What's the shallowest anyone's ever been bent?

[Lynx737]

The subject is never going to be meaningful as someone who does pick up a shallow bend when totally unexpected may have a PFO where a percentage of the absorbed nitrogen bypasses the lungs and as a consequence the diver has more nitrogen in their system than an equivalent diver on the same profile but without a PFO.

I don't have a PFO but if I knew anyone who did get bent from a shallow depth I would suggest the get their heart checked before diving again.

[nigelH]

Originally Posted by Lynx737

The subject is never going to be meaningful as someone who does pick up a shallow bend when totally unexpected may have a PFO where a percentage of the absorbed nitrogen bypasses the lungs and as a consequence the diver has more nitrogen in their system than an equivalent diver on the same profile but without a PFO.

I don't have a PFO but if I knew anyone who did get bent from a shallow depth I would suggest the get their heart checked before diving again.

This doesn't make sense to me. On a shallow dive you never exceed the ppN2 you are exposed to. If that if insufficient to produce bubbles there is no bend.

Anyway the people who know seem to rate the problem with a PFO is that it shunts bubbles, it doesn't bypass sufficient volume to affect the arterial N2 tension. However there have to be bubbles before a PFO can shunt them.

I am very sceptical about reports on shallow 'bends'. I suspect many of them were other problems and they resolved in the pot so they got put down as a bend. Most of my aches and pains go away in an hour or so so I ignore them, I would be more suspicious if I'd just been diving, but to date nothing.

[Lynx737]

In the hope of improving my knowledge I am confused by the comments about PFO's shunting bubbles. I understood that as blood leaves the venus system from the heart to the lungs nitrogen would cross due to a higher tension in the blood than in the lungs (assuming off gassing) and be exhaled. With a PFO some venal blood would cross back into the aterial system missing the lungs and therefore missing the opportunity to off gas. When the diver exits the water there exists a greater probability of bubble formation due to the increased Nitrogen that bypassed the lungs.

I agree that getting bent from very (<6m) shallow dives is difficult as the nitrogen saturation levels are unlikely to exceed the tension difference required to form bubbles. However we are all different and so many other factors have an effect and what seems impossible is always possible.

L