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1、 Dyspnea Definition DyspneaisdefinedasanawarenessofdifficultyinbreathingItisthereforeasymptom usuallydescribedbythepatientas shortofbreath whetherthesensationisduetoactualdifficultyinbreathingorisessentiallyanawarenessofhyperventilation Ifthesymptombecomesstriking italwayscompanieswithdilatationofna
2、res cyanosis useofaccessorymusclesofrespirationandabnormalitiesofrespiratoryrate depthorrhythm RespiratorydiseasesCirculatorydiseasesPoisoningHematologyNeuropsychogenicfactors Etiology Respiratorydyspnea Causedbyabnormalventilationandgasexchange reductioninventilatorycapacity hypercapniaandhypoxemia
3、resultingfromrespiratorydisease Threeclininaltypes InspiratorydyspneaExpiratorydyspneaMixeddyspnea Inspiratorydyspnea Tendstooccurprimarilywhenthereisobstruction suchasinflammation edema tumorandforeignbody inlarynx tracheaandmajorbronchi Characterizedbythedepressionsigh inwhichvisibleindrawingovert
4、hesternalnotch thesupraclavioularspaces theintercostalspacesandtheepigastriumintheinspirationcanbeseen Oftenaccompaniedbyacoarse lowpitchedinspiratorywheezinganddrycough Expiratorydyspnea Expiratorydyspneaisduetothedecreaseoflungelasticityandspasmnarrowingofthebronchiolesandsmallerbronchiasinemphyse
5、ma bronchialasthmaandasthmaticbronchitis Expirationisprolongedandlabouredwithwheezing Mixeddyspnea Occurswiththeextensivelungdisease suchasseverepneumonia pulmonaryfibrosis massiveatelectasis pleuraleffusionandpneumothorax Resultsinthedecreaseofventilatorsandgasexchangecapacity Breathingisdifficultd
6、uringbothinspirationandexpiration Cardiacdyspnea Cardiacdyspneaisusuallyattributabletopulmonaryvascularcongestionresultingfromtheleftand orrightheartfailure Cardiacdyspnea InLeft sidedheartfailure complianceisreduced andtherefore ventilationisdecreasedtotheedematouslungregionsandvitalcapacityreduced
7、 Alveoliarestiffandmoreworkisneededtoovercomeelasticrecoil thehighalveolarpressurewillstimulatestretchreceptorandinitiatetheinflationreflexresultinginearlyturningoffofinspirationandanincreaseinrespiratoryrate Cardiacdyspnea Thedyspneacausedbyright sidedheartfailureislessseverethanthatonecausedbyleft
8、 sided Mechanism 1 Thepressureofrightatrialandsuperiorvenacavaisthenaturalstimulusofrespiratorycenter 2 Thedecreaseofoxygencontentandtheaccumulationoftheacidmetabolites suchaslactic stimulaterespiratorycenter 3 Therestrictionoftherespiratorymovementcausedbyenlargementofliverresultingfromcongestion a
9、scitesandpleuraleffusion Cardiacdyspnea Symptomsofcongestiveheartfailurecancauseorthopneaandparoxysmalnocturnaldyspneawhenelevated fillingpressureispresent orthopnea Orthopneaisdifficultyinbreathinginthesupineposition thismayberelivedbysittingup whichreducesthedegreeofpulmonarycongestionbypoolingblo
10、odinthelowerextremitiesandloweringleftventricularfillingpressures improvingthediaphragmaticmovement increasingvitalcapacity paroxysmalnocturnaldyspnea Symptoms Thepatientawakesshortofbreathatnight butoftenobtainreliefbysittingupforaperiodoftime Inthemostadvancedcases thepatientsbecomeacutelydyspneic
11、 cyanoticandveryfrequentlyproducefoamysputumtingedwithblood Signs Moistralesatthebothlungbases tachycardia wheezingandbronchospasm themarkedlyaccentuatedsecondheartsoundinthepulmonicarea Mechanism Supinepostureforsleepresultsinresorbtionofextracellularfluidintotheintravascularspace causingariseinfil
12、lingpressure Theparoxysmaldyspneaistermedascardiacasthma Itcanbeseeninthehypertensiveheartdiseaseandcoronaryheartdisease paroxysmalnocturnaldyspnea Toxicdyspnea Inthemetabolicacidosis uremiaanddiabeticketosis theacidmetabolitesstimulatetherespiratorycenter causingdeepandregularrespirationwithsnoring
13、 TheoverdoseofmorphineandpentobarbitalcandepressrespiratorycentercausingdeeprespirationorCheyne Stokessrespiration Neuro Psychogenicdyspnea Inpatientssufferingfromcerebrovasculardiseases intracranialhemorrhage elevatedintracerebralpressure therespiratorycenterlosesthebloodsupplyoriscompressed Theres
14、pirationbecomesdeep slowandirregular Insomecasesthedyspneamaybepsychogenic whichischaracterizedbyrepetitivedeep sighingrespirationwithnumbnessofextremitiesorlips cheiropedalspasm Thesearealsomanifestationsofacutehypocapniaandrespiratoryalkalosis Hematologicaldyspnea Insevereanemia sulfhemoglobinemia
15、 methaemoglobinemiaorcarbonmonoxidepoisoningthedecreaseofoxygen carryingcapacityandoxygencontentdevelopabnormalrespirationandincreasedheartrate Therespirationratealsoincreasesinshockwhichstimulatesrespirationcenterbecauseofhypotension AccompaniedSymptomParoxysmaldyspneawithwheezing Dyspneawithchestp
16、ain Dyspneawithfever Dyspneawithcoughandpurulentsputum Dyspneawithcoma ParoxysmaldyspneawithwheezingItispresentinbronchialasthmaandcardiacasthma Paroxysmalseveredyspneaisoftenseeninacutelarynxedema foreignbodyinbronchi massivepulmonaryembolism andspontaneouspneumothorax Dyspneawithchestpain Itisfrequentlyobservedinlobarpneumonia pulmonaryinfarction spontaneouspneumothorax acuteexudativepleurisy acutemyocardialinfarction andbronchialcarcinoma Dyspneawithfever Itiscommonlynotedinpneumonia lungabsc
