Disorientation and uncontrolled ascent on night dive

[Iralub]

Some random thoughts...

If you have what is normally considered a pretty good breathing rate for an experienced diver, and if you were at about 15 meters for 45 minutes, then you would have used nearly 60 cubic feet of nitrox, which is about 3/4 of the common aluminum tank. You said you had half your tank left, so maybe you were using a larger tank. Whatever size tank you used, you had gone through maybe as much as 5 pounds of gas at that point, so you were that much more buoyant.

Boulderjohn, once I got my computer data into Subsurface and entered the start and end pressure, it calculated by SAC rate for me. For this series of dives (22 in all), with the AL63 tank, it is showing that my average SAC was 9.7L/min, with a range between 8.3L/min and 11.3L/min (the latter being on a dive where I got quite exhausted in surge/current and noted poor air use in my log).

From a previous dive trip, it looks like my air use is worse on an AL80 tank, even in thinner suit and less weight (average 10.8L/min).

No idea whether that's considered a good breathing rate for experienced diver (I'm not very experienced), but having 100 bar at the end of that dive is consistent SAC for this range. It would still mean I will have used over half my air and could have contributed to the buoyancy issue.

Thanks so much for your excellent advice on this issue.