Kharon
Contributor
Spontaneous Pneumothorax is an absolute contraindication for SCUBA diving.
Not true. I had 3 events in 1967. After the third the doc scarred the pleurum with talc. Since then I've had no more events and have been medically cleared for diving. Treatment and time without recurrence isn't a perfect indicator but I'm more than willing to take the minimal risk for the huge reward. The OP has had 15 years event free.
Now, let's look at the OP's question somewhat scientifically. A spontaneous pneumothorax can be an almost instantenous event (worst case) so let's go with that. If both lungs pop at the same time you're dead meat unless you are on the table in an emergency room at the time. So let's say only one goes. At 15 feet that's +½ ATM. So on ascent the air in the chest cavity would expand to 150% on one side and be distributed through the cavity semi-equally - about 125%, more or less. Painful? Almost certainly. Dangerous? Almost probably. Survivable? I would guess, Almost surely.
I think the OP should consult with a good lung guy (doesn't need to be a diving doctor) that can give an accurate probability of recurrance. Diving has nothing to do with it unless you are ascending while holding your breath. That would put you at (probably) higher risk than average. There is no increased pressure on the lungs at any depth unless you ascend while holding your breath.