Mouthpiece Retaining Head-strap

[gianaameri]

Hi All

This post has now had over 8000 viewings and so appears to have raised quite a lot of interest amongst a membership of just over a 1000. However despite the interest shown, because the topic is a rebreather safety crusade of mine, I'd like to re-energise the thread.

By now most of you will have read Mike's courageous post about his hypoxic loop experience on the lessons learnt forum. Ceasing to exist is just one mistake away for all of us who enter an alien environment. I make no judgement on Mike other than to thank him for having the courage and integrity to share the experience with us so we can all learn from it. I'm sure the vast majority of the membership share the sentiment.

I believe the general scenario Mike found himself in, common to a number of rebreather incidents, some unfortunately fatal, is a great example of where a mouth piece retaining strap can make the difference between surviving an incident or not. Whilst swimming at the surface, Mike was sufficiently self aware of something not being right to look at his hand display; PO2 0.1 bar! Unconsciousness was likely seconds away. Good fortune was on Mike's side that day, a likely and alternative physiological hypoxic response might have been a feeling of well being as he peacefully slipped into unconsciousness oblivious to his PO2.

Bearing in mind you can drown / asphyxiate face down in a puddle, let us then consider a diver in this situation and assume Loss Of Consciousness (LOC) and the diver is positively buoyant. A mouthpiece retaining strap, if worn correctly, will prevent that mouthpiece from being dropped. As a consequence the airway and breathing loop are wholly or partially protected from flooding, likely providing sufficient time for the diver's situation to be comprehended by those around and an effective rescue implemented (this could be many minutes if swept away in the tide from a buddy / safety boat). If the diver was negatively buoyant he/she would cease to fin and as a result begin to sink. The PO2 would quickly rise to the point where consciousness would be regained. Because the diver has not inhaled water and because the breathing loop has not flooded, the diver is now potentially given a second chance of life through the implementation of self rescue or a buddy has been given time to initiate an effective response. The probability of a positive outcome has now been increased.

Lets now look at the alternative and let us assume no mouthpiece retaining strap is used, the very likely scenario now is the mouthpiece is dropped as the diver relaxes into unconsciousness. If face down, the next inhalation will be water and asphyxiation will quickly ensue. Even if positively buoyant, face down in the water for a few minutes will most likely result in death or brain injury. If the diver is already negatively buoyant, the situation is of course now much worse, the descent rate accelerates as the loop / lungs vent gas, which is replaced by water, along with of course Boyle's law acting upon every other gas space, which the unconscious diver is unable to compensate for. The diver will likely be lost and the probability of surviving this incident has now significantly diminished; all for the sake of failing to use what can be in it's simplest form, a $10 rubber mask strap.

As I keep saying, there are no guarantees here, however hypoxia is one of, if not the largest rebreather disabling injury and drowning is by far the single largest cause of death in rebreather fatalities (it's over 90% of cases according to DAN research). By putting a simple measure in place to protect both the airway and breathing loop from water ingress in the event of LOC, will significantly increase the likelihood of delaying drowning and loop flooding thus potentially providing either yourself or a buddy the opportunity or additional time to implement a rescue.

For those then who do use, or have started to use a mouth piece retaining strap, please let us know how you have got on so new members can learn from your experience. Also if you have ceased to use a mouth piece retaining strap or refuse to use one, again please let us all know why so we can discuss your reservations.

2013 - The Year Of Rebreather The Mouthpiece Retaining Strap?

Come on CCRX, together we can do it ;-)

Rgds Paul

I am not a Crusader, but I like your Crusade and its spirit.

You'll need to write to the CE Technical Committee currently revising the EN14143 standard, because if a requirement for a BOV is not included in the standard, any such addition would be forbidden.

If you wear a BOV and teach, you are breaking HSE requirements on Meg, rEVO, JJ...

Safer and yet, you can't.

Crazy huh?

 

[cardysnr]

My regular CCR buddy has now moved to a FFM with BOV....

I've Just bought a Drager strap (2nd hand Revo one) to use with my BOV.

Have to say a THANK YOU to the REVO Daddy (P.R) for potential of buying a new one direct even though I'm not a REVO diver...Top bloke :trophy:

David.

 

[JacobT]

Dang, I knew there was something missing from my Christmas wish list.. ah well will have to get one ASAFP (as soon as financially possible )

Unfortunately, the previous owner of my rEvo cut it off and threw it out :-(

 

[gianaameri]

I am not a Crusader, but I like your Crusade and its spirit.

You'll need to write to the CE Technical Committee currently revising the EN14143 standard, because if a requirement for a BOV is not included in the standard, any such addition would be forbidden.

If you wear a BOV and teach, you are breaking HSE requirements on Meg, rEVO, JJ...

Safer and yet, you can't.

Crazy huh?

When I wrote the above I was at the airport and somehow mixed retaining strap with BOV... the thoughts interlaced by instinct and not by accident.

Personally, I feel a retaining strap without a BOV has little safety value. You need both to make a difference.

To provide effective rescue, or self-rescue, in case of gas poisoning (hypoxia, hyperoxia, hypercapnia) the key thing is being able to switch to a breatheable gas (and to breathe it comfortably for a long enough period of time to clear your system).

You cannot switch to a bretheable gas unless there is a BOV which the buddy can operate in case you are unconscious or impaired (he cannot remove the mouthpiece and insert another without drowning you).

If you are about to go unconscious, you cannot self-rescue unless you can quickly operate the BOV and give yourself fresh gas (not enough time and clarity of mind to perform any complex task requiring more than maybe a second and reflex action).

I did in Mod 1 the drill where you rescue an unconscious diver still wearing a DSV by flushing his loop, but that I feel is far more difficult than switching a BOV, and far too difficult to perform for a sustained period of time in the real diving environment.

For all intensive and practical purposes, the real safety value is in the combination of BOV + Retaining Strap (and not merely a Retaining Strap on an ordinary DSV, although this is still better nothing).

 

[NSRB]

I have used the Drager mouthpiece retaining strap since day one of my Mod 1 training (that would be just before coffee break in terms of my CCR experience !).

Having said that, at first it was strange and uncomfortable however when properly adjusted (not too tight or too loose) it is very comfortable and allows you to relax your jaw making for a much more enjoyable dive. When i was first conducting bail-out drills I attempted to remove the DSV and push the loop up, this was a non-starter for me and found it much more efficient to simply remove the DSV and push it down. I will be installing a Shrimp BOV in the near future and intend to keep the retaining strap as I believe the advantages far outweigh any perceived disadvantages.

Cheers,

John

 

[WFO]

Is the revo strap mentioned earlier similar/the same as draeger style one with the "lip cushion" type arrangement around the mouthpiece?

Does this device rather than just a normal strap provide benefit and are they readily available anywhere?

 

[gianaameri]

Is the revo strap mentioned earlier similar/the same as draeger style one with the "lip cushion" type arrangement around the mouthpiece?

Does this device rather than just a normal strap provide benefit and are they readily available anywhere?

I bought mine here (quality supplier):

Dräger Mundstück mit Kopfband | Online Shop | W+S Water Safety Europe GmbH | Seit 1999

The design allows for the correct angle of pull and the correct positioning of the head strap.

The head strap must go over the crown and not the back of the head, or your mask may leak, and the Draeger design allows for this, whilst pulling at the correct angle to make it comfortable to wear at the mouth.

The additional surface area around the mouthpiece may provide a little bit more seal, but I think it is largely for support, comfort, and correct angle of pull.

I used it a lot and I like and it works.

 

[Rickoz]

Drager Mouthpiece

I bought mine here (quality supplier):
Dräger Mundstück mit Kopfband | Online Shop | W+S Water Safety Europe GmbH | Seit 1999
The design allows for the correct angle of pull and the correct positioning of the head strap.
The head strap must go over the crown and not the back of the head, or your mask may leak, and the Draeger design allows for this, whilst pulling at the correct angle to make it comfortable to wear at the mouth.
The additional surface area around the mouthpiece may provide a little bit more seal, but I think it is largely for support, comfort, and correct angle of pull. I used it a lot and I like and it works.

I have the Drager mouthpiece but have yet to use it.
If the strap of the mouthpiece is to go over your crown of your head then what is the preferred setup? Mouthpiece or Mask placed on first as one strap will overlap the other.

 

[NSRB]

I have the Drager mouthpiece but have yet to use it.
If the strap of the mouthpiece is to go over your crown of your head then what is the preferred setup? Mouthpiece or Mask placed on first as one strap will overlap the other.

I don the mouthpiece strap followed by the mask strap. I have a neo mask strap cover that allows the mask to slid easily over the mouthpiece strap. I should mention that we dive cold water here so a DS hood is always used.

 

[Rod Macdonald]

I don the mouthpiece strap followed by the mask strap. I have a neo mask strap cover that allows the mask to slid easily over the mouthpiece strap. I should mention that we dive cold water here so a DS hood is always used.

I put my mask on first - then pull my hood over my head and the strap. Then the mouthpiece retaining strap just goes over my hood and is the only thing on top of my hood. Works a treat for me.

 

[Mike Ferguson]

I have the Drager mouthpiece but have yet to use it.
If the strap of the mouthpiece is to go over your crown of your head then what is the preferred setup? Mouthpiece or Mask placed on first as one strap will overlap the other.

I put my mask on first and then the mouthpiece strap. I use the AP strap and it sits at the back of my head rather than the crown. That way you don't disturb your mask if you suddenly need to raise the mouthpiece over your head for any reason (like trying to stop it filling with water when you remove it from your mouth in a hurry without closing the DSV / BOV ...)

mike

 

[Dave Sutton]

Is the revo strap mentioned earlier similar/the same as draeger style one with the "lip cushion" type arrangement around the mouthpiece?

rEvo uses Draeger parts (Draeger Ray DSV modifiied slightly).

The mouthpiece with included strap is the Draeger one, with mouthpiece and lip-flange. This is the best for maintaining an airway when unconcious, and is nearly identical to the one fitted to the LAR-V 02 rebreather.


Dave

.

 

[gianaameri]

I have the Drager mouthpiece but have yet to use it.
If the strap of the mouthpiece is to go over your crown of your head then what is the preferred setup? Mouthpiece or Mask placed on first as one strap will overlap the other.

I wear the mask first.

Then, the hood.

Then, the helmet.

Then, the crown strap on top of the helmet and helmet lights (the Draeger crown strap is long enough).

Crown strap must be last thing of course, otherwise you cannot slide it off to remove the BOV to either continue the bail-out on a standard second-stage or ditch the rebreather.

When I dive without helmet at sea in day-time, the crown strap goes on top of the hood instead (mask strap under the hood).

The key thing is that you do not want to put another strap pulling forward on top of the mask strap pulling the mask back (as you dive the two straps will interfere and the mask will leak annoyingly, especially if you use one of those neoprene back straps with nylon webbing, which is my favourite choice for mask strap).

If mask strap and crown strap are crossing each other at an angle, rather than working near parallel and on top of each other, they do not interfere with each other in any significant way.

 

[WFO]

I bought mine here (quality supplier):

Dräger Mundstück mit Kopfband | Online Shop | W+S Water Safety Europe GmbH | Seit 1999

rEvo uses Draeger parts (Draeger Ray DSV modifiied slightly).

The mouthpiece with included strap is the Draeger one, with mouthpiece and lip-flange. This is the best for maintaining an airway when unconcious, and is nearly identical to the one fitted to the LAR-V 02 rebreather.


Dave

.

Cheers chaps.

Good to know that it must work OK then, I've got a ray here and thought it looked a bit weedy compared to the meg and inspo ones I'd looked at previously.

What do they modify on it?

 

[Paul Haynes]

I have the Drager mouthpiece but have yet to use it.
If the strap of the mouthpiece is to go over your crown of your head then what is the preferred setup? Mouthpiece or Mask placed on first as one strap will overlap the other.

For me mask on first then hood (now less chance of loosing the mask or it being knocked off), then retaining strap over hood positioned at the crown to hold the mouthpiece correctly. Rgds Paul

 

[Rickoz]

what 1st

Ok thanks guys thanks for your input :thumbsup:
I think being able to remove BOV to jump on to a OC reg or some other reason means the mask will go on 1st then the OCBOV mouthpiece. Thank you.

 

[Dave Sutton]

Cheers chaps.

Good to know that it must work OK then, I've got a ray here and thought it looked a bit weedy compared to the meg and inspo ones I'd looked at previously.

What do they modify on it?

Internals modified for WOB improvement.

Dave

.

 

[Paul Haynes]

Dang, I knew there was something missing from my Christmas wish list.. ah well will have to get one ASAFP (as soon as financially possible )

Unfortunately, the previous owner of my rEvo cut it off and threw it out :-(

In the mean time try a homemade retaining strap. Garspeed has made his own out of heavy duty elasticated strap, which appears to work well. Perhaps he can post a photograph here. Rgds Paul

 

[paulraymaekers]

In the mean time try a homemade retaining strap. Garspeed has made his own out of heavy duty elasticated strap, which appears to work well. Perhaps he can post a photograph here. Rgds Paul

only problem then is it does not cover the lips correctly, so can leak water in when unconscious

the Dräger bite piece with gag strap is really really very good engineered

Paul

 

[Paul Haynes]

I am not a Crusader, but I like your Crusade and its spirit.

You'll need to write to the CE Technical Committee currently revising the EN14143 standard, because if a requirement for a BOV is not included in the standard, any such addition would be forbidden.

If you wear a BOV and teach, you are breaking HSE requirements on Meg, rEVO, JJ...

Safer and yet, you can't.

Crazy huh?

I really want to avoid corrupting this thread with CE and UK Health and Safety Executive (HSE) discussion and also, as you have subsequently recognised in another post, this thread is not about BOVs. However to address one of your points, which might mislead members who teach professionally in the UK, if your BOV has been tested in accordance with CE Harmonised Standard EN250 (the design and test standard for open circuit regulators), so long as the rebreather is also CE marked, then as a professional diver at work, which a diving Instructor is classed as if he/she receives remuneration for that work, you are compliant with related legislation (modifications excluded). With regards to the HSE diving inspectorate, with whom I frequently interface with on behalf of my clients to address complex diving operations that fall out with the UK Diving at Work Regulations, HSE is there to help diving contractors follow good dive management practice and that they comply with their legal obligations as employers of divers and that divers and diving supervisors do likewise. Also in the event of a diving accident at work, HSE is there to investigate the incident in the same way as the HSE would investigate a builder falling off a roof on a building site or someone loosing an arm in a saw mill. Thankfully the days of the industrial revolution working environment are long gone and we expect to return home safely from a days work and that includes professional divers and diving students under training. In my experience I have found HSE Diving Inspectors, all of whom are ex professional civilian or military divers, to be reasonable, pragmatic people and whilst of course I can not speak on their behalf, any diver at work who uses a none CE marked BOV will be able to convincingly argue that good practice is being followed and they have enhanced diving safety by using the BOV. This argument will be further reinforced if a CE marked off board bailout first and second stage regulator is available to revert to once the initial use of the BOV has been initiated.

This is in my and many others opinion an important safety related thread that has the potential to save life. I'm sure therefore that the majority of the membership will feel the same, please no more HSE / CE talk on this thread, by all means start a new one if you want to but lets not put people off this topic by unnecessary discussion on unrelated bureaucracy that bores the pants of most, including myself. No more shooting from the hip, lets stay on topic. Rgds Paul