Hello Kev,
Can I be clear there is little room for hard dogma from anyone (including me) in relation to most aspects of this issue. So, I don't pretend to have definitive evidence based answers. However, I would make a couple of comments about that video.
First, it is most unlikely to be as easy to replace a regulator in a seizing diver as portrayed. Most people suffering seizures clamp their mouths shut and messing around trying to get the mouth open and then accurately place a regulator is likely to waste valuable time and risks flooding the airway with water. What is most likely to keep the airway dry is to establish an ascent, and the expanding gas passing out of the airway will help prevent water passing in. It is remarkable how often we have seen unconscious divers brought to the surface quickly with little or no water contamination of the lungs.
Second, I can understand the logic behind continuous gentle purging of the regulator, but this is a potentially dangerous intervention. The difficulty is in knowing what gentle purging means and accurately maintaining it. If you overdo it there is a danger of increasing the risk of pulmonary barotrauma during the ascent. There was an Australian military case in which this occurred. With substantial regulator purge from moderate depth (I can't remember exactly - around 40m I think) there was gross introduction of air into the circulation and the diver died. Moreover, it contributes to task loading of the rescuer and if you get on with the ascent, it should not be necessary in preventing water entry to the airway for the reason I describe above.
Third, while I get that the video adheres to the UTD philosophy of trying to make everything look as relaxed as possible, the ascent is too unhurried and slow. If I was not overly concerned with my own decompression obligation I would have just grabbed the diver, put their head in a neutral position, and swum quickly to the surface. There is little doubt that this is what would be best for the unconscious diver. In the scenario depicted (a diver with reg in place, clearly breathing) the slow approach taken looks OK and maybe could work, but rescues are not usually like that. Also, the notion that an airway can be managed and well protected from water entry in a breathing but unconscious diver over the course of a nice relaxed ascent while the rescuer also adjusts multiple buoyancy controls is tenuous at best. There is a good chance that a rescuer would drown a diver in trying to do it. Nevertheless, I refer back to my comment about dogma above, and have to admit that I cannot definitively claim it can't be done.
Simon M
