Transcript Patent Foramen Ovale as a cause of Decompression Sickness

PFO as a risk factor for
Decompression Sickness
a DAN Europe Research Programme
[email protected]
SCUBA Diving has it’s risks
… like any sport !
Risks associated with the underwater
environment:
–
–
–
–
Drowning
Hypothermia
Animal life
Pressure-related disorders
Decompression Sickness in Divers
Overall risk (DAN Europe data):
– 1 / 7.390 all dives (> 30m…)
– 1 / 35.105 no decompression dives < 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%
Risk factors for DCS
Depth – Time profile – Repetitive dives
Reverse dive profiles
Speed of ascent
Exercise during dive
Cold during deco stops
Personal habits : poor physical condition, smoking, age
Personal factors : fat content, dehydration, alcohol use,
sex
..... ?
Decompression Sickness : the cause
Decompression Algorhythms
Saturation & desaturation
of inert gas
Saturation = uptake (N2 = nitrogen) in tissues
Desaturation = wash-out (N2) from tissues
Source = lungs = destination
Vector = plasma
Destination = tissues = source
Dissolution Coefficients 
Water
Fat
H2
0,017
0,036
He
0,009
0,015
N2
0,013
0,067
Ar
0,027
0,140
Haldane’s work (1908)
Pressure ratio of
2 / 1 = Safe
Staged
decompression
= “no DCS”
No bubbles ?
Comex data base (JP Imbert)
Risk of
DCS
15
10
Time
5
120
90
60
0
57
60
5
54
51
45
48
42
36
39
20
30
33
24
27
18
21
12
15
30
Depth
DAN Europe: analysis of 202 cases of DCS
1989-1993
Depth > 30 msw
Deco diving
Error ascent / stops
Repetitive dive
Stress – Fatigue
Multiday diving
Material fault
Altitude after dive
Decompression Sickness : the cause
Boyle’s Law
Growth of bubbles in tissue (Yount 1989)
Coalescence of bubbles
10msw
5msw
2msw
surface
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
(>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. orthodeoxiaplatypnea 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 disease
Prevalence: Author
1 – 20 yrs
20-40 yrs
> 40 yrs
Patten 1931
34.5%
27.2%
22.4%
Hagen 1984
35%
29%
20.4%
5-8mm long, 2-3mm wide
Valve-like
structure
Transthoracic echocardiography
Trans-oesophageal echo
C-TEE
PFO-related DCS
1989: Moon et al. (Lancet) : c-TTE
– PFO 37% in DCS divers
– PFO 61% in neurologic DCS
– PFO 10.7% in non-divers
1989: Wilmshurst et al. (Lancet) : c-TTE
– PFO 66% in early neurologic DCS
– PFO 17% in late neurologic DCS (30 min)
– PFO 24% in control divers
PFO-related DCS
Germonpré et al. 1998 (J Appl Phys) (c-TEE) :
– Significant association PFO – cerebral DCS
– No association PFO – Spinal DCS
Louge et al. 2001 (Crit Care Med) (c-TCD) :
– Cerebral DCS: 83% TCD pos
– Spinal DCS:
37.9% TCD pos
Torti et al. 2004 (Undersea Hyperb Med) (c-TEE) :
– > cerebral / vestibular symptoms
Risk Quantification :
Germonpré et al. 1998 (J Appl Physiol) – c-TEE :
– Odds Ratio PFO – no PFO :
– Odds Ratio PFO Gr 2 :
2.6
3.2
Bove et al. 1998 (Undersea Hyperb Med) - META :
– Odds Ratio PFO : 2.5
DCS risk of «european diver»:
– DAN 1989-1995 :
• 1 / 7.390 all dives (> 30m…)
• 1 / 35.105 no-decompression dives < 30m
– BSAC 2004:
• 1 / 10.500 dives (mostly deeper than 30msw, cold dives)
Cardiac echography
after a 25m/25min. dive
Reversal of inter-atrial pressures
Bubble load and duration
Vik et al., 1994 :
Increase of MPAP
during «bubbling»
phase (>25%)
Feeling cold during decostops
Leffler et al. Aviat Space Env Med 2001 : increased risk for DCS
when divers are warm throughout the dive
Marroni 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 1999
High VO2max (= good fitness)  less post-dive bubbles
Wisloff et al. J Physiol 2004
Exercise 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 OR
Wilmshurst 2001 : smokers more likely for DCS-AGE
Venous inflow increase in the heart
Balestra et al. 1998 (Undersea Hyperb Med)
Not all R-L shunts are a PFO !
Respiratory physiology: up to 12% anatomic venous-toarterial pulmonary shunting
Sulek et al. (Anesthesiology 1999) : c-TEE + c-TCD
– Cerebral embolisation of fat emboli after TKA
– after important emboli afflux (tourniquet release)
– (even without PFO) : opening of intrapulmonary shunts
Cardiology practice c-TEE :
– If bubbles observed after more than 3 (5) heartbeats after
appearance in RA  « pulmonary passage of bubbles »
Cerebral damage in divers
Adkisson et al. 1989 (Lancet) (SPECT):
– Cerebral perfusion deficit after neurologic DCS & AGE
Knauth et al. 1997 (Lancet) (RNM)
(87 divers):
– Multifocal cerebral lesions
• 7 lesions in 7 divers without PFO
• 34 lesions in 4 divers with PFO grade 2
• Total (TCD) 25 divers PFO, 13 grade 2
– Auto-selection of divers : ?
Nitrogen bubble embolisation may cause
cerebral ischemic damage in divers ?
Diver S. - 39 years old - 17 years diving experience - 800+
dives
1 confirmed episode of vestibular / cerebellar decompression
sickness - timely treated & completely recovered
Anamnesis: > 10 episodes of abnormal drowsiness, fatigue during approx. 1 hour, after dives
Brain Damage through diving ?
Reul et al., Fueredi et al.,
Knauth et al.
WEAK POINTS :
Selection bias : DCS ?
Morphological (MR)
analysis : Wirchow
spaces ?
PFO detection method :
other shunts ?
Brain Damage through diving ?
Selection bias : DCS ?
– 200 volunteer divers:
• Age < 40 yrs
• > 5 yrs diving, > 200 dives
• No history of DCS
– Random ¼ selection
Morphological (MR) analysis: Wirchow spaces ?
– T1, T2, FLAIR sequences: diff diagnosis
PFO detection method : other shunts ?
– Standardised c-TEE
Neuropsychometric testing: WAIS, MMS subtests for
neurotoxic solvents
Results
– In experienced divers who never had DCS,
no increased prevalence of WML is found
as compared to a control population
– In these divers, a high prevalence of PFO
is found (65%)
(Germonpré et al. EUBS Congress 2003)
Time-related opening
of PFO in divers
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)
Detection Methods for PFO
DiTullio et al. 1993 - Kerut et al. 1997
c-TEE
Transcranial Doppler (c-TCD)
– Sensitivity 68% to 90% - Specificity 100%
Transthoracic Echocardiography (c-TTE)
– Sensitivity 47% - Specificity 100%
Right Heart Catheterisation
– Sensitivity 80% - Specificity 100%
(Di Tullio et al: Stroke 1993 - Kerut et al.: Am J Cardiol 1997)
C-TEE : gold standard ?
C-Transthoracic echocardiography
– 10 – 18 %
(Lynch et al. 1984, Van Hare et al. 1989)
C-Trans-oesophageal echocardiography
– Konstadt et al. 1991: 26 %
– Fisher et al. 1995: 9.2 %
– Meissner et al. 1999: 25.6 %
Anatomical prevalence : 25-30 % !
False negative c-ECHO
Blood flow pattern SVC – IVC
Turbulences Sinus Venosus - RA
Prospective study
To quantify the relative risk (RR) of PFO in diving, a
prospective study is needed
A large number of divers (n>4000) would have to be
screened and followed over a 5 year study period in
order to obtain statistically valid results
–
–
–
–
Test all divers
Do not inform them of the result
Let them dive « at leisure »
Collect data and evaluate after a total of 200.000 dives
Screening technique:
“ideal” characteristics
Simple
Rapid
Low-cost
Minimally invasive
Safe
High specificity
(few false positives)
Carotid Artery
Doppler ?
Carotid Doppler :
technique
8 MHz probe
NaCl perfusion
2-syringe system
Straining manoeuvre
3 injections 10cc
10-15 minutes
Carotid Doppler
Germonpré, Balestra et al. 1999
33 patients (non-divers)
Comparison C-TEE vs CD
Prospective - blinded
False positives 3 / 11
False negatives 0 / 22
Sensitivity 88 % - Specificity 100 %
Confirmed by independent French
study on 160 patients
(Cochard 1999)
Carotid Artery Doppler
Simple : Yes - easy to learn
Rapid : Yes - 15 minutes
Low-cost : Yes
Minimally invasive : Yes
Safe : better than C-TEE
Sensitivity : 100 %
Suitable for screening on a large scale :
prospective study on RR of PFO
Carotid Doppler
Study
Data collection in volunteer
divers
– European scale (4000+ divers needed based
on a 2.5 x increased DCS risk)
– Blinded to the result
– Instructed on “safe diving” (ethical committee)
– Dynamic follow-up (research card, website)
– Follow-up period: 5-6 years
Carotid Artery Doppler
A prospective evaluation of the Risk of DCS in Divers with a Right-to-Left Shunt
Multicentric study, start : January 2003
Divers Alert Network support: participation of > 5 countries
(incl. South Africa)
Recruitment of divers through DAN publications,
investigator effort
Safety of saline contrast injection
Precautions: oxygen on-site, no diving 24 hours before CD
Informed consent form
Divulgation of results: DAN publications, international journals
Carotid Artery Doppler
A prospective evaluation of the Risk of DCS in Divers with a Right-to-Left Shunt
a DAN Europe Research Protocol
Instructional Video
Information Webpage
Central Data Collection
Study Package for Divers