juggernutt:
http://www.scubaboard.com/t54396.html
This is the incident that happened to me...after ascending from 20 meters depth.
I dove down again for a few minutes...
According to a friend..this was a definite NO-NO.
The DM shouldn't have taken me down under again. I risked a lungemboly(air in my lung?!?) and might even have damaged it.
Is this true?
It sounds from your description like you had an over expansion injury, (mediastinal emphysema) an over inflation of the lungs resulting in alveolar rupture with an escape of air into the area of the chest under the breastbone.
If no other symptoms presented then you may have gotten lucky, no AGE or air into the circulatory system
In either case you should not have been brought back to depth in that situation, one reason is when symptoms of any pulmonary over inflation syndrome are present you should have been given a neurological examination to rule out AGE.
Another reason equally important is during your rapid ascent and time on the surface nitrogen began to off-gas in your tissues, going back to depth does shrink these bubbles but once formed they do not re-dissolve or disappear when you return to depth. In some cases these micro bubbles can bypass the pulmonary circuit and get into arterial circulation, here the damage they can cause is much more immediate and severe than a venous bubble
This is why you should not free-dive or breath hold dive after making a SCUBA dive.
And lastly as your friend mentioned to you it is possible the over inflation resulted in a pnuemothorax (the escaped air becomes trapped between the membranes lining the lung and the inner chest wall) in this case if gas continues to escape at depth the resulting expansion on ascent would most likely be fatal (a simple application of Boyles law)
The risk of AGE (an escape of gas from alveolar rupture
Glad your OK, but these are items all divers need to be familiar with. Barotrauma and POIS can occur with depths as shallow as 4 FSW and are of much more concern to most divers than DCS will ever be...
Jeff Lane
