JournalofClinicalPathology197932882892Themorphologyofemphysemachr - PDF document

JournalofClinicalPathology,1979,32,882-892Themorphologyofemphysema,chronicbronchitis,andbronchiectasis:Definition,nomenclature,andclassificationB.E.HEARD,V.KHATCHATOUROV,H.OTTO,N.V.PUTOV,ANDL.SOBINFromtheBromptonHospital,London,theWorldHealthOrganization,Geneva,theInstituteofPathology,Dortmund,WestGermany,andtheInstituteofPulmonology,Leningrad,USSRThepurposeofthisdocumentistoproposedefinitionsandamorphologicalclassificationofemphysema,chronicbronchitis,andbronchiectasis.Itisaimedatprovidinguniform,internationallyacceptablestandardstofacilitatethecomparabilityofdatainthefieldofchronicnon-specificrespiratorydiseases.Receivedforpublication20March19794stx.0~~~~~~..4'Thedefinitionsanddescriptionsareintentionallybriefandaredesignedtoassistinthecleardelineationofparticulartypesoflesions.Theyarenotintendedtobefullaccountsofthediseases.Thedefinitionsarebasedprimarilyonmorpho-logicalcharacteristics.Pathogeneticandaetiologicalaspectsaretakenintoconsiderationwherenecessarybutarenotsufficientlyestablishedtoserveasthebasisofastandardizedclassificationatthepresenttime..'.N..4(aFig.1Normaladultlung.Histologicalappearanceafterpressure-fixationwithformolsaline.Thelargerair-spacesarealveolarductswithintactalveoliopeningintothem.ComparewithFig.2(Haematoxylinandeosinx75).882W."h1"-I,!7-.I.0,41,.X-14'..41- Themorphologyofemphysema,chronicbronchitis,andbronchiectasisMorphologicalclassificationofpulmonaryemphysema1Vesicularemphysema(a)Panlobular(b)Centrilobular(c)Paraseptal(d)Irregular(e)Unclassified2InterstitialemphysemaDefinitionsandexplanatorynotesPulmonaryemphysemawillbeconsideredinthepresentaccountundertheheadingsvesicularandinterstitialemphysema.1VESICULAREMPHYSEMA:anabnormalincreaseinthesizeofairspacesbeyondtheterminalbronchioleswithdestructionofairspacewalls.Somedefinitionsincludeinthetermemphysemacaseswi

thirreversibledilatationofairspaces,referringtoitasdistensiveemphysema(Heard,1958;CIBAGuestSymposium,1959);othersconsideritseparatefromemphysemaanddescribeitasover-inflation(AmericanThoracicSociety,1962).Forpracticalpurposeshistologically,emphysemaismoreeasilydefinedasdestructionofairspacewalls,sincethedegreeofdilatationofairspacescanvaryverymuchaccordingtothemethodoffixation(Figs1and2).Forcarryingoutsubtypingandgradingofemphysema,themacroscopicexaminationoflargeslicesoflungisrecommendedratherthanhisto-logicalexamination.Becauseofthismacroscopicapproachthelobuleratherthantheacinushasbeenchosenasthebasisofthefollowingdefinitionsandhencethefirst-choiceterms(Pig.3).Emphysemacanbegradedasmild,moderate,andsevere.(a)Panlobularemphysema'(panacinaremphysema2):aformofemphysemathatinvolvesallairspacesbeyondtheterminalbronchiolesinarelativelyuniformmannerthroughoutaffectedlobules(Figs2and5).(b)Centrilobularemphysema3(centriacinaremphy-'TermproposedbyWyatt(1959).2TermproposedbyCIBAGuestSymposium(1959).3TermproposedbyLeopoldandGough(1957).f.tW-Joll,-9,i,k1b.,00~_.1-1,914e*%.1t-mi-/'1-/11/f..l-.Fig.2Panlobularemphysema.Histologicalappearanceofadultlungshowinglossofmanyalveolarwalls.ComparewithFig.1(HandEx75).883 NormalAcinusCentrilobularEmphysemaPanlobularEmphysemaFig.3Diagramofalobuleofthelungcomposedofsixacini,illustratinganormalacinus,centrilobularemphysema,andpanlobularemphysema.Fig.4Normaladultlung.AppearanceofthecutsurfaceforcomparisonwithFigs5and6(Pressure-fixation,bariumsulphateimpregnationsx13.7). Themorphologyofemphysema,chronicbronchitis,andbronchiectasisFig.5Panlobularemphysemashowingdestructionofmostofthealveolarwalls.ComparewithFig.4(Pressure-fixation,bariumsulphateimpregnationx15).semal):aformofemphysemathatinvolvesairspacesinthecentreoflobules(Fig.6).Thetermcentrilobularemphysemashouldbe

usedwhetherornottherearedeposistsofdustwithinthelesion.(c)Paraseptalemphysema2:aformthatinvolvesairspacesattheperipheryoflobules(Fig.7).(d)Irregularemphysema3:aformofemphysemathataffectsdifferentpartsofdifferentlobules.(e)Unclassifiedemphysema:aformofemphysemathatdoesnotfitanyoftheabovecategories.Forexample,casesinwhichthereisdifficultyindecidingbetweenseverecentrilobularandpanlobularemphy-semawithemptylobules,orbetweencentrilobularandirregularemphysema,shouidbecategorisedunder(e).NBThiscategoryshouldnotbeused,ifpossible,formixturesoftypes(a)-(d).Insuchcaseswithmixedmorphology,thespecifictypesshouldbe1TermproposedbyReid(1967).2TermproposedbyHeard(1958;1959;1960;1969).3TermproposedbyCIBAGuestSymposium(1959).recordedseparatelyandcategorisedcollectivelyaccordingtothepredominanttype.Abullaisafocusofseverevesicularemphysemawithaballoon-likeappearancewhichhasbeendefinedasbeingmorethan1cminthedistendedstate(CIBAGuestSymposium,1959).Casesofemphysemawithbullaeshouldbeclassifiedundertypes(a)-(e)andnottermed'bullousemphysema'.Aformofverylocalisedemphysemawithbullaeisrecognised;ruptureandspontaneouspneumothoraxoccur.Thisformcanbecategorisedunder(d),irregularemphysema.Pulmonaryfibrosismaybeassociatedwithdilata-tionofairspacesbeyondtheterminalbronchioles,producingaresemblancetoahoneycomb.Suchcasesareclassifiedasformsofpulmonaryfibrosisratherthanemphysemaandhavebeendescribedasemphy-sematouslungsclerosisorhoneycomblung(Otto,1970;1971).Thetermsenileemphysema(senilelung)isnotintheaboveclassificationasitisnotamorphologicalterm;itisusedbysomeauthorstodescribetheconditionofenlargedairspacesinelderlypeople,especiallyintheupperpartsofthelungs.Thischangeiscommonandcanberegardedconvenientlyaswithinthenormalrangeofairspacesizeratherthan885 B.E.Heard,V.Khatchatourov,H.Otto,N.V.Putov,andL.Sobin~~~~~~~~~~~~~~~........

..----Fig.6Centrilobularemphysemashowingbronchiolesleadingintotheemphysematouslesionsandnormalalveolisurvivingattheperipheryofthelobule.(Pressure-fixation,bariumsulphateimpregnationx11).aformofemphysema.Emphysemainelderlypeopleshouldbecategorisedaccordingtotypes(a)-(e)above.2INTERSTITIALEMPHYSEMA:aformofemphysemawithinflationoftheinterstitialtissueofthelungbyairorgas.Interstitialemphysemamayspreadtothemediastinumandsubcutaneoustissue.Ablebisamarkedballoon-likelocalcollectionofairintheinterstitialtissues.Theterminterstitialemphysemaispreferredtointerlobularemphysemabecausethelatterfailstoincludeemphysemaoftheinterstitialtissueofthealveolarwalls.MethodsThebestwaytoinvestigatealungforemphysemaistoinfuseorinflateitwithfixative.Subsequentlythelungisimmersedinfixativeforafewdaysbeforebeingcut.Forquantitativestudies,pressure-fixationisnecessarytoensureadequateinflationofallareasinauniformmanner(seeAppendix).Ifthefindingsarerequiredquickly,onelungmaybeslicedanhourafterinfusion,althoughlongerfixationgivesbetterresults.Afterfixationthelungcanbeexaminedaswetwhole-lungslicesinwaterinatray(facilitatedbyimpregnationwithbariumsulphate)and/orafterthepreparationofpaper-mountedwhole-lungsections.Bothmethodsareeasytocarryoutandnotverytime-consuming(seeAppendix).Severalmethodsareavailableformeasuringtheamountofemphysemainlungslices,andallproducereliableresults.Theyincludeaquicksix-zonemethod,point-counting,comparisonwithphoto-graphsofstandards,andagridof10radiatingsegments(seeAppendix).CHRONICBRONCHITIS:usuallydefinedinclinicaltermsasachronicinflammatoryconditionofthebronchiproducinganincreaseinmucussecretionbytheglandsofthetracheobronchialtreeresultingintheexpectorationofmucusatsometimeofthedayforatleastthreemonthsoftwoconsecutiveyears.886 Themorphologyofemphysema,chronicbronchitis,andbronchiectasisFig.7Para

septalemphysemashowingdestructionofair-spacesattheperipheryoflobules.Centrilobularemphysemaispresentalso.(Pressure-fixation,bariumsulphateimpregnation).Pathologicallythebronchialwallmaybethick-ened,andthefollowingfeaturesmaybeobservedhistologically:enlargementofthemucousglands,dilatationofmucousglandducts,anincreaseinthenumberofmucouscellsintheaciniofmucousglands,gobletcellhyperplasiaandsquamousmetaplasiaofthesurfaceepithelium,avariabledegreeofchronicinflammatorycellinfiltration.Chronicbronchiolitisisoftenassociatedwithit,andtheremaybenarrowingorobliterationofthelumen(Reid,1967;Heard,1969).Bronchoscopicstudiessuggestthattheremaybeseveralkindsofchronicbronchitis,butsubdivisionoftheserequiresfurtherpathologicalresearch.BRONCHIECTASISBronchiectasis:irreversibledilatationofbronchi,usuallyassociatedwithinflammation.Thedilatationofabronchuscanbeappreciatedbycomparingitsdiameterwiththatoftheaccompany-ingpulmonaryartery,whichisnormallysimilar887 B.E.Heard,V.Khatchatourov,H.Otto,N.V.Putov,andL.SobinFig.8Diagramofapparatususedforpressure-fixationofthelung.Thecentrifugalpumpraisesformalintotheuppercontainerandiscontrolledbyafloatandswitches(seeAppendix).(OttoandRein,1971).Twobasicpatternsofbronchialdilatationareencounteredmacroscopicallyandarenamed,accord-ingtotheirshape,cylindricalandsaccular.Fig.9Diagramshowingsix-zonemethodformeasuringemphysema(seeAppendix).Cylindricalbronchiectasis:usuallyinvolvesbasalsegments(Fig.10),andthelumenoftencontainspurulentmucus(Spencer,1977).Fusiformbron-chiectasisisincludedinthiscategory.Microscopicallythebronchialmucosamaybeheavilyinfiltratedbylymphocytesandplasmacells,andlymphoidfolliclesmaybepresent,especiallyinchildren.Bronchialglandsandcartilagemaybedamagedordestroyed.Saccularbronchiectasis(Spencer,1977):inter-mediatebronchiaredilatedtoformroundedblindsacs(thatus

uallydonotcommunicatewiththeparenchyma)andmaycontainpurulentmucus(Fig.11).Histologically,thereischronicinflammationandfibrosis,andbronchialglandsandcartilagemaybedestroyed.Otherterms,suchascongenitalandatelectaticbronchiectasis,refertomechanismsratherthanmorphology.Itisworthnotingthatbronchiectasismaybeidiopathicorassociatedwithchronicparenchymalinflammation,bronchialobstructionbyforeignbodiesortumoursorpost-tuberculousscarring,chroniccollapseofthelung,congenitalanomalies,andcysticfibrosis(mucoviscidosis).Thereisaspecialformofcylindricalbronchiectasiswhichaffectsproximalbronchiasaconsequenceofthebronchialinvolvementinallergicbroncho-pulmonaryaspergillosis.888 ThemorphologyoJemphysema,chronicbronchitis,andbronchiectasisFig.10Cylindricalbronchiectasis(Pressure-fixation,bariumsulphateimpregnationx23).AppendixMETHODSFORPREPARINGWETLUNGSLICESFOREMPHYSEMA(Heard,1958;1959;1960;1969)(a)MethodforfixinglungsunderastandardpressureMucusissuckedfromthebronchiandacannulaistiedtightlyintothemainbronchusandattachedtothetubefromtheuppercontainerof10%formolsaline,asseeninFigure8.Thelungisplacedinthelowercontainerandallowedtodistendslowlyunderapressureof25-30cmofaqueousformalinwhichisthenmaintainedforatleast24hoursbutpreferably72hours.Whenthelevelintheuppercontainerfallsbelowacertainmark,afloatswitchcausesthepumptoraisethelevelagain.Thelungiscoveredwithathinlayerofmuslintokeepitmoist.Thismethoddistendsairspacestoadegreecomparabletofullinspirationinlifeandpreventsunevendistension,whichisinevitablewithspecimensmerelyfilledwithformalinonceandimmersedinformalin.889 B.E.Heard,V.Khatchatourov,H.Otto,N.V.Putov,andL.SobinFig.11Saccularbronchiectasis.(Pressure-fixation,bariumsulphateimpregnation).(b)MethodforcuttingwetlungslicesThefixedlungmaybeplaced,lateralsurfacedown-wards,onaboard25x30cmfitteddownthetwolongsidesw

ithknife-supportsraised8mmabovetheboard.Along,verysharpknifeisrestedontheraisededges,andseveralanteroposteriorslicesarecutfromthelungforexamination.(c)MethodforbariumsulphateimpregnationofwetlungslicesforemphysemaAselectedsliceoflungislightlysqueezedfreeofexcesswaterandplacedflatinatray25x30cmcontaining1litreofsaturatedaqueousbariumnitrateatroomtemperaturefor1minute.Itispressedintermittentlywiththefingertips(protectiveglovesshouldbeworn)toencouragethesolutiontoenterthedepthsoftheslice,thengentlysqueezedtoreturnmostofthesolutiontothetray,andtrans-ferredtoasimilartrayof1litresaturatedsodiumsulphate,alsoatroomtemperature.Awhitecloudofprecipitatedbariumsulphateappears,andafter1minutethesliceiswashedinwaterandexaminedina890 Themorphologyofemphysema,chronicbronchitis,andbronchiectasistrayofcleanwaterbynakedeyeandhand-lensordissectingmicroscope.Themethodrendersthenormallytranslucentalveolarwallsopaqueandmoreeasilyvisibleinwater,andemphysematouschangesthusbecomemoreeasilyseen.Subsequenthistologyisnotimpaired.Photographyofemphysemaisimproved,andthewhiteningispermanentandsuitableformuseumpreparations.METHODFORPREPARINGWHOLELUNGSECTIONS(GoughandWentworth,1949,1960)Thickslicesofalungfixedinformalininthedistendedstateareembeddedingelatin,andsectionscut400,uthickonalargemicrotomearemountedonpaper.Thesectionsaresuitableforfilingwithotherpapersandforsendingthroughthemail.Caremustbetakenduringprocessingtopreventdigestionofthegelatinbyenzymesfromthetissuesofthelungorfromcontaminatingorganisms(MedicalResearchCouncilCommittee,1975).METHODSFORMEASURINGEMPHYSEMA(a)Arapidsix-zonemethodformeasuringemphysema(HeardandIzukawa,1964)ThesixzonesareillustratedinFigure9.Apreparedwetslice,impregnatedwithbariumsulphate,isexaminedwithahandlensordissectingmicroscopetoassessthechangeindetail,andthenbythenakedeyetheareaisdivid

edvisuallyintosixzonesofequalarea(usingmetalprobes).Eachzoneisawardedupto3unitsaccordingtotheproportionoftheareaemphysematous.Halfunitsarealsocounted.Theresultisstatedasanumberofunitsoutof18totalunits.Thepercentageoftheslicethatisemphysema-tousisobtainedbymultiplyingby5.5.(b)Apoint-countingmethodformeasuringemphysema(Dunnill,1962)Wetlungslicesorpaper-mountedwhole-lungsec-tionsmaybeexaminedunderatransparentplasticgridcarryinganarrayofpoints(orsmallholes)arrangedinahexagonalpattern(eg,4mmapart).Ateachpointarecordiscountedofnormallung,emphysematouslung,ornon-alveolatedtissuesuchasbloodvesselorbronchus.Emphysemamaybeexpressedasapercentageoftheareaofaslice,orseveralslices,orofthevolumeofalung.(c)Amethodformeasuringemphysemausingcomparisonwithphotographsofstandards(Thurlbecketal.,1970)Paper-mountedwhole-lungsectionsarepreparedandcomparedwithastandardsetofphotographsofselectedwhole-lungsections.Themethodisquick,andtheresultsaresimilarfromdifferentobservers.Thescoresrepresentarbitrarilyderivedgradesofseverity.(d)Amethodformeasuringemphysemausingagridof10radialsegments(Ryderetal.,1969;Goughetal.,1967)Aplasticgridmarkedbyacircledividedbyfivestraightlinesinto10equalsegmentsisplacedoverawetsliceorpaper-mountedwhole-lungsectionwiththecentrepointoverthemid-pointoftheinterlobarfissureandwithanyoneofitslineslyingalongthefissure.Emphysemaineachsegmentisassessedas0absent,1mild,2moderate,3severe,givingamaximumtotalof30points.METHODSFORQUANTITATINGHISTOLOGICALCHANGESOFCHRONICBRONCHITISThemainpathologicalevidenceforthemucoushypersecretionobservedclinicallyinchronicbronchi-tisisenlargementofthebronchialmucousglands.Therearethreemethodsformeasuringthis.(a)Gland/wallthicknessratiomethod(Reid,1960;1967)Transversesectionsofmainorlobarbronchiareexaminedbymeansofagraticulesetintheeyepieceofamicroscope.Atasitewherecar

tilageisroughlyparalleltothesurfaceepithelium,thedistancefromtheepitheliumtothecartilage(W)ismeasuredand,atthesamepoint,thedepthofthemucousglandlayer(G).Themeanofseveralmeasurementsiscomparedwithanormalrange0-14-0-26forG(b)Cut-outandweighmethod(RestrepoandHeard,1963aandb)Transversesectionsofselectedbronchiareprojectedatamagnificationofx10onplainwhitecard,ameasuredareaofwhichisfirstweighed.Theoutlinesofthebronchialglandsarethendrawnonthecardandcutoutandweighed.Theactualareasoftheglandsinsectionscanbeobtainedinthiswayandevaluatedbycomparisonwithcontrols.Thismethodcanalsobeusedtomeasurecartilageandwholewalls(RestrepoandHeard,1964).(c)Point-countingmethodSectionsofbronchiareprojectedonascreenmarkedwithagridofpoints.Thenumberofpointscor-respondingtobronchialglands(ormuscle,etc)iscountedandisexpressedastheareasofglands(ormuscle,etc)inabsolutenumbersinselectedbronchi(MacleodandHeard,1969;HossainandHeard,1970)orasaratiotopointscorrespondingtocartilage,expressedasapercentage(Dunnilletal.,1969).891 892B.E.Heard,V.Khatchatourov,H.Otto,N.V.Putov,andL.SobinThisworkwasinitiatedandsupportedbytheWorldHealthOrganization.Wearegratefultothosepathologistswhoprovidedhelpfulcriticismsandsuggestions.Figures1,2,5,8,and9arefromPathologyofChronicBronchitisandEmphysemabyHeard(1969)andreproducedbypermissionofChurchillLivingstone,Edinburgh.Figures4,5,6,7,10,and11werephotographedforDrB.HeardbyMrW.BrackenburyatthePostgraduateMedicalSchool,London,andFigs1and2bytheMedicalIllustrationServiceoftheUniversityofEdinburgh.ThediagraminFig.3waspreparedbytheDepart-mentofMedicalIllustration,RoyalMarsdenHos-pital,London.Figure8isreproducedbypermissionoftheEditoroftheAmericanReviewofRespiratoryDisease.Figures10and11arereproducedbyper-missionoftheEditoroftheBritishMedicalJournal,(Fig.10-2,1468-1476,1959;Fig.11-2,352-355,1965).Referenc

esAmericanThoracicSociety(1962).Chronicbronchitis,asthmaandpulmonaryemphysema.AstatementbytheCommitteeonDiagnosticStandardsforNon-tuberculousRespiratoryDiseases.AmericanReviewofRespiratoryDiseases,85,762-768.CIBAGuestSymposium(1959).Terminology,definitions,andclassificationofchronicpulmonaryemphysemaandrelatedconditions.Thorax,14,286-299.Dunnill,M.S.(1962).Quantitativemethodsinthestudyofpulmonarypathology.Thorax,17,320-328.Dunnill,M.S.,Massarella,G.R.,andAnderson,J.A.(1969).Acomparisonofthequantitativeanatomyofthebronchiinnormalsubjects,instatusasthmaticus,inchronicbronchitis,andinemphysema.Thorax,24,176-179.Gough,J.,Ryder,R.C.,Otto,H.,andHeller,G.(1967).VergleichendemorphologischeUntersuchungenzurHaufigkeitdesLungenemphysems.FrankfurterZeit-schriftfiirPathologie,77,317-327.Gough,J.,andWentworth,J.E.(1949).Theuseofthinsectionsofentireorgansinmorbidanatomicalstudies.JournaloftheRoyalMicroscopicalSociety,69,231-235.Gough,J.,andWentworth,J.E.(1960).Thinsectionsofentireorgansmountedonpaper.InRecentAdvancesinPathology:7thedition,editedbyC.V.Harrison,pp.80-86.Churchill,London.Heard,B.E.(1958).Apathologicalstudyofemphysemaofthelungswithchronicbronchitis.Thorax,13,136-149.Heard,B.E.(1959).Furtherobservationsonthepath-ologyofpulmonaryemphysemainchronicbronchitics.Thorax,14,58-70.Heard,B.E.(1960).Pathologyofpulmonaryemphysema.Methodsofstudy.AmericanReviewofRespiratoryDiseases,82,792-799.Heard,B.E.(1969).PathologyofChronicBronchitisandEmphysema,pp.65-66.Churchill,London.Heard,B.E.,andIzukawa,T.(1964).PulmonaryemphysemainfiftyconsecutivemalenecropsiesinLondon.JournalofPathologyandBacteriology,88,423-431.Hossain,S.,andHeard,B.E.(1970).Hyperplasiaofbronchialmuscleinchronicbronchitis.JournalofPathology,101,171-184.Leopold,J.G.,andGough,J.(1957).Thecentrilobularformofhypertrophicemphysemaanditsrelationtoc

hronicbronchitis.Thorax,12,219-235.Macleod,L.J.,andHeard,B.E.(1969).Areaofmuscleintrachealsectionsinchronicbronchitis,measuredbypoint-counting.JournaiofPathology,97,157-161.MedicalResearchCouncilCommittee(1975).Quantitativeassessmentofchronicnon-specificlungdiseaseatnecropsy.Thorax,30,241-251.Otto,H.(1970).DieAtmungsorgane.InHandbuchderallgemeinenPathologie,Bd.3,Teil4,pp.1-204.Springer,Berlin.Otto,H.(1971).DefinitionundMorphologiedesEmphysems.BeitragezurPathologie,142,221-228.Otto,H.,andRein,J.G.(1971).MorphologischeDefinitionundDiagnostikvonBronchiektasen.BeitragezurPathologie,143,70-83.Reid,L.(1960).Measurementofthebronchialmucousglandlayer:Adiagnosticyardstickinchronicbron-chitis.Thorax,15,132-141.Reid,L.(1967).ThePathologyofEmphysema.Lloyd-Luke,London.Restrepo,G.,andHeard,B.E.(1963a).Thesizeofthebronchialglandsinchronicbronchitis.JournalofPathologyandBacteriology,85,305-310.Restrepo,G.L.,andHeard,B.E.(1963b).Mucousglandenlargementinchronicbronchitis:extentofenlarge-mentinthetracheo-bronchialtree.Thorax,18,334-339.Restrepo,G.L.,andHeard,B.E.(1964).Airtrappinginchronicbronchitisandemphysema.AmericanReviewofRespiratoryDiseases,90,395-400.Ryder,R.C.,Thurlbeck,W.M.,andGough,J.(1969).Astudyofinterobservervariationintheassessmentoftheamountofpulmonaryemphysemainpaper-mountedwholelungsections.AmericanReviewofRespiratoryDisease,99,354-364.Spencer,H.(1977).PathologyoftheLung,3rdedition,Volume1,pp.130-149.PergamonPress,Oxford.Thurlbeck,W.M.,Dunnill,M.S.,Hartung,W.,Heard,B.E.,Heppleston,A.G.,andRyder,R.C.(1970).Acomparisonofthreemethodsofmeasuringemphysema.HumanPathology,1,215-226.Wyatt,J.P.(1959).Macrosectionandinjectionstudiesofemphysema.AmericanReviewofRespiratoryDiseases,L0(1),part2,94-103.Requestsforreprintsto:ProfessorB.E.Heard,Cardio-thoracicInstitute,BromptonHospital,FulhamRoad,LondonSW3,U