[immerlustig]

here is my opinion on that:

in case you don't feel like reading the whole post scroll down to where it says 'conclusion'.


- How likely it is that a BO'ed person will get water in the lungs (even after exhaling air but as long as the diver is on the way up)?

one thing that can happen underwater is a laryngospams which can be triggered by water entering the airways (accidentally sucking in water) or by panicking. i am not aware of any studies which say a laryngospasm will happen every time a diver bo's under water. therefore there is a possibility that the diver gets water into his lungs. also, the laryngospasm will release after some time with the same result (drowning/secondary drowning).


- How likely it is that if such a thing happens the safety diver will grab the blackoutee before then? (some show distress signals, some don't so I'm asking about how long after a BO it is likely to happen)

not sure what you mean here. usually there are quite a few signs of an impending bo. realising these is crucial in order to react quickly. for example: slowed or accelerated kicking, uneven kicking rhythm, seemingly tense body, looking to surface, facial expression, uncontrolled exhalation, etc. ideally the spotter knows the divers usual behaviour/style on ascent which makes it easier to detect anything "wrong".


- How likely it is that this kind of mouth-block would actually work preventing that?

the mouthblock is in our experience the easiest and most efficient way of getting a diver to the surface for a few reasons:
1. it is easy to grab the diver from any angle
2. the spotter does not have to turn the diver around to get into a position to the side or behind the bo’d diver
3. the mouthblock is very easy to apply and properly seals off the airways under water.
4. works easily with/without mask/noseclip
5. reduces chances of water in the mouth/throat which will lead to major problems on the surface


- Do you think sealing the diver's mouth while going up takes more time than just getting the diver to the surface? (more encumbered swimming, getting in the right position/grab) How much more? Has this been tested by anyone?

timewise i find the mouthblock faster or at least as fast as any other method i have tried. and yes, it is being tested/practised regularly. for the rest see above.


- Since the mouth-block is actually a jaw block, is there any risk to the neck? how about tongue?
we do not apply the 'jaw-block'. the divers head is effectively 'clamped' with one hand on the back of the head and the other hand in the face (covering the mouth). there is no strain on the neck since the diver is neutral or positively buoyant anyway.


conclusion:

it seems to me that the 'mouth-block' ascent is the easiest, safest and most efficient method (i am aware of) for rescuing a bo'd diver underwater. the biggest advantage over other methods is the fact that, if done properly and quickly, there will be no water in the victims mouth and throat. if that would be the case there is no way to effectively remove that water from the divers mouth (since you are floating on the surface) to allow spontaneous breathing. water in the mouth can delay recovery and delay the release of a possible laryngospasm. i feel that the first actions of the safety diver are decisive in the outcome of a bo. any possible complications, however rare they are, will lead to major (!) problems which only very, very few people are actually trained to handle. so practising rescues regularly is important.

just my 2 cents,

roland

p.s. if someone could send me a pm how to insert quotes in a post i'd very much appreciate it :-)