such vaso-constriction. In cases where there is a consider-ably greater percentage of oxygen uptake than ofventilation it may be wise to carry out air studiesas well. These considerations are mainlytheoretical although Carlens (1950) has recently re-ported some work showing significant changes inthe oxygen uptake of emphysematous lungs whenbreathing oxygen and when breathing air. Gaens-ler and Cugell (1951), using the box-bag spiro-metric technique (Donald and Christie, 1949),have also shown a remarkable decrease in theoxygen uptake of diseased lungs when air is sub-stituted for oxygen. It must be emphasized thatthe standard procedure at present involves breath-

ing oxygen and it is always assumed, unless statedotherwise, that this is the case.When bronchospirometry is performed it is

usually in order to determine, firstly, the functionof the diseased lung which is to be collapsed or re-sected and, secondly, if possible, the function of thelung that will remain after operation. The latteris, of course, the more important as the safety andthe comfort of the patient will depend upon this.Before considering how the findings in broncho-spirometry will help to answer these problems, itmust be emphasized that such studies only measurethe relative function of the two lungs and in no wayindicate the functional capacity and reserves ofeither lung. For example, if a person withcrippling bilateral emphysema were tested by thistechnique, the oxygen uptake and ventilation ofeach lung would be within normal limits and thevital capacity of the two lungs would be approxi-mately equal. Yet removal of either lung wouldprobably cause death from acute respiratory in-sufficiency. To carry this illustration further, ifsevere bulla formation began to occur in one lungin such a person, the percentage ventilation andoxygen uptake of the other lung would increasewell above the usual percentage and yet the lungwould be grossly diseased and incapable ofsustaining life.

Let us return to the consideration of the functionof the more markedly diseased lung, which is, ifpossible, to be collapsed or resected. In a numberof cases (severe tuberculosis, bronchiectasis, etc.)the ventilation, oxygen uptake and vital capacityare negligible. Only a small amount of air andblood enter the lung and it can be safely assumedthat it is virtually functionless, and that littlealteration in the patient's status will result fromits removal. Again, the fact that nearly ioo percent. of ventilation and oxygenation is carried outby the other lung does not prove that it is ahealthy lung. However, its true functionalcapacity can be assessed fairly well by studying thepatient's exercise tolerance and ventilatorycapacity. The assumption that the remaining lungwill function as well after resection as before isonly valid if the operation does not injure or de-form this lung.

Unfortunately many cases under considerationare not so clear cut as this. The patient may havesevere tuberculosis in one lung and the other lungmay be apparently normal or healed as judged byclinical and radiological data. Resection or ex-treme collapse of the diseased lung may be en-visaged. Yet if this lung shows 30 to 50 per cent.of total function the observer may find it difficultto decide whether this is due to a considerableamount of functioning lung tissue remaining,despite the disease, or whether this is due to the

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inability of the other lung to carry out morefunction. This type of argument is quite illogical,as if the diseased lung is taking up a significantportion of oxygen then there must be considerablefunctioning lung tissue present. Resection or ir-reversible collapse of such a lung should only becarried out if such a procedure is consideredabsolutely necessary to control the disease, and ifthe clinician is satisfied that the other lung hasalmost normal functional capacity. Again, in thistype of case, it is sometimes found that the morediseased lung (shall we say with fibrocaseousdisease and cavitation) is carrying out moreventilation and oxygen uptake than the lung whichnow appears healed or is even radiologically clearof disease. In such cases, there is almost invariablya history of pleural disease. Healed bronchialstenosis may give rise to a similar situation(Jacobaeus, 1938). It has been shown by manyinvestigators (Jacobaeus, I938; Pinner et al.,1942) that so-called parenchymal disease, whichmay be quite extensive and give marked radio-logical changes, frequently interferes but littlewith ventilation and oxygen uptake, whereas oldpleural disease (i.e. pneumothorax with fluid andlong delay in re-expansion), although showinglittle radiological abnormality, often causes grossimpairment of ventilation and oxygen uptake. Itis in this type of patient, where one lung has hadpleural involvement and appears healthy and theother lung requires collapse at a later date, thatbronchospirometry is so valuable. This findingthat old pleural involvement can cause severe andhitherto unsuspected impairment of lung functionshould be remembered when the advantages anddisadvantages of therapeutic pneumothorax arebeing considered, particularly as it has been shownby bronchospirometry that thoracoplasty, if nottoo extensive, and in the absence of diaphragmaticparalysis, leaves the lower portion of the lung witha considerable (up to 40 per cent.) amount offunction (Pinner et al., 1942). As already men-tioned, if there is but little ventilation and con-siderable oxygen uptake in a diseased lung, then adifferential study while breathing air. should bedone, as it is possible that the blood flow andfunction are far less under these more naturalconditions. A number of workers have suggestedthe possibility of a considerable ' shunt' of poorlyventilated and oxygenated blood through diseasedlungs, but it is only recently that attempts havebeen made to support this unlikely thesis byarterial blood studies before and after resection.With regard to the problem of prognosticating

the function of the remaining lung after resection,it must be realized that bronchospirometry canonly give very limited information in most cases.There has been a great deal of loose thinking about

this subject. What precisely is meant by thefunctional capacity of a lung after pneumonectomy?It is reasonable to employ the physiologicalcapacity of a normal lung, after removal of theother lung, as a standard. Cournand et al. (1950)have shown that one normal lung (defined as suchonly after detailed and demanding tests) will allowthe patient to live a normal life and even carry outmoderately severe exercise without any respiratoryor cardiac disability. Considering this in moredetail, such patients could undertake moderatelysevere exercise without ventilatory discomfort(dyspnoea), the flow of the total cardiac outputthrough the remaining lung did not cause an un-due rise of pulmonary artery pressure, or em-barrassment or hypertrophy of the right ventricle,and finally, despite the increased flow through onelung, the blood was normally oxygenated.

Unless one is dealing with a functionless lung,as previously discussed, then the assessment of therisk involved and the prognostication of the maxi-mum function of the remaining lung is mostdifficult. In the case of the diseased lung, whichis to be collapsed or resected, showing, shall wesay, 40 per cent. of function at comparative rest,it is often suggested that, on more marked exertion,the affected lung will not be able to continue tocarry out such a high proportion of ventilation andoxygen uptake. Such an attitude, and it is quite areasonable one, may lead to resection in ' border-line' cases. It is very human to want the organwhich is to be removed to be relatively functionlessand this is therefore a tempting hypothesis. How-ever, Carlens (1950, 1951) using his new type ofcatheter, has been able to exercise patients up toan oxygen consumption of I,500 cc. per minuteand obtain satisfactory differential studies. Theseexperiments have shown a remarkable constancy ofthe ratio of ventilation and oxygen uptake in alldegrees of activity. This is a very importantobservation and demands more realistic thinking.It means that, despite the disease present, collapseor resection often demand a high price in terms offunction, and care must be taken that this pricecan be paid and that the remaining lung will haveadequate function, as defined above, to make lifetolerable. It is important to note that Carlens'observations were made while using oxygen en-riched mixtures and these exercise studies shouldbe repeated while breathing air.

In the case of patients with relatively recent butsevere unilateral disease and no previous historyof asthma, bronchitis or any other respiratorydisability, it is reasonable to assume that theremaining lung tissue is healthy and that resectionor collapse of a whole lung would not cause anygreat disability. However, if the patient is older, ifthe history and clinical findings suggest emphy-

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sema or fibrosis, or if the other lung has beendiseased pr collapsed, then great care must betaken. The present exercise tolerance should bedetermined. Exercise tests may not be feasible ifthe patient has been strictly at rest in bed for a con-siderable period. The ventilatory capacity (maxi-mum breathing capacity) can be measured andthe capacity of the lung that is to remain can beapproximately calculated. It should be re-membered that after resection the ventilatorycapacity will be considerably more than thedemonstrated percentage of total ventilation, as thesingle lung compensates by more rapid but smallerrespirations. A normal lung under these con-ditions can sometimes give a maximum breathingcapacity as great as that obtained with two healthylungs (Cournand et al., 1950). There is a greatdeal more work to be done on this problem.Warring (1949) prognosticates the ventilatorycapacity of the lung before resection by determin-ing the maximum breathing capacity and thenwatching the ventilatory movements during screen-ing. Another most important observation is theminute ventilation of the patient during moderateexercise (walking, etc.). This can be measured bycollecting the expired air in a Douglas bag over areasonable period. It has been shown by Warring(I949) that these ventilatory demands alter butlittle, no matter what surgical procedures arecarried out. The relation of these figures, whichvary enormously, to the prognosticated ventilatorycapacity will give some idea of the degree ofexercise that will be tolerated without dyspnoeaafter operation.As the majority of cases in whom collapse and

resection are carried out are relatively young peoplewith tuberculosis, or quite young people withlocalized bronchiectasis, and these people do nothave marked emphysema or generalized lungdisease, the main problem is a ventilatory one andthe possibility of right heart embarrassment andinability to oxygenate the arterial blood are remote.Careful ventilatory studies and consideration of thepossibility of ventilatory insufficiency and dyspnoeaare therefore most important and rewarding. Inpatients with considerable lung damage, such aspulmonary emphysema or fibrosis, pleural fibrosis,or massive healing, resection or collapse may bemost hazardous. Ventilatory problems can bestudied as already outlined. Circulatory con-siderations are more difficult and can only be in-vestigated by highly specialized procedures suchas by cardiac catheterization with pressure record-ing during rest and exercise. Carlens' observationthat differential blood flow remains constant shouldbe a great help in such studies. Electrocardio-graphic studies and screening will give furtherevidence of the state of the right heart. Arterial

blood studies with exercise are also of value.These brief observations emphasize that

although bronchospirometry is a valuable pro-cedure in assessing differential lung functions itcannot by itself enable the investigator to foretellfunction after operation. More general studiesand considerations are necessary for such prog-nostication, and there is a great deal of work stillto be done in this field.

Future PossibilitiesIt is of interest to consider what procedures

would make it possible, in difficult cases, to assessthe functional capacity of a single lung moreprecisely before operation, so that it could bedefinitely stated whether or'not this single lungwill be able to support reasonable activity afterresection or collapse of the other.

Let us first consider the ventilatory capacity.The techniques and difficulties of this assessmenthave already been discussed. Although the con-tribution of each lung to the total ventilatorycapacity can be fairly well determined by broncho-spirometry or screening, it is difficult to determineprecisely what the performance of this lung will bewhen functioning alone. A feasible method wouldbe to pass a thin catheter, with a balloon attached,down the bronchus of the lung that is to be re-sected. This bronchus could then be occludedwith a minimum of interference with the air wayto the other lung. Ventilatory tests (maximumbreathing capacity) could be carried out in thisstate and the figures obtained related to thepatient's ventilation during moderate exercise.Such data would enable the observer to give analmost precise estimation of the degree of activitythat will be possible without dyspnoea or ventila-tory embarrassment. There is a theoreticalobjection to this simple procedure. It is possiblethat the increase of blood flow through the lungafter operation may alter its ventilatory capacity.The complete and final test would be the oc-clusion, not only of the bronchus as described, butalso of the appropriate branch of the pulmonaryartery by a saline or diodrast filled balloon on acardiac catheter. If, under these conditions thesupine patient could exercise on an ergometer, upto a reasonably high oxygen uptake, withoutventilatory distress, or a significant rise of pul-monary artery pressure, or arterial desaturation,then it would be possible to state that the lung wasrelatively normal and that function would beadequate after operation. This procedure wouldensure virtual physiological amputation of the lungand this is probably the only way of assessing thepatient's function after its resection. There isalways, of course, the proviso that the operationwill not injure or deform the remaining lung.

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The temporary occlusion of the pulmonaryartery has been shown by Hansan (I95i), aftermany animal experiments, to be safe in the humansubject, at least, at rest. The simultaneousblockage of bronchus and artery has not yet beenreported, but it is probably only a matter of timebefore it is done. The original concepts of manychest and heart operations, which are now aroutine procedure, were far more dramatic andapparently dangerous than that of simultaneousbronchial and pulmonary artery blockage. It isan odd comment on human nature that a con-siderable number of patients have died after ill-judged resections, with little more than a transientregret by thome involved that the best judges canmake mistakes, but' the suggestion that simul-taneous bronchial and pulmonary artery blockagebe carried out, will cause many to rise up and pro-test against unjustifiable experimentation. Yet a'doubtful resection' is, of all things, an un-justifiable experiment, no matter by what standardsit is judged. Further, unsuccessful operations areinclined to be forgotten or lead to all border-linecases being rejected, when operation may befeasible and life-saving (i.e. bronchial carcinomawith generalized pulmonary emphysema).

Final CommentBronchospirometry is not a difficult investiga-

tion and yet it is but little used in this country.

Although it was described nearly 20 years ago and,year after year, both chest surgeons and physiciansstate how invaluable such- data would be, themethod does not come into general use. What arethe reasons for this odd state of affairs? Manyphysicians and surgeons, who practice the moredifficult procedure of bronchoscopy, considerthat bronchospirometry requires a considerableknowledge of respiratory physiology and its ex-perimental methods. This is quite untrue andany competent medical man could be adequatelytrained in a few months. Others hope, usually invain, that such a service will be provided byanother department. However, the few peoplewho have trained with highly-skilled groups,usually wish to devote their time, outside theirdirect clinical activities, to more fundamental workand do not wish to become involved in a routineinvestigation, which could be adequately per-formed by an efficient registrar.

It is true that the results can be misinterpretedand that faulty technique may cause incorrect and,perhaps, dangerous decisions to be made, but suchcriticisms apply to many other special tests whichare in daily use.

Finally, if the physicians and surgeons, who wishto avail themselves of this technique, really in-sisted that those who are training in thoracicmedicine and surgery should devote a few monthsto mastering it, then the method would be widelyused in a year or two.

BIBLIOGRAPHY

BJORKMAN, S. (1934), Acta med. Scand., Suppl. 56.BJORKMAN, S., and CARLENS, E. (x95o), Acta Oto-laryng. (in

press).CARLENS, E. (949), .7. Thorac. Surg., x8, 742.CARLENS, E. (x1sI), communication, Thoracic Society, Feb.COURNAND A., RILEY, R. L. HI1IMELSTEIN, A., and

AUSTRIAN, R. (95o), J. Thorac. Surg., i9, 8o.DIRKEN, M. N. J., and HEEMSTRA, H. (1948), QtArt. J.

Exper. Physiol., 34, 193.DONALD, K. W., and CHRISTIE, R. V. (I949), Clin. Soc., 8, 21.GAENSLER, E. A., and CUGELL, D. W. (i95x),-Proc. Amer.

Soc. Clin. Invest., June.GEBAUER, P. W. (1939), J. Thorac. Surg., 8, 674.HANSAN, L. (i95s), communication, Thoracic Society, Feb.JACOBAEUS, H. C. (1938), J. Thorac. Surg., 7, 235.JACOBAEUS, H. C., and BRUCE, T. (1940), Acta med. Scand.,

os5, I93.

JACOBAEUS, H. C., FRENCKNER, P., and BJORKMAN, S.(1932), Ibid., 79, I74.

LEINER, G., PINNER, M., and ZAVOD, W. A. (1940), J. Thorac.Surg., 10, 32.

'Methods in Medical Research,' Vol. 2 (1950), Chicago, Year BookPublishers.

NORRIS, C. M., LONG J., OPPENHEIMER, M. J., andWESTER, M. R. (x948), J. Thorac. Surg., 17, 357.

PINNER, M., LEINER, G., and ZAVOD, W. A. (1942), Ibid.,II, 241.

RAHN, H. (i950), personal communication.v. EULER, U. S., and LILJESTRAND, G. (1946), Acta physiol.Scand., 12, 301.WARRING, F. C., Jun. (1949), Amer. Rev. Tuber., 6o, 149.WHITEHEAD, W. K., O'BRIEN, E. J., and TUTTLE, W. M.

(1942), J. Thorac. Surg., xI, 266.WRIGHT, G. W., and WOODRUFF, W. (1942), J. Thorac.

Surg., zI, 241.ZAVOD, W. A. (1940), . Thorac. Surg., 10, 27.

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BRONCHOSPIROMETRY - Postgraduate Medical Journal · Gebauer catheter has slightly larger airways, is moreradio-opaque, andthe tip, whichpasses into the left bronchus, is smaller.

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