肥胖低通氣綜合征麻醉

JiajiaMaEdmondH.L.Chau,M.D.Anesthesiology,July2012;117:188–205ObesityHypoventilationSyndromeAReviewofEpidemiology,Pathophysiology,andPerioperativeConsiderations幾張圖片幾個概念OHS睡眠呼吸暫停綜合癥上氣道阻力綜合癥單純性鼾癥正常人OSAHS單純性鼾癥：夜間可出現(xiàn)不同程度鼾癥，AHI<5次/h，白天無癥狀。上氣道阻力綜合征：夜間可出現(xiàn)不同頻度、程度鼾癥，雖上氣道阻力增高，但AHI<5次/h，白天嗜睡或疲勞，試驗性無創(chuàng)通氣治療有效。OSAHS：睡眠時上氣道塌陷阻塞引起的呼吸暫停和通氣不足、伴有打鼾、睡眠結(jié)構(gòu)紊亂，頻繁發(fā)生血氧飽和度下降、白天嗜睡等病癥。AHI:睡眠時患者平均每小時發(fā)生的呼吸暫停（>10s)以及低通氣次數(shù)。用于評價患者OSAHS嚴重程度和治療效果的最重要指標。幾個概念I(lǐng)ntroductionObesityhypoventilationsyndrome(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(醋酸甲羥孕酮片)acetazolamide（乙酰唑胺）。目前文獻報道較少，療效不是十分確切，不推薦作為主要治療措施。PerioperativeManagementofPatientswithOHS

HowDoWeScreenforOHSinthePreoperativeSetting?

Threeclinica