freediving after SCUBA

[Dr Deco]

Hello phishphood:

Arterialization

This was an early question on the Ask Dr Deco forms back in 2000 and 20001. Arterialization of bubbles is a possibility. I tested this in the laboratory with sheep and found no arterialization whatsoever. However, sheep are quadrupeds and are standing when dived in a hyperbaric chamber. Humans dive head down when descending and this changes the hemodynamics [blood flow] of the system. Arterialization could well be promoted in such a case.

Bubble Formation

As answered a decade ago [two are listed in the posters references], surface swims post dive [e.g., less than an hour] can cause bubble formation/enlargement by pressure reduction in small volumes of tissue. The tissue is loaded with nitrogen from the scuba dive and then the diver kicks around on the surface. Strenuous musculoskeletal activity is known from laboratory studies to promote bubble formation.

Dr Deco

[dumpsterDiver]

Thank you everyone for the info. I figured as much, but couldn't quite get it figured out in my head. I suppose I'll do my best to not go more than 5' under during my 'surface' intervals and hope for the best. On that note, would it be best just to treat freediving as flying and wait 24hr give or take after the last tank dive to completely off-gas?

James- I'm glad you understand my, er... pain at this decision and the self-restraint it calls for.

And for everyone: apologies I had to post this when there obviously have been multiple posts about it in the past. I can't find them when searching, but the forum "similar threads" tool pops up a ton of them

Freediving after scuba is dangerous. I wouldn't worry about a 5 or 10 or 15 foot freedive if you come up real slow and you wait a couple hours after a scuba dive and you just do a few drops. I used to take 2 tanks out in a raft, scuba dive in 20 feet for around 3 hours and then immediately freedive hard for another couple hours in the same depth and never had any problem.

It would be safer to wait 24 hours, but I have waited around 12 hours after scuba diving hard to 120 feet on several dives and then first thing in the morning doing some freediving to 60-70 feet.

From everything we know, you should freedive before scuba diving.