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SCUBA Diving has it’s risksSCUBA Diving has it’s risks
… like any sport !Risks associated with the underwater environment:– Drowning– Hypothermia– Animal life– Pressure-related disorders
Overall risk (DAN Europe data):– 1 / 1 / 7.3907.390 all dives (> 30m…)all dives (> 30m…)– 1 / 1 / 35.10535.105 no decompression divesno decompression dives < 30m < 30m
Dive profile errors : 40% normal saturation - insufficient off-gassing
“Logical” causes of decompression failure : 20%increased saturation - “normal” N2 off-gassing
increased or normal saturation - insufficient off-gassing
“Unexplained” : 40%
Decompression Sickness in Divers
Risk factors for DCS
Depth – Time profile – Repetitive divesReverse dive profilesSpeed of ascentExercise during diveCold during deco stopsPersonal habits : poor physical condition, smoking, agePersonal factors : fat content, dehydration, alcohol use, sex..... ?
Decompression Sickness : the cause
Decompression Algorhythms
Saturation = uptake (N2 = nitrogen) in tissues Desaturation = wash-out (N2) from tissues
Source = lungs = destinationVector = plasmaDestination = tissues = source
Dissolution Coefficients H2 He N2 Ar Water 0,017 0,009 0,013 0,027 Fat 0,036 0,015 0,067 0,140
Saturation & desaturation of inert gas
Haldane’s work (1908)
Pressure ratio of 2 / 1 = Safe
Staged decompression = “no DCS”
No bubbles ?
Comex data base (JP Imbert)
12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60
5
20
30
60
90
120
0
5
10
15
Risk ofDCS
Depth
Time
DAN Europe: analysis of 202 cases of DCS DAN Europe: analysis of 202 cases of DCS 1989-19931989-1993
Depth > 30 mswDepth > 30 msw
Deco divingDeco diving
Error ascent / stopsError ascent / stops
Repetitive diveRepetitive dive
Stress – FatigueStress – Fatigue
Multiday divingMultiday diving
Material faultMaterial fault
Altitude after diveAltitude after dive
Decompression Sickness : the cause
Growth of bubbles in tissue (Yount 1989)Coalescence of bubbles
10msw 5msw 2msw surface
Boyle’s Law
The Decompression Sickness « Grey Zone »
Mechanism of disease
Causes of right-to-left shunting
Functional shunts– Opening of intrapulmonary shunts:
pulmonary artery pressure increase due to embolisation of nitrogen bubbles (Vik et al., 1994 : Increase of MPAP during «bubbling» phase Vik et al., 1994 : Increase of MPAP during «bubbling» phase (>25%))(>25%))
– Bubble recompression (yo-yo diving at end of dive)
Causes of right-to-left shunting
Anatomical shunts– Intrapulmonary shunts (congenital)– Extrapulmonary shunts (acquired; e.g. orthodeoxia-
platypnea syndrome)– Intracardiac shunts: patent foramen ovale
The Foramen Ovale
Fœtal circulation:– High MPAP– RAP > LAP– Fossa Ovalis– Valve-like structure
The Foramen Ovale
Neonatal circulation:– Low MPAP– LAP > RAP– Fossa Ovalis– Valve-like structure
Closure in 5-10 days (in seal pups)
Mechanism of disease
Patent Foramen Ovale
Anatomical variant rather than diseasePrevalence:
5-8mm long, 2-3mm wideValve-likestructure
Author 1 – 20 yrs 20-40 yrs > 40 yrs
Patten 1931 34.5% 27.2% 22.4%
Hagen 1984 35% 29% 20.4%
Author 1 – 20 yrs 20-40 yrs > 40 yrs
Patten 1931 34.5% 27.2% 22.4%
Hagen 1984 35% 29% 20.4%
Transthoracic echocardiography
Trans-oesophageal echo
C-TEE
PFO-related DCS1989: Moon et al. (Lancet) : 1989: Moon et al. (Lancet) : c-c-TTTTEE– PFOPFO 37% 37% in DCS diversin DCS divers– PFO PFO 61% 61% in neurologic DCSin neurologic DCS– PFO PFO 10.7% 10.7% in non-diversin non-divers
1989: Wilmshurst et al. (Lancet) : 1989: Wilmshurst et al. (Lancet) : c-c-TTTTEE– PFOPFO 66% 66% in early neurologic DCSin early neurologic DCS– PFOPFO 17% 17% in late neurologic DCSin late neurologic DCS (30 min) (30 min)– PFOPFO 24% 24% in control diversin control divers
Germonpré et al. 1998 Germonpré et al. 1998 (J Appl Phys(J Appl Phys)) (c-TEE)(c-TEE) ::– Significant association PFO – cerebral DCSSignificant association PFO – cerebral DCS– No association PFO – Spinal DCSNo association PFO – Spinal DCS
Louge et al. 2001 (Crit Care Med)(Crit Care Med) (c-TCD)(c-TCD) : :– Cerebral DCS: 83% TCD posCerebral DCS: 83% TCD pos– Spinal DCS: 37.9% TCD posSpinal DCS: 37.9% TCD pos
Torti et al.Torti et al. 2004 2004 ((Undersea Hyperb Med) Undersea Hyperb Med) (c-TEE)(c-TEE) ::– > cerebral / vestibular symptoms> cerebral / vestibular symptoms
PFO-related DCS
Germonpré et al. 1998 Germonpré et al. 1998 (J Appl Physiol)(J Appl Physiol) – – c-TEEc-TEE : :– Odds Ratio Odds Ratio PFO – no PFOPFO – no PFO : : 2.62.6– Odds Ratio Odds Ratio PFOPFO Gr 2 : Gr 2 : 3.23.2
Bove et al. 1998 Bove et al. 1998 (Undersea Hyperb Med)(Undersea Hyperb Med) - META : - META :– Odds Ratio Odds Ratio PFOPFO : 2.5 : 2.5
DCS risk of «european diver»DCS risk of «european diver»: : – DAN 19DAN 1989-199589-1995 : :
• 1 / 1 / 7.3907.390 all dives (> 30m…)all dives (> 30m…)• 1 / 1 / 35.10535.105 no-decompression divesno-decompression dives < 30m < 30m
– BSAC 2004:BSAC 2004:• 1 / 10.500 dives (mostly deeper than 30msw, cold dives)1 / 10.500 dives (mostly deeper than 30msw, cold dives)
Risk Quantification :Risk Quantification :
Cardiac echography after a 25m/25min. dive
Reversal of inter-atrial pressuresReversal of inter-atrial pressures
Bubble load and durationBubble load and duration
Vik et al., 1994 : Vik et al., 1994 : Increase of MPAP Increase of MPAP during «bubbling» during «bubbling» phase (>25%)phase (>25%)
Feeling cold during decostops
Leffler et al. Aviat Space Env Med 2001 : increased risk for DCS when divers are warm throughout the diveMarroni et al. EUBS Meeting 2001 : increased and prolonged bubble production when skin temperature was cold in end-stage of dive
Physical condition
Carturan – J Appl Physiol 1999High VO2max (= good fitness) less post-dive bubbles
Wisloff et al. J Physiol 2004Exercise at 20 hrs before dive prevents bubbles in rats – nitrox oxide (NO) or Heat Shock Protein (HSP) involved ?
Age
Aerospace medicine : age group of 40-45 yrs 3x more DCS than 20-25 yrs old
Smoking
HSE Report 2003 : smoking by itself not significant for DCS; lung function alteration 2x higher ORWilmshurst 2001 : smokers more likely for DCS-AGE
Balestra et al. 1998 (Undersea Hyperb Med)Balestra et al. 1998 (Undersea Hyperb Med)
Venous inflow increase in the heartVenous inflow increase in the heart
Respiratory physiology: up to 12% anatomic venous-to-Respiratory physiology: up to 12% anatomic venous-to-arterial pulmonary shuntingarterial pulmonary shuntingSulek et al. (Anesthesiology 1999) : c-TEE + c-TCDSulek et al. (Anesthesiology 1999) : c-TEE + c-TCD– Cerebral embolisation of fat emboli after TKACerebral embolisation of fat emboli after TKA– after important emboli afflux (tourniquet release) after important emboli afflux (tourniquet release) – (even without PFO) : opening of intrapulmonary shunts(even without PFO) : opening of intrapulmonary shunts
Cardiology practice c-TEE :Cardiology practice c-TEE :– If bubbles observed after more than 3 (5) heartbeats after If bubbles observed after more than 3 (5) heartbeats after
appearance in RA appearance in RA « pulmonary passage of bubbles » « pulmonary passage of bubbles »
Not all R-L shunts are a PFO !Not all R-L shunts are a PFO !
Cerebral damage in divers
Adkisson et al. 1989 (Lancet) (SPECT):Adkisson et al. 1989 (Lancet) (SPECT):– Cerebral perfusion deficit after neurologic DCS & AGECerebral perfusion deficit after neurologic DCS & AGE
Knauth et al. 1997 (Lancet) (RNM)Knauth et al. 1997 (Lancet) (RNM) (87 divers):(87 divers):– Multifocal cerebral lesions Multifocal cerebral lesions
• 7 lesions in 7 divers without PFO7 lesions in 7 divers without PFO• 34 lesions in 4 divers with PFO grade 234 lesions in 4 divers with PFO grade 2• Total (TCD) 25 divers PFO, 13 grade 2Total (TCD) 25 divers PFO, 13 grade 2
– Auto-selection of divers : ?Auto-selection of divers : ?
Diver S. - 39 years old - 17 years diving experience - 800+ divesDiver S. - 39 years old - 17 years diving experience - 800+ dives
1 confirmed episode of vestibular / cerebellar decompression sickness - timely treated & 1 confirmed episode of vestibular / cerebellar decompression sickness - timely treated & completely recoveredcompletely recovered
Anamnesis: > 10 episodes of abnormal drowsiness, fatigue - during approx. 1 hour, after Anamnesis: > 10 episodes of abnormal drowsiness, fatigue - during approx. 1 hour, after divesdives
Nitrogen bubble embolisation may cause cerebral ischemic damage in divers ?
Nitrogen bubble embolisation may cause cerebral ischemic damage in divers ?
Brain Damage through diving ? Brain Damage through diving ?
Reul et al., Fueredi et al., Reul et al., Fueredi et al., Knauth et al.Knauth et al.
WEAK POINTSWEAK POINTS : :Selection bias : DCS ?Selection bias : DCS ?Morphological (MR) Morphological (MR) analysis : Wirchow analysis : Wirchow spaces ?spaces ?PFO detection method : PFO detection method : other shunts ?other shunts ?
Brain Damage through diving ? Brain Damage through diving ? Selection bias : DCS ?Selection bias : DCS ?
– 200 volunteer divers:200 volunteer divers:• Age < 40 yrsAge < 40 yrs• > 5 yrs diving, > 200 dives> 5 yrs diving, > 200 dives• No history of DCSNo history of DCS
– Random ¼ selectionRandom ¼ selection
Morphological (MR) analysis: Wirchow spaces ?Morphological (MR) analysis: Wirchow spaces ?– T1, T2, FLAIR sequences: diff diagnosisT1, T2, FLAIR sequences: diff diagnosis
PFO detection method : other shunts ?PFO detection method : other shunts ?– Standardised c-TEEStandardised c-TEE
Neuropsychometric testing: Neuropsychometric testing: WAIS, MMS subtests for neurotoxic solventsWAIS, MMS subtests for neurotoxic solvents
Results
– In experienced divers who never had DCS, In experienced divers who never had DCS, no increased prevalence of WML is found no increased prevalence of WML is found as compared to a control populationas compared to a control population
– In these divers, a high prevalence of PFO In these divers, a high prevalence of PFO is found (65%)is found (65%)
(Germonpré et al. EUBS Congress 2003)(Germonpré et al. EUBS Congress 2003)
Initial PFO prevalence:– 14/33 PFO (42.5%) – 5 Gr.1 - 9 Gr.2
Final PFO prevalence:– 17/33 PFO (51.5%) – 3 Gr.1 - 14 Gr.2
PFO grades:– Gr.0 Gr.1 : 3 /19 divers– Gr.0 Gr.2 : 1 /19 divers– Gr.1 Gr.2 : 4 / 5 divers– Gr.1 Gr.0 : 1 / 5 divers
(Germonpré et al. Am J Cardiol 2005)
Time-related opening of PFO in divers
Detection Methods for PFODetection Methods for PFODiTullio et al. 1993 - Kerut et al. 1997DiTullio et al. 1993 - Kerut et al. 1997
c-c-TEETEE
TranscrTranscraaninialal Doppler (c- Doppler (c-TCDTCD))– SensitivitSensitivityy 68% 68% toto 90% - Specificit 90% - Specificityy 100% 100%
TransthoracTransthoracicic Echocardiograph Echocardiographyy (c-TT (c-TTEE))– SensitivitSensitivityy 47% - Specificit 47% - Specificityy 100% 100%
Right Heart Right Heart CatheterisationCatheterisation– SensitivitSensitivityy 80% - Specificit 80% - Specificityy 100% 100%
(Di Tullio et al: Stroke 1993 - Kerut et al.: Am J Cardiol 1997)(Di Tullio et al: Stroke 1993 - Kerut et al.: Am J Cardiol 1997)
C-TEE : gold standard ?
C-C-TransthoracicTransthoracic echocardiographyechocardiography– 10 – 18 %10 – 18 %
(Lynch et al. 1984, Van Hare et al. 1989)(Lynch et al. 1984, Van Hare et al. 1989)
C-Trans-oesophageal echocardiographyC-Trans-oesophageal echocardiography– Konstadt et al. 1991: 26 %Konstadt et al. 1991: 26 %– Fisher et al. 1995: 9.2 %Fisher et al. 1995: 9.2 %– Meissner et al. 1999: 25.6 %Meissner et al. 1999: 25.6 %
Anatomical prevalence : 25-30 % !Anatomical prevalence : 25-30 % !
False negative c-ECHO
Blood flow pattern SVC – IVCTurbulences Sinus Venosus - RA
Prospective study
To quantify the relative risk To quantify the relative risk ((RR) of PFO in diving,RR) of PFO in diving, a a prospective study is neededprospective study is neededA large number of divers (n>4000) would have to be A large number of divers (n>4000) would have to be screened screened and followed and followed overover a 5 year study perioda 5 year study period in order to in order to obtainobtain statistically valid resultsstatistically valid results– Test all diversTest all divers– Do not inform them of the resultDo not inform them of the result– Let them dive « at leisure »Let them dive « at leisure »– Collect data and evaluate after a total of 200.000 divesCollect data and evaluate after a total of 200.000 dives
Screening technique:Screening technique:“ideal” characteristics“ideal” characteristics
SimpleSimpleRapidRapidLow-costLow-costMinimally invasiveMinimally invasiveSafeSafeHigh specificity High specificity (few false positives)(few false positives)
Carotid Artery Carotid Artery Doppler ?Doppler ?
Carotid Doppler :Carotid Doppler : techniquetechnique
8 MHz probe8 MHz probeNaCl perfusionNaCl perfusion2-syringe system2-syringe systemStraining manoeuvreStraining manoeuvre3 injections 10cc3 injections 10cc
10-15 minutes10-15 minutes
Carotid Doppler Carotid Doppler
33 patients 33 patients ((non-non-divers)divers)Comparison Comparison C-TEE vs CDC-TEE vs CDProspective - Prospective - blindedblinded
FaFalselse positi positiveves 3 / 11s 3 / 11FaFalselse n neegatigativeves 0 / 22s 0 / 22
SensitivitSensitivityy 88 % - Sp 88 % - Speecificitcificityy 100 % 100 %
Confirmed by independent French study on 160 Confirmed by independent French study on 160 patients patients (Cochard 1999)(Cochard 1999)
Germonpré, Balestra et al. 1999Germonpré, Balestra et al. 1999
Carotid Artery DopplerCarotid Artery Doppler
Simple : Yes - easy to learnSimple : Yes - easy to learnRapid : Yes - 15 minutesRapid : Yes - 15 minutesLow-cost : YesLow-cost : YesMinimally invasive : YesMinimally invasive : YesSafe : better than C-TEESafe : better than C-TEESSensitivensitivity : 100 %ity : 100 %
Suitable for screening on a large scale : Suitable for screening on a large scale : prospective study on RR of PFOprospective study on RR of PFO
Carotid DopplerCarotid DopplerStudy Study
Data collection in volunteer Data collection in volunteer diversdivers– European scale (4000+ divers needed based European scale (4000+ divers needed based
on a 2.5 x increased DCS risk)on a 2.5 x increased DCS risk)– Blinded to the resultBlinded to the result– Instructed on “safe diving” (ethical committee)Instructed on “safe diving” (ethical committee)– Dynamic follow-up (research card, website)Dynamic follow-up (research card, website)– Follow-up period: 5-6 yearsFollow-up period: 5-6 years
Multicentric study, start : January 2003Multicentric study, start : January 2003Divers Alert Network support: participation of > 5 countries (incl. South Divers Alert Network support: participation of > 5 countries (incl. South Africa)Africa)Recruitment of divers through DAN publications, Recruitment of divers through DAN publications, investigator effortinvestigator effortSafety of saline contrast injectionSafety of saline contrast injectionPrecautions: oxygen on-site, no diving 24 hours before CDPrecautions: oxygen on-site, no diving 24 hours before CDInformed consent formInformed consent formDivulgation of results: DAN publications, international journalsDivulgation of results: DAN publications, international journals
Carotid Artery DopplerCarotid Artery Doppler A prospective evaluation of the Risk of DCS in Divers with a Right-to-Left ShuntA prospective evaluation of the Risk of DCS in Divers with a Right-to-Left Shunt
a DAN Europe Research Protocola DAN Europe Research Protocol
Instructional VideoInstructional VideoInformation Webpage Information Webpage Central Data CollectionCentral Data CollectionStudy Package for DiversStudy Package for Divers
Carotid Artery DopplerCarotid Artery Doppler A prospective evaluation of the Risk of DCS in Divers with a Right-to-Left ShuntA prospective evaluation of the Risk of DCS in Divers with a Right-to-Left Shunt
