SECTION2 PULMONARY INFECTIOUS DISEASE.docx
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SECTION2 PULMONARY INFECTIOUS DISEASE.docx
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SECTION2PULMONARYINFECTIOUSDISEASE
SECTION2PULMONARYINFECTIOUSDISEASE
LiuZhong
一、PNEUMONIA
(一)GeneralConsideration
Pneumoniaisaninflammationofthedistalairways,alveoli,andinterstitiumofthelungthatcouldbeassociatedwithpathogenicmicroorganisms,physicalorchemicalagents,immunologicinjury,allergicdiseasesandmedicine.Thebacteriapneumoniaisthecommonestpneumoniaandalsotheoneofthecommonestinfectiousdisease.
(二)Epidemiology
Withanannualcostof$9.7billion,community-acquiredpneumonia(CAP)affects4millionadultsperyearintheUnitedStates,~20%ofwhomareadmittedtoahospitalfortreatment.Theoverallrateofpneumoniarangesfrom8to15per1000personsperyear,withthehighestratesattheextremesofageandduringthewintermonths.Themortalityofpneumoniainout-patientsislessthan1%~5%,12%inhospitalpatientsand40%inICUpatients.Theincreaseofmorbidityandmortalityofpneumoniaisassociatedwithageing,smoking,alcoholism,comorbidmedicalconditionsandimmunosuppression,suchaschronicobstructivepulmonarydisease(COPD),congestiveheartfailure,malignanttumour,diabetesmellitus,acquiredimmunedeficiencysyndrome(AIDS),applicationofimmunodepressantsandorgantransplantation.Furthermore,themutationofpathogenicmicroorganismsandabusageofantibioticsarealsopartiallyresponsible.
(三)Pathogenesis
Pulmonarydefencemechanisms(coughreflex,mucociliaryclearancesystem,immuneresponses)normallypreventthedevelopmentoflowerrespiratorytractinfectionsfollowingaspirationoforopharyngealsecretionscontainingbacteriaorinhalationofinfectedaerosols.Pneumoniaoccurswhenthereisadefectinoneormoreofthenormalhostdefencemechanismsorwhenaverylargeinfectiousinoculumsorahighlyvirulentpathogenoverwhelmsthehost.Pathogenicorganismscouldreachthelowerrespiratorytractandresultinpneumoniaviathefollowingways:
a.Aspirationofinfectedaerosols.
b.Disseminationviabloodstream.
c.Spreadingbytheadjacentorganinfections.
e.Aspirationofpermanentplantingorganismsintheupperairway.
f.Aspirationofgastric-oesophagealreflux.
(四)Classification
1.Anatomicalclassification
⑴Lobarpneumonia(alveolarpneumonia).StartwithalveolitisproducedbybacteriaandexpandtotheotheralveolithroughoutthelobeviatheporesofKohn,andresultsegmentsorevenwholelobeinfection.Atypicalcasehaspulmonaryparenchymainfectionandlobeconsolidationbutusuallythebronchuswillnotbeinvolved.Streptococcuspneumoniaeisthemainpathogen.X-rayfilmwillshowsegmentorlobarconsolidationshadow.
⑵Lobularpneumonia(bronchopneumonia).Pathogensspreadviabronchiandproduceinfectioninthebronchiole,distalbronchioleandalveoli.Bronchopneumoniaisoftensecondarytosomeotherdiseases,suchasbronchitis,bronchiectasis,upperairwayvirusinfectionandlong-termlyinginbedbecauseofseriousillness.ThecommonpathogensincludeStreptococcuspneumoniae,Staphylococci,viruses,Mycoplasmapneumoniaeandsoforth.Thereissecretionaccumulatedinthebronchiandsotheralescouldbeoftenheardbutnosignsofconsolidation.X-rayexaminationshowstheirregularpatchinfiltrationshadowsgoalongwiththelungmarkingsandnoappearanceofconsolidation.Lowerlobeiseasiertobeinvolved.
⑶Interstitialpneumonia.Interstitialpneumoniaisdefinedbyhistopathologicidentificationofaninflammatoryprocesspredominantlyinvolvingtheinterstitium,includingthealveolarwallsandtheconnectivetissuearoundthebronchovasculartree.Thealveolarseptacontainaninfiltrationoflymphocytes,macrophages,andplasmacells.Thealveolidonotcontainsignificantexudates,butprotein-richhyalinemembranessimilartothosefoundinadultrespiratorydistresssyndrome(ARDS).Itcouldbecausedbyinfectionofbacteria,mycoplasma,chlamydia,virus,pneumocystiscariniiandsoon.
2.Aetiologicalclassification
⑴Bacterialpneumonia.Accordingtothedifferentpathogenicbacterium,itcouldbeclassifiedasStreptococcuspneumoniae,Staphylococcusaureus,Alphahemolyticstreptococcus,Klebsiellapneumoniae,Hemophilusinfluenza,Pseudomonasaeruginosapneumoniaandsoforth.
⑵Atypicalpathogenspneumonia.Legionella,MycoplasmaandChlamydia.
⑶Viralpneumonia.Coronavirus,adenovirus,Respiratorysyncytialvirus,Influenzavirus,Measlesvirus,Cytomegalovirus,andHerpessimplexviruses.
⑷Fungalpneumonia.Candidaalbicans,Aspergillus,andActinomycetes.
⑸Otherpathogensassociatedpneumonia.Rickett'sorganism(Rickettsiaburneti),toxoplasmosis,protozoa(pneumocystiscarinii),andparasite(echinococcosispulmonum,endemichemoptysis,pulmonaryschistosomiasis).
⑹Physicalandchemicalpneumonia.Radiationpneumoniaassociatedwithradiotherapy,chemicalpneumoniabecauseofaspirationofgastricacid,andlipoidpneumoniaproducedbyaspirationoflipoidorassociatedwiththeinflammationproducedbyendogenouslipoid.
3.Classificationaccordingtothecircumstancesthepatientacquirepneumonia
⑴Community-acquiredpneumonia,CAPOccursoutsideofthehospitalorlessthan48hoursafteradmissioninapatientwhoisnothospitalizedorresidinginalong-termcarefacilityformorethan14daysbeforetheonsetofsymptoms.
A.Essentialsofdiagnosis
a.Symptomsandsignsofanacutelunginfection:
coughwithorwithoutpurulentsputum,dyspnea,withorwithoutchestpain.
b.Fever.
c.Bronchialbreathsoundsorralesarefrequentauscultatoryfindings.
d.WBC>10×109/Lor<4×109/L,withorwithoutshifttotheleft.
e.Parenchymalinfiltrationorinterstitialchangeswithorwithoutpleuraleffusiononchestradiograph.
Anyoneofthefirstfourpointsaboveplusthelastone,andexcludepulmonarytuberculosis,pulmonaryneoplasm,non-infectiouslunginterstitialdiseases,pulmonaryedema,atelectasis,pulmonaryembolism,pulmonaryeosinophiliaandpulmonaryvasculitis,thediagnosisofCAPcouldbeconfirmed.ThepathogensincludeStreptococcuspneumoniae,Hemophilusinfluenza,Moraxellecatarrhalis,andatypicalpathogens.
⑵Hospital-acquiredpneumonia,HAP/NosocomialPneumonia,NPOccursmorethan48hoursafteradmissiontothehospitalandexcludesanyinfectionpresentatthetimeofadmission.Ventilated-associatedpneumoniadevelopsinamechanicallyventilatedpatientmorethan48hoursafterintubation.
A.Essentialsofdiagnosis
a.Atleasttwoofthefollowing:
fever,cough,leukocytosis,purulentsputum.
b.Neworprogressiveparenchymalinfiltrateonchestradiograph.
c.Especiallycommoninpatientsrequiringintensivecareormechanicalventilation.
ThemostcommonorganismsresponsiblefornosocomialpneumoniainpatientswithouthighinfectionriskfactorsareStreptococcuspneumoniae,Hemophilusinfluenza,Staphylococcusaureus,Escherichiacoli,Klebsiellapneumoniaeandsoforth.Inpatientswithhighriskfactors,thecommonpathogensincludeStreptococcuspneumoniae,Pseudomonasaeruginosa,Enterobacter,Klebsiellapneumoniaeandsoforth.
(五)ClinicalFindings
Pneumoniacanrangeinseverityfrommildtofulminantandfatal,thiswilldependonthepathogen’svirulenceandthehost’scondition.Thetypicalpneumoniaischaracterizedbythesuddenonsetoffever,coughproductiveofpurulentorbloodysputum,withorwithoutpleuriticchestpain,shortnessofbreathordistress.Commonphysicalfindingsincludefever,tachypnea,tachycardia,nasalflaring,andcyanosis.Signsofpulmonaryconsolidationareoftenremarkableonchestexaminationwhenthereislobardistributionpneumonia.Dullnesstopercussionmaybedetectedifaparapneumonicpleuraleffusionorempyemaiscomplicated.
(六)DiagnosisandDifferentialDiagnosis
First,itisimportanttodifferentiatepneumoniafromupperrespiratorytractinfectionsandlowerrespiratorytractinfections.Theymayalsohavecough,feverthataresimilartothepneumonia,buttheyhavenoparenchymalinfiltrationsonthechestX-rayfilm.Secondly,otherdiseasesthatmimicthepneumoniashouldbeexcluded,whicharelistedasfollows:
1.Pulmonarytuberculosis
Patientswithpulmonarytuberculosisoftenhaveaninsidiousonsetandgeneraltoxicsymptoms,suchaslow-gradefever,nightsweat,fatigue,weightlostandsoforth.X-raywillpresentthecharacteristicchangesoftuberculosisthatincludeshadowsmainlylocatedintheupperzone,irregulardensity,slowdisappearance,cavityformationandbronchialdissemination.Sputumsmearfortuberclebacillicouldgetpositiveresultsandpatientswillnotrespondwelltothecommonantibiotictreatment.
2.Lungcancer
Pneumoniaisafrequentcomplicationofbronchialneoplasm,becauseofbronchialocclusion.Neoplasmmustbeexcludedinanypatientwhohaspneumoniawhichclearsslowlyradiologicallyorrepeatsinsamepartofthelung.FurtherinvestigationsincludeCT,MRI,bronchoscopyandsputumcytologicexaminationmayhelp.
3.Lungabscess
Theearlystagesymptomscouldbesimilarwithpneumoniabutlargeamountofpurulentsputumwillbecoughedupwhilethediseaseprogresses.X-rayshowscavitywithfluidlevelthatmakesiteasilybedifferentiatedfrompneumonia.
4.Pulmonarythromboembolism
Therearephlebothrombosisfactors,suchasthrombophlebitis,diseasesofheartandlung,trauma,surgery,neoplasmandsoforth.Hemoptysis,syncopeanddyspneaarethecharacteristicmanifestations.X-rayrevealsthatthereisalocallungmarkingdecreaseandsometimesawedgeshadow.Arterialbloodgasanalysisshowsahypoxemiaandhypocapnia.D-dimer,pulmonaryarteriographyCTscan,pulmonaryarteriography,radionuclidescanofventilationandperfusionandMRIcouldhelptodifferentiate.
5.Non-infectiouspulmonaryinfiltra
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