So after reading this whole string of postings, here is my question:
What has the gear got to do with this injury?
This is a lung expansion injury caused by not exhaling while ascending. A lung expansion injury is just as lethal with a regulator in your mouth, as without. All of the rest is simply fluff. Ascents with a breath coming from compressed air (from a submarine, a diving bell or a scuba tank) all require an open air way when surfacing.
Agreed, it is a lung expansion injury. I'll try to clarify my point as it relates to gear.
The point I was trying to make is information overload. If you try to load a student up with too much information and they can't assimilate it all, they'll forget something. I can't tell you how many times my open water students need to be reminded to exhale (when the reg isn't in their mouth) during the class, even on the most basic of skills/exercises. We are throwing so many things at them that they need to remember, sometimes they simply forget. In that sense, the complexity of the skill, as taught, requires many components and the student has to remember a lot of things in sequence to perform the skill adequately. As such, they can easily be overwhelmed / overloaded and forget something. The lack of any way to breathe on the way to the surface, should something go wrong, can contribute to increased stress and if they are already overloaded, they can more easily forget to exhale on the ascent...they simply don't think about it...all they care about is getting to the surface. By keeping the regulator / gear intact on the ascent, that stress is removed.