It is well known that venous gas microemboli arecommonlydemonstratedafteruneventfuldiveswithoutany symptomsofDCI. It is alsowell known that in aconsiderablenumberofsubjects there isarterializationof thesemicroemboli,stillwithoutobvioussymptomsofDCI14,15).Neurologicalsymptomsandsignsareontheotherhandoften found in subjectswith joint or skinDCIwheretheneurological symptomsarenotdominant 16). Inherstudyoflongtermeffectsofdivinginsaturationdivers,Todnemetal. 17,18)demonstratedthat theprevalenceofneurological symptoms, signsandEEGpathologywasrelated toahistoryofDCI.Whencorrecting for that,therewasstillaneffectofcumulativedivingexposure.Later, perfusionMRI scanning has demonstratedperfusiondeficitsinthewater-shedareasofthebraininagroupofthesedivers19).

Other organ systems

Bone necrosis and its relationship to decompressionstressarewelldescribed.Long termeffectsofdivingonthevestibularsystemandhearinghasbeenreported,whichcouldbeduetodivingandexposuretonoise20,21).Acuteeffectson theaudio-vestibularsystem includingbarotraumashouldbewellknown.

Work related events and psychological stress

Divingoperationsaretechnicallycomplexandmaytakeplace in a rough environment. In a survey of formerNorthSeadivers,mosthadencounteredoneormorelife-threatening events during diving.The onesmostcommonly encountered were gas cut, entrapment/entanglementandproximitytofallingobjects.Twothirdsofthedivershadparticipatedinrecoveringdeadbodies.Severaleventswerelikelytocauseposttraumaticstressreactions as assessed by the Impact ofEventScale(IES-R)22).

Morbidity and mortality

Healthrelatedqualityof lifeasassessedwith theSF-36 questionnaire has been shown to be reduced informerNorthSeadiverswhowereprofessionallyactiveup to the 1990ies 23).The prevalence of respiratory,cardiovascularandneurologicaldiseasewas,however,not increased compared to the general population,but therewas an increased prevalence ofmusculo-skeletal and psychological symptoms. In a survey oftheNorwegiandivers included in the registry of theLabourInspectorate– includingmostof theNorwegianprofessionaldiversworking inshoreandoffshore (n＝5526) -overallmortalitywasnot increased.However,mortalityduetocardiovascular,cerebralandrespiratorydisease,andneoplasmswerelower,butmortalitydueto

招請講演Health effects of diving

EinarThorsen,MDPhDDepartmentofClinicalScience,UniversityofBergen,

andDepartmentofOccupationalMedicine,Haukeland

UniversityHospital,Bergen,Norway.

The diving exposure is complex.There are severalfactorsassociatedwithdiving thatmayhaveacuteandlong termhealtheffects.Effectsonbone, the lung, thecentralnervoussystem(CNS)havebeenandarestillofmajorconcern.

Alldives canbe characterizedby the simplephysicalparameterspressure,timeandgasmixture.Exposuretohyperoxia,decompressionstressandgasdensityarealldirectlyrelatedtothesephysicalfactorsirrespectiveofdivingmethods.Other factors thatarenotspecific fordivingsuchassubmersion, respiratoryheatandwaterlossandbreathingequipmentmayhaveadditionalhealtheffects,andenvironmental factorssuchaspollutionandworkrelatedpsychologicalstressmayposeanincreasedrisktothediver.

Effects of diving on the lung

Acuteeffectsofhyperoxia (oxygentoxicity),venousgasmicroembolism (decompression stress) and increasedrespiratory load (gasdensity,breathingequipment)havebeen extensively studied both experimentally and inrelation tooperationaldiving 1～5).Theacuteeffectsonthelungarewellcharacterizedandtheeffectsofsingleexposuresappeartobealmostfullyreversible.However,epidemiological studies, both cross-sectional 6～11) andlongitudinal12，13),indicatethatthereareresidualeffectsthatovertimeaccumulatetoalongtermeffect.Inmostof thesestudies therehasbeenarelationshipbetweencumulativedivingexposureand the rateofdecline inlungfunction.Physiologically, the longtermchanges inlungfunctionindiversareofanobstructivepattern.

Effects of diving on the central nervous system

Acuteeffectsofdivingon theCNSarerelated togasmixtureandcompressionrate,suchasnitrogennarcosisandthehighpressurenervoussyndrome.Theseeffectshave so farbeenconsidered fully reversible. It is theeffects of free gas and gasmicroembolism causingdecompressionillness(DCI)andthesequelaeofDCIthatareofconcern.Longtermsequelaecanbedemonstratedin 30-50%of subjects treated for neurologicalDCI.

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13）ThorsenE,SegadalK,KambestadB,GulsvikA.Pulmonaryfunctiononeandfouryearsafteradeepsaturationdive.ScandJWorkEnvironHealth1993;19:115-120.

14）Brubakk AO, Peterson R, Grip A, Holand B,OnarheimJ,SegadalK,KunkleTD,TønjumS.Gasbubbles in thecirculationofdiversafterascendingexcursions from300 to 250msw. JApplPhysiol1986;60:45-51.

15）LjubkovicM,ZanchiJ,BreskovicT,MarinovicJ,LojpurM,DujicZ.Determinants of arterial gasembolismafter scubadiving. JApplPhysiol2012;112:91-95.

16）Sundal E, GrønningM, Troland K, Irgens Å,AanderudL,ThorsenE.Riskofmisclassificationofdecompressionsickness.IntMaritMed2011;62:17-19.

17）TodnemK,NylandH,KambestadBK,Aarli JA.Influence of occupational divingupon the nervoussystem:anepidemiologicalstudy.BrJIndMed1990;47:708-714.

18）TodnemK,SkeidsvollH,SvihusR,RinckP,RiiseT,KambestadBK,Aarli JA.Electroencephalography,evokedpotentialsandMRIbrainscansinsaturationdivers.Anepidemiologicalstudy.ElectroencephalogrClinNeurophysiol1991;79:322-329.

19）MoenG,SpechtK,TaxtT,SundalE,GrønningM,ThorsenE,TrolandK,IrgensÅ,GrünerR.Cerebraldiffusionandperfusiondeficits inNorthSeadivers.ActaRadiol2010;51:1050-1058.

20）MolværOI,AlbrektsenG.Hearingdeterioration inprofessionaldivers:anepidemiologicstudy.UnderseaHyperbMed1990;17:231-246.

21）Goplen FK, Grønning M , I rgens A , Sunda lE , Norda h l SH . Ve s t ibu la r s ympt oms a ndotoneurological findings inretiredoffshoredivers.AviatSpaceEnvironMed2007;78:414-419.

22）Troland K, Sundal E, Irgens A, GrønningM,Thorsen E. Potentially traumatic events andposttraumatic stress reactions in retiredNorthSeadivers. XXXVIIth annualmeetingofEuropeanUnderseaBiomedicalSociety,Gdansk2011(abstract).

23）IrgensÅ,GrønningM,TrolandK,SundalE,NylandH,ThorsenE.Reduced health related quality oflife in formerNorthSeadivers isassociatedwithdecompressionsickness.OccupMed2007;57:349-354.

24）IrgensÅ, TrolandK, ThorsenE,GrønningM.Mortality among professional divers inNorway.OccupMed2013;63（8）:537-43.

accidentsandsuicidewashigherwhencomparedto thegeneralmalepopulationofthesameage24).Thisfindingis of concernwith respect to the high prevalence ofadverseeventsandtraumaticexperiencesduringdivingwhichmaycauseposttraumaticstressreactions.

References

1）ThorsenE,SegadalK,ReedJW,ElliottC,GulsvikA,HjelleJO.Contributionofhyperoxia to reducedpulmonary function after deep saturation dives. JApplPhysiol1993;75:657-662.

2）SuzukiS.Probablelunginjurybylong-termexposuretooxygenclose to50kilopascals.UnderseaHyperbMed1994;21:235-243.

3）ThorsenE,HjelleJ,SegadalK,GulsvikA.Exercisetolerance and pulmonary gas exchange after deepsaturation dives. JApplPhysiol 1990; 68: 1809 -1814.

4）DujicZ,ObadA,PaladaI,ValicZ,BrubakkAO.Asingleopenseaairdive increasespulmonaryarterialpressure and reduces right ventricular function inprofessionaldivers.EurJApplPhysiol2006;97:478-485.

5）ThorsenE,SkogstadM,ReedJW.Subacuteeffectsof inspiratory resistive loading andhead-outwaterimmersiononpulmonary function.UnderseaHyperbMed1999;26:137-141.

6）ThorsenE,SegadalK,KambestadB,GulsvikA.Divers'lungfunction:smallairwaysdisease?BrJIndMed1990;47:519-523.

7）TetzlaffK,FriegeL,ReuterM,HaberJ,MutzbauerT, Neubauer B. Expiratory f low limitation incompressedairdiversandoxygendivers.EurRespirJ1998;12:895-9.

8）AdirY,ShupakA,LaorA,Weiler-RavellD.Largelungsindivers:naturalselectionoratrainingeffect?Chest2005;128:224-228.

9）WattS.Effectof commercialdivingonventilatoryfunction.BrJIndMed1985;42:59-62.

10）DmitroukAI,GulyarSA,IlyinVN,MoiseenkoEV.Physiologicalmechanisms of adaptation of diversto the conditionofdeepwater in theantarctic. In:Proceedingsof16thannualmeetingof theEuropeanUnderseaBiomedicalSociety(SterkW,GeeraedtsL,eds),Amsterdam1990:311-9.

11）Suzuki S, Thorsen E . Long term effects ofsaturationdivingonpulmonaryfunction–reductioninFEF50%andFEF75%inearlyperiodofdivingcareer.XXVIIIthannualmeetingofEuropeanUnderseaBiomedicalSociety,Brugge,2002(abstract).

12）SkogstadM,ThorsenE,HaldorsenT,KjuusH.Lungfunctionoversixyearsinprofessionaldivers.OccupEnvironMed2002;59:629-633.

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日本高気圧環境・潜水医学会雑誌 Vol.48（4）,Dec,2013