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PFO as a risk factor for Decompression Sickness. Dr Peter Germonpré, MD. SCUBA diving is BIG FUN. In Belgium, 35.000 divers are performing each 30-100 dives per year  1- 3.000.000 dives /yr Recreational SCUBA diving is BIG BUSINESS : Dive gear Dive schools Dive vacations.

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scuba diving is big fun
SCUBA diving is BIG FUN
  • In Belgium, 35.000 divers are performing each 30-100 dives per year 1- 3.000.000 dives /yr
  • Recreational SCUBA diving is BIG BUSINESS :
    • Dive gear
    • Dive schools
    • Dive vacations
scuba diving has it s risks
SCUBA Diving has it’s risks
  • … like any sport !
  • Risks associated with the underwater environment:
    • Drowning
    • Hypothermia
    • Animal life
    • Pressure-related disorders
saturation desaturation of inert gas
Saturation & desaturation of inert gas
  • Saturation = uptake (N2 = nitrogen) in tissues Desaturation = wash-out (N2) from tissues
  • Source = lungs = destinationVector = plasmaDestination = tissues = source
  • Dissolution Coefficients 
possible factors influencing saturation desaturation
Possible factorsinfluencing saturation (& desaturation)
  • Diffusion – related factors
    • Depth of dive ( alveolarN2 pressure )
    • Descent to which depth ( pressure gradient for N2)
    • Residual N2 pressure in tissue (from previous dive)
  • Perfusion – related factors
    • Dive time (time at depth)
    • Ascent speed
    • Cardiac output, vasoconstriction, personal (age, sex, health, VO2 Max…)
risk factors for dcs
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 in divers
Decompression Sickness in Divers
  • 30-50 cases per year in Belgium (overall risk = 1/40.000 dives)
  • 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%
haldane s work 1908
Haldane’s work (1908)

Pressure ratio of 2 / 1 = SafeStaged decompression = no DCS= no bubbles ?

decompression algorhythms12
Decompression Algorhythms
  • Are humans animals ?
slide14

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

slide16

Boyle’s Law

  • Growth of bubbles in tissue (Yount 1989)
  • Coalescence of bubbles

1 ATA

0.75 ATA

0.5 ATA

0.25 ATA

the foramen ovale
The Foramen Ovale
  • Fœtal circulation:
    • High MPAP
    • RAP > LAP
    • Fossa Ovalis
    • Valve-like structure
the foramen ovale20
The Foramen Ovale
  • Neonatal circulation:
    • Low MPAP
    • LAP > RAP
    • Fossa Ovalis
    • Valve-like structure
  • Closure in 5-10 days (in seal pups)
pfo related dcs the brain
PFO-related DCS & the Brain
  • 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
patent foramen ovale
Patent Foramen Ovale
  • Anatomical variant rather than disease
  • Prevalence:
  • 5-8mm long, 2-3mm wide
  • Valve-likestructure
slide25

Reversal of inter-atrial pressures

Vik et al., 1994 : Increase of MPAP during «bubbling» phase (>25%)

reversal of inter atrial pressures
Reversal of inter-atrial pressures

Balestra et al. 1998 (Undersea Hyperb Med)

retrospective studies 1
Retrospective studies (1)
  • 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
retrospective studies 2
Retrospective studies (2)
  • 1998: Germonpré et al. (J Appl Physiol) – c-TEE
    • 37 DCS divers (20 cerebral, 17 spinal)
    • 36 matched control divers (age, sex, BMI, smoking, physical fitness, diving experience)
    • semi-quantification of PFO (gr 0, 1, 2)
    • “undeserved DCS”
      • No diving technical errors
      • < 3 minor risk factors (fatigue, effort, alcohol, cold, dehydration,…)
standardised optimised c tee technique
Standardised, optimised c-TEE technique
  • Based on intrathoracic pressure changes
  • Strict protocol and sequence c-TEE

Balestra et al. Undersea Hyperb Med 1998; Germonpré et al. J Appl Physiol 1998

cerebral damage in divers
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
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
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 diving37
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
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
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)

pfo should every diver be screened
PFO : should every diver be screened ?
  • Causes of DCS
        • normal saturation - insufficient N2 off-gassing
        • increased saturation - “normal” off-gassing
        • increased saturation - insufficient off-gassing
        • normal saturation - “normal” off-gassing - clinical manifestation of “silent bubbles”
haldane s work
Haldane’s work

Pressure ratio of 2 / 1 = SafeStaged decompression = no DCS= no bubbles ?

re trospective studies risk quantification
Retrospective studies : risk quantification
  • Germonpré et al. 1998 (J Appl Physiol) – c-TEE :
    • Odds Ratio PFO – no PFO : 2.6
    • Odds Ratio PFO Gr 2 : 3.2
  • Bove et al. 1998 (Undersea Hyperb Med) - META :
    • Odds Ratio PFO : 2.5
    • Incidence of DCS in study population :2.28 / 10.000 dives
  • DAN 1989-1995 : DCS risk of «european diver»:
    • 1 / 7.390all dives (> 30m…)
    • 1 / 35.105no decompression dives < 30m
vascular bubble disease
Vascular bubble disease
  • Vascular bubble formation dependent on
    • Nitrogen load
    • Rate of ascent
    • Gas nuclei (endothelial cell pockets)
    • Nitrogen off-loading capacity of circulatory and pulmonary system (lung = bubble filter)
    • Cavitation at turbulence areas (heart valves)
    • Unknown factors
  • VGE : Venous Gas Embolism
feeling cold during decostops
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
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 – nitrix oxide (NO) or Heat Shock Protein (HSP) involved ?
slide48
Age
  • Aerospace medicine : age group of 40-45 yrs 3x more DCS than 20-25 yrs old
smoking
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
slide50

Detection Methods for PFODiTullio 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)

false negative c echo
False negative c-ECHO
  • Blood flow pattern SVC – IVC
  • Turbulences Sinus Venosus - RA
c tee gold standard
C-TEE : gold standard ?
  • C-Transthoracicechocardiography
    • 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 % !
re trospective studies 4
Retrospective studies (4)
  • Respiratory physiology: up to 12% anatomic venous-to-arterial 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 »
background
Background
  • Sports diving is a widely performed recreational activity: in Europe, more than 1.000.000 divers practice it regularly (>50 dives/year)
  • Decompression sickness (DCS) is caused by insufficient "off-gassing" (release of inert nitrogen gas after the dive)
  • Dive tables and computers can only predict the "safe" decompression speed and schedule with relative accuracy: other (unknown) factors play an often important role.
background56
Background
  • PFO = risk factor for DCS in sports diving (high-spinal, cerebral, “un-deserved”) (Germonpre et al., 1998; Bove et al., 1998)
  • To quantify the relative risk (RR),a prospective study is needed
  • A large number of divers (n>4000) would have to be screened and followed overa 5 year study periodin order to obtainstatistically valid results
gold standard for pfo detection contrast transesophageal echocardiography
“Gold Standard” for PFO detection :Contrast -Transesophageal Echocardiography
  • Time-consuming
  • Expensive equipment
  • Hospital-based
  • Invasive
  • Unpleasant
  • Standardised procedure absolutelyneeded to minimise false-positive or false-negative results !
      • Hagen (autopsy): ± 30% PFO
      • Various TTE, TCD & TEE studies: 16-47% !
screening technique ideal characteristics
Screening technique:“ideal” characteristics
  • Simple
  • Rapid
  • Low-cost
  • Minimally invasive
  • Safe
  • High specificity (few false positives)

Carotid Artery Doppler ?

carotid doppler technique
Carotid Doppler :technique
  • 8 MHz probe
  • NaCl perfusion
  • 2-syringe system
  • Straining manoeuvre
  • 3 injections 10cc
  • 10-15 minutes
carotid doppler
Carotid Doppler

Germonpré, Balestra et al. 1999

  • 33 patients (non-divers)
  • Comparison C-TEE vs CD
  • Prospective - blinded
  • False positives 3 / 11False negatives 0 / 22
  • Sensitivity 88 % - Specificity 100 %
  • Confirmed by independent French study on 160 patients (Cochard 1999)
carotid artery doppler
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
Carotid DopplerStudy
  • 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
a dan europe research protocol
a DAN Europe Research Protocol

Carotid Artery DopplerA prospective evaluation of the Risk of DCS in Divers with a Right-to-Left Shunt

  • Instructional Video
  • Information Webpage
  • Central Data Collection
  • Study Package for Divers
slide64

Carotid Artery DopplerA 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 > 10 countries (incl. Australia, 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
slide65

Divers Alert Network

  • Telephonic Emergency Consultation 24/24 Hotline: 0800-12382
      • Evaluation of case
      • Assisting evacuation
  • Research (PFO, Flying after Diving, Diabetics)
  • Training for Divers : Oxygen Provider Course, other courses
  • Internet: www.daneurope.org