Exertions following diving

[bygolly]

I understand that part of the screening test for PFO involves the use of a Valsalva maneuver to increase intra-thoracic pressure which may open an unsealed PFO and allow right to left shunt of the injected micro-bubbles. Exertions following a dive such as climbing a boat ladder fully kitted or moving heavy gear about on the deck could produce the same increase in intra-thoracic pressure and shunting. I have seen some discussion on the boards regarding exertions immediately following a dive and the advice to avoid such things but I have not heard anything lately.

Are these precautions still valid?

If so should boat operators be re-considering how they board divers after a dive...especially provocative dives?

Do you know of any studies that have included this factor or any studies that plan to?

Cheers and thanks in advance.

 

[DocVikingo]

Hi bygolly,

It is wise to avoid exertions such as you describe for a number of reasons, chief among them:

1. Concern that rapid or powerful movements of adjoining bodily surfaces such as joint, other skeletal and muscle surfaces, through the processs of cavitation/tribonucleation, may produce microbubbles that could serve as seeds for larger, potentially DCI-causing bubbles.

2. Concern that divers with a PFO will force the venous bubbles that are common following diving into arterial circulation.

Regards,

DocVikingo

This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual, and should not be construed as such.

 

[Dr Deco]

Hello bygolly:

Straining and the PFO Problem

Your question concerning the Valsalva maneuver bubble passage through a PFO is a good one. Over the past decade or so, several writers [me included] have written about this. The strain-and-release associated with breath holding and the passage of bubbles through a PFO still stands as a problem.

Valsalva Maneuver

This maneuver results in an increase of intrathoracic pressure in the chest, then a release of this pressure and the rapid influx of blood into the heart. This happening, the pressure in the right side of the heart increases and temporally allows a right-to-left pressure gradient in the heart. This is opposite to the normal L-R pressure gradient. Bubbles can thus pass into the arterial side of the circulatory system.

Researchers have investigated this with respect to blood clots and stroke. They find that other actions can also effect the gradient reversal. These are simple things such as coughing and sneezing. Studies have found that straining maneuvers such as moving furniture, strenuous defecation,pumping bicycle tires, and pulling up weeds are provocative actions. Therefore, climbing up a boat ladder certainly qualifies as a trouble maker for the diver. We all know that people hold their breath for a short time as they exert themselves. Whether or not you call it a Valsalva maneuver, it still is.

"What's in a name? That which we call a rose
By any other name would smell as sweet."
- Shakespeare,Romeo and Juliet (II, ii, 1-2)

Post-dive Activity

I believe that I was the first to suggest that activities such as climbing a boat ladder with your tanks and weights are very bad ideas with respect to the PFO/bubble question. Remove the equipment and pass it up to someone on the boat. I have called this assistance “valet diving.” Others have suggested that one wait for several minutes at the surface before reboarding [the “hidden stop”], especially if the dive has been provocative. These might occur with a long dive or especially one where the diver was swimming against a current.

Also,moving tanks and such are very provocative. It seems also that body position [sitting or recumbent] plays a role in arterialization.

I do not know that more studies are planned by the diving community [money problems]. Most work has been done by the medical community with respect to stroke, especially “paradoxical stroke.” [This latter means the clots do not originate in the left heart or the carotid artery but rather the venous side.]

Dr Deco :doctor:


References

Balestra C; Germonpre P; Marroni A (1998). Intrathoracic pressure changes after Valsalva strain and other maneuvers: implications for divers with patent foramen ovale. Undersea Hyperb Med; 25(3):171-4

Stoddard MF, Keedy DL, Dawkins PR. The cough test is superior to the Valsalva maneuver in the delineation of right-to-left shunting through a patent foramenovale during contrast transesophageal echocardiography. Am Heart J. 1993Jan;125(1):185-9.

Lao AY,Sharma VK, Tsivgoulis G, Malkoff MD, Alexandrov AV, Frey JL. Effect of body positioning during transcranial Doppler detection of right-to-left shunts. EurJ Neurol. 2007 Sep;14(9):1035-9.

Powell, M.R., K. V. Kumar, W. Norfleet, and J. Waligora, B. Butler (1995). Patent foramen ovale and hypobaric decompression. Aviat Space Environ Med. 66(3):273-5

Schwarze JJ, Sander D, Kukla C, Wittich I,Babikian VL, Klingelhöfer J. Methodological parameters influence the detectionof right-to-left shunts by contrast transcranial Doppler ultrasonography.Stroke. 1999 Jun;30(6):1234-9.

 

[bygolly]

Thank you both!