肥胖低通气综合征麻醉

JiajiaMaEdmondH.L.Chau,M.D.Anesthesiology,July2012;117:188–205ObesityHypoventilationSyndromeAReviewofEpidemiology,Pathophysiology,andPerioperativeConsiderations几张图片几个概念OHS睡眠呼吸暂停综合症上气道阻力综合症单纯性鼾症正常人OSAHS单纯性鼾症：夜间可出现不同程度鼾症，AHI<5次/h，白天无症状。上气道阻力综合征：夜间可出现不同频度、程度鼾症，虽上气道阻力增高，但AHI<5次/h，白天嗜睡或疲劳，试验性无创通气治疗有效。OSAHS：睡眠时上气道塌陷阻塞引起的呼吸暂停和通气不足、伴有打鼾、睡眠结构紊乱，频繁发生血氧饱和度下降、白天嗜睡等病症。AHI:睡眠时患者平均每小时发生的呼吸暂停（>10s)以及低通气次数。用于评价患者OSAHS严重程度和治疗效果的最重要指标。几个概念IntroductionObesityhypoventilationsyndrome(OHS)：

ObesityDaytimehypoventilationSleep-disorderedbreathingWithoutanalternativeneuromuscular,mechanical,ormetaboliccauseofhypoventilationIntroductionTherapyObjectiveToexaminetheprevalenceofOHS;Reviewthecurrentdataondiseasemechanisms,screening,andtreatment;DiscusstheoptimalperioperativemanagementofOHS.MaterialsandMethodsprevalenceandtreatmentofpatientswithOHS.OHSwasdefinedasDaytimehypercapniaandhypoxemia(PaCO2>45mmHgandPaO2<70mmHg)Obesepatients(BMI>30kg/m2)Sleep-disorderedbreathingAbsenceofanyothercauseofhypoventilation.WhatIsthePrevalenceofOHS?OSApatientsbariatricsurgicalpatientssleeplaboratorygeneraladultpopulationWhataretheMechanisms?

DaytimehypercapniaLeptinResistanceLeptinisaproteinproducedspecificallybytheadiposetissuethatregulatesappetite,energyexpenditure,andincreasesventilationforthecarbondioxideproduction.AssociatedwithBMI.Leptinleveldropsafterpositiveairwaypressure(PAP)therapy.ThepathogenesisofchronicdaytimehypoventilationofOHSIncreasedMechanicalLoadandImpairedRespiratoryMechanics

ObesityBMIImpairedCompensationofAcuteHypercapniainSleep-disorderedBreathing

HyperventilationduringbriefperiodsofarousalChronichypercapniainOHSWhenapneasbecomethreetimeslongerthanthebreathinginterval,CO2accumulates.AreduceddurationofventilationduringapneaAgradualadaptationofchemoreceptorssecondarytomildelevationofserumHCO3-.DoPatientswithOHSPossessDifferentClinicalFeaturesthanObesePatientswithEucapnia?SignificantlyhigherBMI,increasedhypoxemiaandhypercapnia,morerestrictiverespiratorymechanics,andmoreseveresleep-disorderedbreathing.More……UpperAirwayObstructionBoththesittingandsupinepositionRespiratoryMechanicsExcessiveload,Chestwallcompliance,pulmonaryresistance--doubletheworkofbreathingCentralRespiratoryDriveResultfromleptinresistanceandsleep-disorderedbreathingPulmonaryHypertensionSecondarytochronicalveolarhypoxiaandhypercapniaishigherinpatientswithOHS,rangingfrom30%to88%.DoPatientswithOHSExperienceHigherMorbidityandMortalitythanObesePatientswithOSAandComparableBMI?

Morelikely

todevelop……Especially……Previoushistoryofvenousthromboembolism,morbidobesity,malesex,hypertension,increasingage,andnoncompliancewithPAPtreatmentmayfurtherincreasemortalityrisk.Surgicalmortalityrateinhigh-riskOHSpatientsundergoingbariatricsurgeryisbetween2–8%.WhatIstheMainstayofTherapy?

PAPTherapy:Short-termandLong-termBenefits

CPAPandbi-levelPAP.Short-termbenefitsincludeanimprovementingasexchangeandsleep-disorderedbreathing.AsignificantdecreaseinPaCO2,increaseinPaO2.AsignificantimprovementinAHIandoxygensaturationduringsleep.Long-termbenefitsofPAPincludeanimprovementingasexchange,lungvolumes,andcentralrespiratorydrivetocarbondioxide,pulmonaryfunction(FEV1和FVC).PAPmayalsoreducemortalityinOHS.PAPisconsideredthefirst-linetherapyforOHS.Bothshort-termandlong-termpositiveairwaypressuretherapyincreasePaO2anddecreasePaCO2inpatientswithOHS.Bothshort-termandlong-termpositiveairwaypressuretherapyimproveAHIandoxygensaturationduringsleepinpatientswithOHS.Long-termpositiveairwaypressuretherapyimprovesFEV1,FVC,andCO2sensitivityinpatientswithOHS.EfficacyofBilevelPAPversusCPAP

WhenCPAPfailure,definedbyaresidualAHI>5orameannocturnalSpO2<90%,ThesecanbeimprovedwithbilevelPAP.BilevelPAPwasnotconsiderablysuperiortoCPAP,ifCPAPtitrationwassuccessful.SupplementalOxygenApproximately40%ofpatientswithOHScontinuetodesaturatetoSpO2_90%duringsleepwhileonadequateCPAPsettings,therebyrequiringsupplementaloxygen.Thelowestconcentration,particularlyinOHSexperiencinganexacerbationorrecoveringfromsedatives/narcoticsorgeneralanesthesia.WeightReductionSurgery1yraftersurgery,BMI,AHI,PaO2,PaCO2,FEV1,andFVCallimprovedsignificantly.AlthoughthereisadrasticreductioninOSAseverity,somepatientsstillhavemoderateOSA--stillrequirePAPtherapyafterweightloss.Pharmacotherapymedroxyprogesteroneacetate(醋酸甲羟孕酮片)acetazolamide（乙酰唑胺）。目前文献报道较少，疗效不是十分确切，不推荐作为主要治疗措施。PerioperativeManagementofPatientswithOHS

HowDoWeScreenforOHSinthePreoperativeSetting?

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