Should PFO Screening be made necessary for Tech diving

[Divejones]

after having read through 143 threads on PFO and references to PFO, this thing still irks me. Should a PFO screening be made mandatory for tech diving or even scuba diving. so that one is free of DCS worries. With Cost vs Benefit analysis, is it worth it ? I am drawing a parallel with screening for a Fighter Pilot, where screening takes place, both for psychomotor skills and medical screening (Incl PFO)


PS
For starters

Patent Foramen Ovale

PPS
Views from Doug and DDM solicted

 

[Dr Deco]

Dear Divejones:

Relationships between a PFO and serious DCS are not strong. Screening has not been recomended over the years. In addition, the test procedure is not without risks [surprisingly].

 

[Divejones]

..the test procedure is not without risks [surprisingly].

any links sir, would help.

 

[Dr Deco]

Hello Divejones:


As oftenhappens, when you search for something on Pub Med, it does not appear. As I recall, however, a PFO test for an individualwith symptoms, e.g., a diver with repeated CNS DCS is warranted since the riskis small. However, random testing on ageneral diver population is not considered prudent.

A sizable portion of the population [25%], including SCUBA divers, has a PFO and they donot encounter DCS with any higher frequency. This has been checked by retrospective tests of divers following a DCS incident. Repetitive DCS is a different story, but normal, incident-free diving is considered to be no cause for a PFO test.

Sorry I am lacking any references.

Dr Deco :doctor:

 

[AFdivedoc]

Divejones,

after having read through 143 threads on PFO and references to PFO, this thing still irks me. Should a PFO screening be made mandatory for tech diving or even scuba diving. so that one is free of DCS worries. With Cost vs Benefit analysis, is it worth it ? I am drawing a parallel with screening for a Fighter Pilot, where screening takes place, both for psychomotor skills and medical screening (Incl PFO)

A negative screening for PFO (via the "bubble test") does not make one "free of DCS worries". The PFO test only checks for a potential right to left shunt in one anatomical area. There are other structural anomalies that can provide a right to left shunt, including pulmonary vascular bed abnormalities and arteriovenous malformations (AVMs) in other areas. As Dr. Deco said, the relationship between simply having a demonstrable PFO and clinical DCS is not a strong one. Checking for PFO after a repetitive neuro hit or an "undeserved" neuro hit yields more in that if it is positive, you have a diagnosis and the location of the shunt. A negative test after the aforementioned hits may mean there is no shunt, or that it exists elsewhere.

We do not routinely screen fighter pilots for PFO in the US. In fact, I've done many, many initial flying physicals for the USAF, and I've never referred anyone for a bubble test to screen for PFO. For an otherwise healthy young applicant with no history and a normal exam (no murmurs, etc), routine ECG is all they get in addition to comprehensive vision and hearing testing and various blood and urine studies. Other screening or specialty referral is driven by abnormalities found on history and physical exam. I'm not saying this is the best process or or better than any other military service's program, but it works for us. We have a lot of pilots and a lot of applicants.

Additionally, the US Navy does not routinely screen their dive candidates for PFO.

An effective mass screening test is sensitive and specific for the condition, low risk, and easy and inexpensive to administer. PFO screening via the saline bubble test does not meet all these criteria.

Cheers,
AFdivedoc

 

[Divejones]

Thank you Dr Deco and AFdivedoc, couldn't have been put more eloquently. my son (12) daughter (10) want to take a plunge, i have seen some nasty DCS in air and after diving (including death due explosive decompression, when a colleague lost his canopy), that's why the worry on PVO, i heard 1 in 4-5 have this shunt open or potential for it to open under certain conditions and direct correlation to DCS dived under existing dive table doesn't exist. so going ahead with them getting under water.

Thank you all again

 

[Duke Dive Medicine]

Hi Divejones, sorry I was out the week you posted this and just saw your request today. I don't have much to add to what Dr. Powell and AFdivedoc said, other than to say that we do not endorse routine screening for PFO either. As was pointed out, anywhere from 20-30% of the population has a PFO, but the rate of decompression sickness is significantly less than that. What I call the irony of PFO is that we only screen for it after a diver suffers a DCS hit that makes us suspect it. Even then, if the diver does have a PFO, there's no conclusive proof that the PFO was a factor in his/her decompression sickness.

Best regards,
DDM

 

[DocVikingo]

Hi Davejones,

You may find the following article informative --> Alert Diver | PFO and Decompression Illness in Recreational Divers

DAN is currently in the data collection phase of a study of this issue in technical divers.

Regards,

DocVikingo

 

[DocVikingo]

any links sir, would help.

Hi Davidjones,

There really are no risks associated with transthoracic echocardiography (TTE).

With transesophageal echocardiography (TEE), risks are very low in healthy individuals but include adverse reactions to the numbing agent used on the throat, breathing problems, heart rhythm issues, infection of heart valves & bleeding of the esophagus.

Regards,

DocVikingo

 

[Dr. Doug Ebersole]

I have been off the boards for several days -- diving -- so I missed this thread and want to thank HowardE for directing me to it.

I really have nothing to add beyond what has been said. PFO is very common in the general population (approx 25%) and you would expect a similar incidence in the diving community. The risk of DCS is probably 5 fold higher in those with PFO than in those without (Data from Dr. Alfred Bove, MD) but the absolute incidence is still very low. For recreational divers, the incidence of DCS is somewhere around 2 per 10,000 dives so a 5-fold higher incidence would only be a risk of 1 DCS event per 1000 dives. The risk of DCS is obviously somewhat higher in technical diving because of the higher bubble load but it would still be very hard to ever justifiy the expense of screening all technical divers for PFO.

Additionally, as mentioned above just because someone has a PFO and has DCS that doesn't mean the two are related. Currently, I feel it is "reasonable" to close a PFO in someone who has had multiple unexpected neurologic DCI events, but this is only my opinion. There are other cardiologists who do not share my opinion and would not recommend closure for any divers. That is why we need more information and less opinion. Along those lines, DAN is sponsoring a 5 year study of divers with PFO and DCI. I am the principal investigator of the study and would like to take this opportunity to again look for potential subjects for the study. Please contact me if you or any of your friends/buddies/colleagues would be interested in learning more about the study.

By the way, I practice what I preach. I am a CCR trimix instructor who routinely dives well beyond recreational limits. I also do TEEs and close PFOs as part of my job. However, I've never been tested for one as I've (fortunately) never had a DCS event. Food for thought.

Doug