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Divers are taught some basic physiology during their training. There is therefore some underlying knowledge and understandable concern in the diving community about the presence of a patent foramen ovale (PFO) as a cause of decompression illness (DCI). There is an agreement that PFO screening should not be done routinely on all divers; however, when to screen selected divers is not clear. We present the basic physiology and current existing guidelines for doctors, advice on the management and identify which groups of divers should be referred for consideration of PFO screening. Venous bubbles after diving and right to left shunts are common, but DCI is rare. Why this is the case is not clear, but the divers look to doctors for guidance on PFO screening and closure; both of which are not without risks. Ideally, we should advise and apply guidelines that are consistent and based on best available evidence. We hope this guideline and flow chart helps address these issues with regard to PFOs and diving.
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REVI E W Open Access
Patent foramen ovale and scuba diving: a
practical guide for physicians on when to refer
for screening
Oliver Sykes
1*
and James E Clark
2
Abstract
Divers are taught some basic physiology during their training. There is therefore some underlying knowledge and
understandable concern in the diving community about the presence of a patent foramen ovale (PFO) as a cause
of decompression illness (DCI). There is an agreement that PFO screening should not be done routinely on all
divers; however, when to screen selected divers is not clear. We present the basic physiology and current existing
guidelines for doctors, advice on the management and identify which groups of divers should be referred for
consideration of PFO screening. Venous bubbles after diving and right to left shunts are common, but DCI is rare.
Why this is the case is not clear, but the divers look to doctors for guidance on PFO screening and closure; both
of which are not without risks. Ideally, we should advise and apply guidelines that are consistent and based on
best available evidence. We hope this guideline and flow chart helps address these issues with regard to PFOs
and diving.
Keywords: Patent foramen ovale, Decompression illness, Arterial gas embolism, Screeni ng
Review
Introduction
Decompression illness (DCI) encompa sses decompres-
sion sickness (DCS) and arterial ga s embolism (AGE).
The differentiation of the pathological processes in prac-
tice can be difficult, but the treatment is similar; hence,
both are given the mod ern overarching term of decom-
pression illness. DCS occurs as a result of venous bub-
bles forming in the tissues and vessels, which can cause
mechanical, embolic and biochemical effects with mani-
festations ranging from trivial to fatal [1]. AGE is caused
by arterial bubbles as a result of ruptured lung alveoli
from gas trapping in the lungs or blood shunting from
the venou s right atrial side to the arterial left atrial side
of the heart. This is known as a right to left shunt.
Symptoms usually appear short ly after, or within 30 min
of surfacing, but can have delayed onset. These symp-
toms are frequently neurological in nature [2-4] and can
be profound. The lungs are an effective filter, and a right
to left shu nt, such as a patent foramen ovale (PFO), is
therefore a route for bubbles to avoid this filter and
enter the arterial system. This is known as a paradoxical
embolism and is depicted in Figure 1. Usually, the blood
pressure on the arterial left side is higher than the ve-
nous right, which prevents right to left flow. However,
this pressure differential is reversed on releasing a Valsalva
manoeuvre, causing the right atrium to fill before the left
atrium. Unfortunately, 30 to 60 min post-dive is the peak
time for bubble liberation [5], which coincides with divers
climbing into boats, lifting heavy kit, straining and uncon-
sciously performing Valsalva manoeuvres.
In the fetus, the foramen ovale is vital to allow blood
to bypass the lungs, which are not in use. On breathing
at birth, there is a flap valve effect [6] (Figure 2), and the
negative intra-thoracic pressure helps closes this route.
While in about 30% there remains a leak, DCI is still a
rare event [1,7]. This suggests that not all divers with a
PFO are at increased risk of DCI [8]. However, those
that are susceptible appear to get the more serious
neurological symptoms. Moon examined 91 patients
with a two-dime nsional echocardiogram, who were eva-
luated and/or treated for DCS at Duke University
* Correspondence: o.sykes@nhs.net
1
London Hyperbaric Medicine, Whipp's Cross University Hospital, London E11
1NR, UK
Full list of author information is available at the end of the article
© 2013 Sykes and Clark; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
Sykes and Clark Extreme Physiology & Medicine 2013, 2:10
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Medical Center. Of these 91, 39 had a PFO and 64 of
the 91 had more serious symptoms (weakness, dizziness
or symptoms of brain abnormalities); 32 of these 64 had a
PFO [9] (50%). The risk of DCI by right to left shunting is
related to the tissu e nitrogen load (i.e . pressuretime
profile), the size and characteristics of the shunt and the
presence of other factors likely to cause right to left
shunting [10,11]. These include occult lung disease,
smoking, lung shunts, Vals alva, straining and functional
size of the PFO. According to Dr. Peter Wilmshurst,
cardiologist of the UK Sport s Diving Medical Commit-
tee, the requirement s for shunt-mediated D CI are a
large right to left shunt, a PFO, atrial septal defe ct or
pulmonary arteriovenous lung malformation, a dive pro-
file that liberates venous bubbles profile and also an
appropriate inert ga s load in critical tissue to amplify
embolic bubbles [12].
Divers are taught some basic physiology during their
training. There is therefore some underlying knowledge
and understandable concern in the popular diving press
about the presence of a PFO as a cause of DCI [9,13,14].
Unfortunately, DCI can occur after any dive, even within
the depths and time limits of tables and computers, and
after the diver has made many hundreds of dives without
incident. All divers experiencing problems after diving
should consult a diving physician, to whom this guide-
line is aimed. A list of contact details can be found at
www.uksdmc.co.uk. Even when performin g dives which
are inside acceptable and safe decompression algorithms,
venous bubbles are very common [2,15,16], and the Di-
vers Alert Network states that:
While 2030 percent of divers might be expected to
have a PFO, decompression illness (DCI) in
recreational divers occurs after only 0.005-0.08
percent of dives, clearly much lower than the one in
five or six that might be expected if every diver with a
PFO and venous bubbles developed DCI. Based on
current experience, the estimated risk of a DCI
incident characteristic of those correlated with PFO is
between 0.002-0.03 percent of dives [17].
Therefore, routine screening of all divers for a PFO is
not warranted primarily because the absolute risk of
neurological DCI is low and the cost of screening is high
[1], and bey ond the recommendation not to screen all
divers , there are no clear guidelines on when to screen
for PFOs in divers who may be at risk of shunt-mediated
Pulmonary
Vein
Left
Atrium
Left Ventricle
Right Ventricle
Pulmonary
Artery
Right Atrium
To the
body
To the Lungs
A
o
r
t
a
Right Atrium
To the
body
To the Lungs
Aorta
PFO
A
B
J
.
C
l
a
r
k
Figure 1 Paradoxical gas embolism. Schematic drawing
demonstrating the paradoxical gas embolism in a diver with a PFO
(A); migration of a bubble of gas from the venous system to the left
atrium via a PFO, with subsequent systemic embolisation (B).
Figure 2 Intra-cardiac echocardiogram. Showing the patent
foramen ovale, in an adult and in real time, acting as a flap valve
between the right atrium (RA) and left atrium (LA) [6].
Sykes and Clark Extreme Physiology & Medicine 2013, 2:10 Page 2 of 7
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DCI. Here, we present a practical approach to a com-
mon problem of what to do with a diver who may war-
rant or request a referral for a PFO check. These are
guidelines for doctors treating divers and should not be
used in place of diver training.
Current guidelines
According to the UK Sports Diving Medical Committee [18]:
Approximately one quarter of the population have a
patent foramen ovale or a small atrial septal defect, but
the risk of paradoxical embolism is much greater in
those with large shunts [10,19]. Decompression illness
is very unusual in sport divers after dives to less than 20
metres and we have not observed neurological
decompression illness that appears to be the result of
paradoxical embolism in sport divers after dives to that
depth. We have observed neurological decompression
illness associated with a large shunt in a professional
diver who did a working dive at 18 m, which required
in-water stops that were performed correctly. It
therefore seems reasonable that sport divers known to
have intra-cardiac shunts should be allowed to dive
shallower than 15 m, provided no other cardiac contra
indications exists. If a diver with a shunt wishes to go
deeper than 15 m the options include use of nitrox with
an air decompression table (to reduce bubble liberation
and tissue nitrogen load) and the use of a table such as
the DCIEM (Defence and Civil Institute of
Environmental Medicine) table which is believed to
result in little or no bubble nucleation. It will also be
possible for some individuals to return to unrestricted
diving after trans-catheter closure of the defect.
For commercial divers, the Health and Safety Execu-
tive (HSE) state that [20]:
Examination for the presence of an intra-cardiac
shunt is not a requirement for either the initial or the
annual examination. However, examination for patent
foramen ovale should be performed in a diver who
has suffered neurological, cutaneous or cardio-
respiratory decompression illness, particularly where
there is a history of migraine with aura or where the
dive profile was not obviously contributory, since it
may contribute to an assessment of the overall risk to
the diver of continu ing to dive. A positive finding is
not necessarily a reason for a finding of unfitness.
However, the opinion of a cardiologist with an interest
in diving medicine is recommended.
The National Institute of Clinical Excellence (NICE)
has produced guidelines on the closure of PFOs in di-
vers, [21] which also emphasises the importance of
involving a cardiologist knowledgeable in diving medi-
cine. The assessment of the presence and size of a PFO
can be poor and can therefore lead to people getting in-
appropriate advice and being put at risk. The Undersea
and Hyperbaric Medical Societ y (UHMS) Best Practise
Guidelines [22] state that PFO testing may be considered
after severe or repetitive neurological D CS and may help
in advising divers to modify their di ve profiles. Carl
Edmond's Diving Medic ine [23] agrees that the risk from
a PFO is not great enough for it to be appropriat e to test
all divers, and repair of the hole is probably more dan-
gerous than diving with it.
When to refer
There should probably be different advices for different
divers , and we will cover the following categories, based
on the current standard operating procedure at London
Hyperbaric Medicine: (a) no DCI, (b) one episode of
DCI, (c) more than one episode of DCI, (d) migraines
and (e) commercial divers.
No decompression illness
If the diver has not had DCI, discourage the diver from
seeking a PFO check. However, consider what the reason
for the request might be. Divers often deny symptoms of
DCI but worry they may have a PFO. No diving is the only
way to guarantee no DCI. Consider also the expense,
worry, risk and the possible impact on medical insurance.
If concerned about a PFO and the diver wants to continue
diving, encourage safe diving practices (Figure 3). A diver's
safest profile is a rapid descent to the deepest part of the
dive with a gradual ascent, whereas a reverse profile dive
is one where the diver spends a prolonged time at the
shallowest part of the dive before going deeper for the lat-
ter part of the dive. A reverse profile dive maximises nitro-
gen uptake during the dive and results in a greater risk of
bubble formation and, consequently, DCI following as-
cent. If the diver wants to dive outside these recommen-
dations, then suggest referral to a cardiologist with an
interest in diving.
One episode of DCI
Discuss whether the diver want s to continue diving,
despite being susceptible to D CI. If the diver wants to
continue diving, encourage safe diving practices and
decide whether there are any factors suggestive of a
PFO (Figure 4). If any factors are present , then have a
lowerthresholdforPFOcheck.Ifthedivewaspro-
vocative (Figure 5) and the re were no other factors,
then encourage safe diving practices and not a PFO
check. There is no re commendation to che ck for a
PFO after all types of D CI.
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More than one episode of DCI
As with divers after one episode of DCI, discuss whether
the diver wants to continue diving, despite being suscep-
tible to DCI. If the diver wants to continue diving, en-
courage safe diving practices (Figure 3) and have a lower
threshold for screening for a PFO. If the diver clearly
understands the risks and agrees to dive to less than 15
m, then no PFO check is necessary. However, the diver
may have unrealistic views on what makes a safe dive,
and these cases can be difficult. Use the DCIEM [24] or
British Sub-Aqua Club 1988 decompression tables [25]
to prove whether the dive profiles are relatively safe, al-
though DCI can still occur within these tables. A PFO
check with a cardiologist with an interest in diving can
also be useful in these cases, as this will allow a realistic
discussion of the risks of continuing to dive with the
diver's cardiac status, as per the UHMS Best Practise
Guidelines [22]. We would therefore suggest that a PFO
check is discussed with the diver.
Migraines
Divers with migraine with aura are at increased risk of
neurological DCI [26-28]. However, we should encourage
safe diving practices (Figure 3) and check whether the
medications are appropriate for diving. There is no rec-
ommendation to screen for a PFO in divers simply with
Figure 3 Safe
diving practices. Courtesy of London Hyperbaric Medicine.
Figure 4 Factors suggestive of a PFO. Courtesy of London
Hyperbaric Medicine.
Figure 5 Provocative
dive profile. Courtesy of London Hyperbaric Medicine.
Figure 6 Guidewire and patent foramen ovale occluder device
(courtesy of St. Jude Medical).
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migraines with aura. However, those with migraines with
aura and at least one episode of DCI should probably have
a PFO check. Diagnosing migraine with aura is important
as migraine without aura and other headaches are not
considered a risk factor for DCI or having a PFO.
Commercial divers
Commercial divers could be defined as those requiring
an HSE Commercial Diving Medical for their work.
These divers cannot modify their dive profiles and have
very clear inc entives to continue diving; therefore, stop-
ping diving or encouraging safe diving is not a realistic
option. Check whether there are any factors suggestive
of a PFO and follow the HSE guidelines above [20].
Referral, screening and closure
Guidelines for screening for PFOs are difficult to cre-
ate be cause the relationship between PFOs and DCI is
not clear and also be cause D CI is rare and most of the
tests involve e xpense, worry and some risk. Cardiac in-
vestigations a re not always of sufficient quality to pick
up all right to left shunts such as pulmonary arterio-
venous malformations. There are als o a number of
ways of testing for a PFO, which may explain why the
rates vary. De ciding when to check for and close a
PFO can also be difficult but ultimately lies with the
cardiologist performing the proce dures. PFO checks
and closures are done at many centres , but screening
and advice on continued diving must come from a car-
diologist with an interest in diving.
Figure 7 Intra-cardiac echocardiography. The guidewire and
catheter can be seen in the heart, passing from the right atrium (RA),
through the patent foramen ovale, into the left atrium (LA). The
bright white area (echo dense) on the wall of the LA opposite the RA
is the occlude device with the guidewire attached [29].
Figure 8 Flow chart on when to refer for screening by a cardiologist with an interest in diving. Courtesy of London Hyperbaric Medicine.
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The screening procedure
A small dose of bubbles is injected into a large ante-
cubital fossa vein, and the diver is asked to perform a
Valsalva. Since bubbles show up well on ultrasound,
there is then opacification of the right atria and ven-
tricle, and any bubbles that traverse the septum can be
easily seen. As far as we know, there have been no
reported problems after the dose of intravenous bubbles.
The closure procedure
This is performed using a local anaesthetic and sed-
ation, or general anaesthesia, and can be done a s a day
case. A guidewire and catheter (Figure 6) are inserted
through a vein usua lly in t he groin into the heart
and through the PFO using imaging guidance [29]
(Figure 7). A device is then inserted via the catheter,
closing the hole. There is a NICE guidance on Percu-
taneous closure of patent foramen ovale for the second-
ary prevention or recurrent paradoxical embolism in
divers (issued December 2010) [21]. In terms of effi-
cacy and risks, the guidance for patients includes five
studies with a total of 1,2 83 patient s who had the pro-
cedure for a number of different conditions; the PFO
was immediately closed in 1,268 patients (99%) [30]
and a further study of 29 divers treated by the proced-
ure for neurological de compression sickne ss : 23 had
returned to diving and experie nced no more de com-
pression sickness and 6 were not diving (three as they
had only recently had the procedure and three for re a-
sons unrelated to the procedure) [30]. In terms of risks
and possible problems, the NICE guidance is useful
again [30]:
In a study of 280 patients, cardiac tamponade was
reported in 2 patients (0.71%) who both required
further surgery.
In 2 studies with a total of 992 patients, the device
used to close the PFO caused a tear in a large blood
vessel of the heart requiring emergency surgery in 1
patient (0.10%). The device fell out and entered the
circulation in 7 patients (0.71%).
Abnormal heart rhythm during or after surgery was
reported in 13 of 95 patients (13.68%) in 2 studies
of a total of 213 patients.
As well as looking at these stu dies, NICE also
asked expert advisers for their views who said
that in theory, a problem with the heart va lves
could occ ur.
It is worth emphasising that the risk post-closure of
DCI returns to normal and not zero. The closure also
requires checking with repeat echocardiography to en-
sure closure and a period of antiplatelet therapy which
must be completed before returning to diving.
Conclusions
Venous bubbles after diving and right to left shunts are
common, but DCI is rare. Why this is the case is not
clear, but the divers seek doctors' guidance on PFO
screening and closure, both of which are not without
risks. Ideally, we should advise and apply guidelines that
are consistent and based on best available evidence. We
hope this guideline and flow chart (Figure 8) help ad-
dress these issues with regard to PFOs and diving.
Abbreviations
DCI: Decompression Illness; DCIEM: Defence and Civil Institute of
Environmental Medicine; HSE: Health and Safety Executive; NICE: National
Institute of Clinical Excellence; PFO: Patent foramen ovale; UHMS: Undersea
and Hyperbaric Medical Society.
Competing interests
JEC is a lecturer in Aerospace and Applied Physiology at King's College,
London and runs the B.Sc. Extreme Physiology and M.Sc. in Human
Physiology in Extreme Environments and a diving medicine module. OS is
paid as a doctor at the hyperbaric unit at Whipp's Cross Hospital and, as part
of this work, refers divers for PFO checks.
Authors' contributions
Both authors (JEC and OS) have made substantive intellectual contributions
in conceiving, designing, interpreting, drafting and revising the manuscript
critically for important intellectual content and have given final approval of
the version to be published. Notably, OS conceived the idea and provided
the guideline at London Hyperbaric Medicine. JEC advised on changes to
the guidelines and produced graphics. Both authors read and approved the
final manuscript.
Authors' information
OS is currently a senior registrar in anaesthetics in SW London, a PADI
Divemaster and a hyperbaric doctor at Whipp's Cross University Hospital,
where there are over 100 cases of DCI every year. Some are referred for PFO
screening. The guideline for referral of divers for a PFO check was developed
by OS in order to help other doctors at the unit refer appropriate cases. OS
also writes regularly for Sport Diver and contributes to the discussions on the
UK Sport Diving Medical Committee forum, where PFO screening is a
common theme. JEC is a lecturer and independent researcher at King's
College, London within the Centre for Human Aerospace Physiological
Sciences and the Cardiovascular Division, respectively. He teaches on the M.
Sc. in Human & Applied Physiology programme and undergraduate
physiology courses including Human Physiology in Extreme Environments
(MSc) and Extreme Physiology (BSc) in diving medicine. He is a British Sub-
Aqua Club advanced diver and instructor.
Acknowledgements
The authors would like to thank London Hyperbaric Medicine for the use of
the guideline: Referral of Divers for PFO Check.
Author details
1
London Hyperbaric Medicine, Whipp's Cross University Hospital, London E11
1NR, UK.
2
Centre of Human & Aerospace Physiological Sciences, King's
College, London SE1 1UL, UK.
Received: 1 July 2012 Accepted: 11 January 2013
Published: 1 April 2013
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doi:10.1186/2046-7648-2-10
Cite this article as: Sykes and Clark: Patent foramen ovale and scuba
diving: a practical guide for physicians on when to refer for screening.
Extreme Physiology & Medicine 2013 2:10.
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... 5 22 Physiologically, Valsalva manoeuvres performed shortly after surfacing may explain the temporal presentation of AGE soon after diving in individuals with highgrade PFO. 23 However, the association between PFO and DCI and whether PFO closure reduces the risk of DCI remains controversial. 23 In an important study of experienced divers (N=230) by Torti and colleagues, 24 the risk of significant DCI was 4.8-fold to 12.9-fold higher in those with PFO detected by transoesophageal echocardiography, and risk was further increased with increasing PFO size. ...
... 23 However, the association between PFO and DCI and whether PFO closure reduces the risk of DCI remains controversial. 23 In an important study of experienced divers (N=230) by Torti and colleagues, 24 the risk of significant DCI was 4.8-fold to 12.9-fold higher in those with PFO detected by transoesophageal echocardiography, and risk was further increased with increasing PFO size. It is noteworthy, however, that the absolute risk of DCI was very low, at 2.5 events per 10 000 dives, a finding reproduced in other case-control studies. ...
... 32 Conservative measures to decrease risks of DCI include maximum depth 15 m dives, extended safety stops, utilising air with decreased nitrogen content and slow ascension. 23 Thus, the decision to proceed with PFO closure, in most cases, presents an opportunity for appropriate shared decision-making (SDM), which includes discussion of the current rigor and limitations of contemporary data and the individual diver's goals and risk profile. ...
Article
As the popularity of scuba diving increases internationally, physicians interacting with divers in the clinical setting must be familiar with the cardiovascular stresses and risks inherent to this activity. Scuba presents a formidable cardiovascular challenge by combining unique environmental conditions with the physiologic demands of underwater exercise. Haemodynamic stresses encountered at depth include increased hydrostatic pressure leading to central shifts in plasma volume coupled with cold water stimuli leading to simultaneous parasympathetic and sympathetic autonomic responses. Among older divers and those with underlying cardiovascular risk factors, these physiologic changes increase acute cardiac risks while diving. Additional scuba risks, as a consequence of physical gas laws, include arterial gas emboli and decompression sickness. These pathologies are particularly dangerous with altered sensorium in hostile dive conditions. When present, the appropriate management of patent foramen ovale (PFO) is uncertain, but closure of PFO may reduce the risk of paradoxical gas embolism in divers with a prior history of decompression sickness. Finally, similar to other Masters-level athletes, divers with underlying traditional cardiovascular risk should undergo complete cardiac risk stratification to determine 'fitness-to-dive'. The presence of undertreated coronary artery disease, occult cardiomyopathy, channelopathy and arrhythmias must all be investigated and appropriately treated in order to ensure diver safety. A patient-centred approach facilitating shared decision-making between divers and experienced practitioners should be utilised in the management of prospective scuba divers.
... However, evaluation should be carried out in divers with history of decompression illness (DCI) with cerebral, spinal, vestibulocochlear or cutaneous manifestations, a current or past history of migraine with aura, a history of cryptogenic stroke or atrial septal defect (ASD) in a first degree relative. Screening for PFO is also recommended for divers who suffered DCI after non-provocative dive profile and commercial divers who suffer from migraine with aura [17,20,21,22]. ...
... If a diagnosis of the RLS is made, divers are strongly advised to modify their diving behaviour and strictly observe save diving practices [17,22]. In addition, some divers may be offered percutaneous PFO closure with an occlusive device. ...
Article
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Current medical guidelines and regulations do not require routine examinations for the right-to-left shunt at divers. We present the case of a Polish Navy Dive Medical Officer (DMO) who more than 20 years ago suffered from decompression ilness - bends accompanied by cutis marmorata, numbness in one limb and mild vertigo. After treatment in decompression chamber all symptoms entirely resolved. Since then, despite of continuing diving, he experienced no decompression ilness symptoms. Twenty years later, then 52 years-old, the DMO was admitted as a patient to the Neurology Department at the Gdańsk Naval Hospital due to episodes of transient ischemic attacks. Contrast-enhanced transcranial Doppler ultrasound and transesophageal echocardiography were performed and he was diagnosed with severe right-to-left shunt across a patent foramen ovale (PFO). Retrospectively analyzing incident of DCI he suffered 20 years earlier, we suppose that it may have been caused by paradoxical air embolism associated with the RLS across the PFO, which was not diagnosed at the time of this incident yet. We conclude that although the risk of severe neurological, cutaneous or vestibular forms of DCI is very low, in order to increase diving safety, it seems to be reasonable to develop standards for initial PFO screening in certain groups of divers - professional divers, military divers and medical diving personnel. Contrast-enhanced transcranial Doppler ultrasound seems to be useful in RLS screening in divers. Using multi-compartment chambers equipped with an entry lock should be preferred for safe recompression treatment of divers.
... 27 PFO has been associated with multiple pathologies: migraine, platypnea-orthodeoxia syndrome, high altitude decompression sickness and, most commonly, cryptogenic stroke. [28][29][30] The association between cryptogenic stroke and PFO was first credited to pathologist Julius Cohnheim in 1877. However, modern interest began after Lechat et al. observed in 1988 that PFO was present in 40% of individuals with cryptogenic stroke compared to only 10% in controls. ...
... 27 PFO has been associated with multiple pathologies: migraine, platypnea-orthodeoxia syndrome, high altitude decompression sickness and, most commonly, cryptogenic stroke. [28][29][30] The association between cryptogenic stroke and PFO was first credited to pathologist Julius Cohnheim in 1877. However, modern interest began after Lechat et al. observed in 1988 that PFO was present in 40% of individuals with cryptogenic stroke compared to only 10% in controls. ...
Article
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Resumo A comunicação do septo atrial (CIA) representa, aproximadamente, de 6%-10% dos defeitos cardíacos congênitos, com incidência de 1 em 1.500 nascidos vivos.¹ Forame oval patente (FOP) é mais comum e está presente em mais de 20%-25% dos adultos.² Síndromes clínicas associadas a CIA e FOP são variáveis, com implicações abrangendo a medicina pediátrica e adulta, neurologia e cirurgia. O interesse adicional na anatomia do septo interatrial (SIA) aumentou substancialmente nas últimas duas décadas, com evolução simultânea dos procedimentos percutâneos envolvendo cardiopatia estrutural do lado esquerdo e procedimentos eletrofisiológicos. Idealmente, essas intervenções baseadas em cateter requerem rota direta para o átrio esquerdo (AE) através do SIA, necessitando completo entendimento de sua anatomia. Atualmente, tecnologias de imagem sofisticadas e não invasivas como ecocardiografia transesofágica bidimensional (ETE 2D) e tridimensional (ETE 3D), ressonância cardíaca (RMC) e tomografia computadorizada (TC) passaram por um extraordinário desenvolvimento tecnológico, fornecendo detalhes anatômicos das estruturas cardíacas visualizadas em formato 2D e 3D e são essenciais para diagnóstico e tratamento de pacientes com doenças cardíacas. A avaliação da anatomia e anormalidades do SIA, portanto, requer abordagem padronizada e sistemática, integrando modalidades diagnósticas e fornecendo avaliação adequada e uniforme para terapias cirúrgicas e transcateter.
... Blood shunting from the venous right atrial side of the heart to the arterial left atrial side is known as right-to-left shunt, can also cause AGE, such as a patent foramen ovale (PFO), which is a path for bubbles to avoid the washout process by lungs and enter the arterial system. This can lead to a paradoxical embolism [15]. ...
Article
The motivation of this research is to study the effect of suction process on a growing gas bubble and concentration distribution around this bubble in tissues of divers who surface too quickly. The effect of bubble motion is also considered. The method of combined variables is used to solve the problem by combining the radial and time variables into one variable by using a suitable similarity transformation that enables to divide the diffusion equation into two ODEs, the first concerns to concentration distribution and the other concerns to the bubble radius evolution. The resultant formulae are valid for both growth stages whenever the ambient pressure is variable at ascending of the diver, or constant as the diving stops or at sea-level. The effects of physical parameters are discussed when applying suction process and show that the dominant parameter is the initial void fraction. The research findings reveal the role of suction process to activate the systemic blood circulation and delay the growth of gas bubbles in the tissues and reduce the incidence of decompression illness (DCI). This research also provides evidence and agrees with the previous experimental studies to support the use of suction therapy to reduce the DCI harmful effects.
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Biofouling is called “lessons from nature”. Currently, governments and industry spend more than 5.7 billion USD annually to control unwanted marine biofouling, aquatic flora and fauna on submerged construction leading to various technical, economical, and ecological problems. In turn, the Baltic Sea is defined as a “time machine” for the future coastal ocean, as processes occurring in the Baltic Sea are related to future changes. Our study describes the biofouling community at 12 sites located at different depths on the legs of the “Baltic Beta” oil platform that resulted in finding a maximum of 1,300 individuals on 400 cm2. We analyzed: spatial distribution of dominant marine organisms living on a steel platform surface, their abundance and mass. Our work showed no significant difference in the benthic samples mass among different depths or cardinal directions of the rig columns. Our research can help to predict offshore biofouling on other devices in the Baltic Sea, to control invasive species and to estimate environmental load.
Article
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The foramen ovale is an essential component of the fetal circulation contributing to oxygenation and carbon dioxide elimination that remains patent under certain circumstances in ∼30% of the healthy adult population, without major negative sequelae in most. Adults with a patent foramen ovale (PFO) have a greater tendency to develop symptoms of acute mountain sickness and high‐altitude pulmonary oedema upon ascent to high altitude, and PFO presence is associated with worse cardiopulmonary function in chronic mountain sickness. This increase in altitude illness prevalence may be related to dysregulated cerebral blood flow associated with altered respiratory chemoreflex sensitivity; however, the mechanisms remain to be elucidated. Interestingly, men with a PFO appear to have a shift in thermoregulatory control to higher internal temperatures, both at rest and during exercise, and they have blunted thermal hyperpnoea. The teleological ‘reason’ for this thermoregulatory shift is unclear, but the shift of ∼0.5°C in core body temperature does not appear to be sufficient to have any significant negative consequences in terms of risk of heat illness. Further work in this area is needed, particularly in women, to evaluate mechanisms of heat storage and dissipation in these individuals compared to people without a PFO. Consequences of a PFO in SCUBA divers include a greater incidence of unprovoked decompression sickness, but whether PFO is beneficial or detrimental to breath hold diving remains unexplored. Whether PFO presence will explain interindividual variability in responses to, and consequences from, other environmental stressors such as spaceflight remain entirely unknown. image
Chapter
In addition to commercial specialists, diving is an easily accessible recreational activity which increasing numbers of people are participating in each year. While most participants will not have problems, patients who present with trauma having been involved in a diving incident or with complications secondary to the physiological changes experienced during diving have specific management challenges. This chapter looks at the normal physiological changes that divers experience, how these can cause problems, how to approach a diver suffering from trauma and diving-specific emergencies such as decompression illness and air emboli.
Article
Decompression illness is caused by intravascular or extravascular bubbles that are formed as a result of reduction in environmental pressure (decompression). The term covers both arterial gas embolism, in which alveolar gas or venous gas emboli (via cardiac shunts or via pulmonary vessels) are introduced into the arterial circulation, and decompression sickness, which is caused by in-situ bubble formation from dissolved inert gas. Both syndromes can occur in divers, compressed air workers, aviators, and astronauts, but arterial gas embolism also arises from iatrogenic causes unrelated to decompression. Risk of decompression illness is affected by immersion, exercise, and heat or cold. Manifestations range from itching and minor pain to neurological symptoms, cardiac collapse, and death. First-aid treatment is 100% oxygen and definitive treatment is recompression to increased pressure, breathing 100% oxygen. Adjunctive treatment, including fluid administration and prophylaxis against venous thromboembolism in paralysed patients, is also recommended. Treatment is, in most cases, effective although residual deficits can remain in serious cases, even after several recompressions.
Article
30 patients with a history of decompression sickness were examined for the presence of patent foramen ovale by bubble contrast, two-dimensional echocardiography and colour flow doppler imaging. With bubble contrast, 11 (37%) of the patients had right-to-left shunting through a patent foramen ovale during spontaneous breathing. 61% of a subset of 18 patients with serious signs and symptoms had shunting. This number was significantly higher than the 5% prevalence seen with the same diagnostic technique in 176 healthy volunteers. The presence of patent foramen ovale seems to be a risk factor for the development of decompression sickness in divers.
Article
The prevalence of right-to-left interatrial shunts was determined by contrast echocardiography in a blind comparison of 61 divers who had had decompression sickness, divided into four predetermined clinical subgroups, and a control group of 63 who had not. The prevalence of shunt was 15/63 in the controls and did not differ significantly in 24 divers with onset of neurological symptoms more than 30 minutes after surfacing (4/24) or 6 with joint pain only (1/6). In divers who had neurological symptoms within 30 minutes of surfacing the prevalence of shunt was 19/29, significantly higher. Rashes soon after surfacing were related to shunts but late rashes were not.