PFO Testing

[pbnorris]

Dear Dr Deco:

What is your opinion about being tested for PFO before engaging in diving that required extensive staged decompression?

There are (non medical) individuals who have extensive practical experience who present some compelling arguments in favor. I'm sure it wouldn't hurt to be tested, but are clinical tests accurate enough to place confidence in them?

If an individual wished to be tested, could you recommend a place to start finding a Physician who was versed in diving physiology, or would a just about any Cardiologist be able to administer the test?

Thank you.

 

[Dr Deco]

Dear pbnorris:

Readers have inquired about this PFO testing before and to my knowledge there is still not a good answer for this.

The arguments are not extremely compelling for getting DCS with or without a PFO UNLESS the type of diving may be provocative enough to produce many decompression gas bubbles. These could of course then arterialize through the PFO and go to the brain (or spinal cord).

According to my readings of the medical literature, the best tests are those using either a transesophageal ultrasound probe or a transcranial Doppler (TCD) approach and saline echocontrast. The latter is more convenient and appears to be as sensitive as the former. The contrast common echocardiogram is not very sensitive. At NASA, we used the TCD method. One must also look for the shunt volume that is identified by the number of bubbles in the middle cerebral artery if a PFO is present. This also tells you if you have a “resting” PFO or an “augmented” PFO.

I am not aware of individuals performing this TCD test in the United States although it is not difficult. This is somewhat complicated business, and it is not clear form the diving records that testing is very necessary. The situation is different in divers who have sustained CNS DCS in the past and wish to continue diving because they are commercial workers. In Europe, an Amplatzer device has been implanted to close the hole. This can be performed without surgery through an arm vein. The device is not yet approved for use in the US.

This is my understanding of the PFO situation as we use it in a research setting. Some of the physicians in the FORUMs may have some other thoughts for you.

Dr Deco

 

[ayesa]

Dr. Deco:
I've just started my OWC, so I'll like to know what is PFO?

 

[Dr Deco]

Dear ayesa :

The reference to a PFO was to a patent foramen ovale. This is an opening in the heart that is present when is developing baby in the mother’s uterus. The blood shunts past the inactive lungs through this opening. When one is born and takes the first breath, this opening begins to close and by one year, it has sealed in ¾ of the people.

The question remains as to whether it causes a problem for the ¼ of individuals who may be divers. Does this opening allow decompression gas bubbles to pass from the veins into the arterial circulation and then embolize the brain?

Dr Deco

 

[ayesa]

Thank You.

 

[pbnorris]

Thank you for your reply.