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  1. #1
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    Ascent rate for CBL

    One of our instructors insists that trainees should be taught to bring up a victim at the standard BSAC ascent rate of 1 minute for the last 6m. He makes them take 30 seconds to bring the victim up from the bottom of the 3m deep pool that we use. In a real life situation, I would have thought it more sensible to use a faster ascent rate to get a non-responsive diver to the surface as soon as practical subject to not causing a massive risk of DCS. If a diver becomes unresponsive shortly after beginning a dive to 10m, there is very little risk in a fairly fast ascent but obviously if the diver is well into deco, the risk is rather different.

    BSAC instructor info is not very clear about this subject, at least not that I can find and I would be pleased if anyone can point me to the appropriate instructions.

    What does TDF think should be taught?

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    Guidance form BSAC is as follows:
    "While the object, for training purposes, is to maintain an ascent rate that is as near to the normal rate as possible, it has to be anticipated that this rate may be exceeded. (For real life rescues, the priority is to ensure that the casualty is successfully recovered to the surface."

    So when it applies to real life situations to me it's important to illustrate the risks of ascending faster than usual, and to assess the situation based on where the dive is, surface cover, and if you buddy appears to be breathing etc, if you're 3000 miles away from a decompression chamber then resuscitation after spending a slightly longer period under water may be easier than dealing with two divers with a bend.

    When it comes to the training the CBL is halted at 6 meters so there is no issue, it might be less for Ocean Diver, haven't done that one in a while.

  3. #3
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    Here is the UHMS report on the subject of surfacing an unresponsive diver:
    http://deepadventurescuba.net/assets...aterrescue.pdf

  4. #4
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    Quote Originally Posted by ManualOverride View Post
    Guidance form BSAC is as follows:
    "While the object, for training purposes, is to maintain an ascent rate that is as near to the normal rate as possible, it has to be anticipated that this rate may be exceeded. (For real life rescues, the priority is to ensure that the casualty is successfully recovered to the surface."

    So when it applies to real life situations to me it's important to illustrate the risks of ascending faster than usual, and to assess the situation based on where the dive is, surface cover, and if you buddy appears to be breathing etc, if you're 3000 miles away from a decompression chamber then resuscitation after spending a slightly longer period under water may be easier than dealing with two divers with a bend.
    That is very much how I have always interpreted it but the training info is a bit thin with regards to guidance as to how a CBL situation should be assessed. The 1 minute from 6M to the surface I think is unrealistically slow in a life-threatening situation and I think would place more emphasis on the risks of DCS than on getting a casualty to the surface.

    The reason I asked was that we were doing the SD pool training last night and one of the trainees was asking about what an acceptable 'faster than normal' ascent rate was and I couldn't find any guidance to point them at. I do wonder whether the old 'don't ascend faster than your small bubbles' (which is quite fast by modern standards) might not be a bad guide.

    OD and SD training both involve taking the casualty to the surface, making buoyant and towing, SD includes rescue breaths as well.

  5. #5
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    Quote Originally Posted by Allan Carr View Post
    That is very much how I have always interpreted it but the training info is a bit thin with regards to guidance as to how a CBL situation should be assessed. The 1 minute from 6M to the surface I think is unrealistically slow in a life-threatening situation and I think would place more emphasis on the risks of DCS than on getting a casualty to the surface.

    The reason I asked was that we were doing the SD pool training last night and one of the trainees was asking about what an acceptable 'faster than normal' ascent rate was and I couldn't find any guidance to point them at. I do wonder whether the old 'don't ascend faster than your small bubbles' (which is quite fast by modern standards) might not be a bad guide.

    OD and SD training both involve taking the casualty to the surface, making buoyant and towing, SD includes rescue breaths as well.
    The lines I quoted was from the dive leader instructor notes, which seem to give much more detail. That was a very good question from your student, and the answer very much is it depends. To a Sports Diver I would outline the risks and mitigating factors, they will potentially be doing unsupervised deco dives so it needs to be made clear the added risk that would be added if they missed stops and ascended faster than usual under high tissue loads. Obviously no significant testing is done on faster ascents because people don't regularly do them so you can't give them a figure, and you also can't advocate a course of action that has a high chance of causing harm. How fast they ascend is up to their judgement in the situation they find themselves in. I would however have no problem running through examples of what I would do.

    If I was doing a charity dive with the girlfriend in the pond of a local hospital that happened to have a re compression chamber where the shore was lined with pensioners in wheelchairs stacked with O2 and doctors cheering us on, and 2 minutes in to the dive she became unconscious at 10m and spat out her reg I'd shoot out of the water like a Polaris missile. (Ok maybe not that fast, but fast)

    If it was the wife I'd probably do another couple of laps of the pond. You've got to read the situation and think whats best.

  6. #6
    bottlefish Stuart Keasley's Avatar
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    PADI guidelines are a controlled ascent, performance requirements (from memory) are to ascend at a safe ascent rate.

    In contrast, when I completed my commercial course, it was get in, get down as quick as as you can, get them up as quick as you can, we can always throw you in the pot if we need to.

    As above, the answer depends, on the factors and risks involved, what support and facilities are there for you.... but always err on the side of caution. Doubling the amount of casualties they need to deal with topside, halving the amount of oxygen etc is not going to do anyone any favours.
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    If you are talking about a non-responsive (unconscious) diver underwater rather than a toxing diver underwater, you are essentially recovering a corpse in the hope that it can be brought back to life on the surface. The ability to revive that corpse depends upon a number of things, one of which is the speed with which you can get the diver to the surface and the chance for effective first aid.

    Who benefits from a 1 minute ascent from 6 meters? The corpse? The rescuer?

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    Consider this scenario, which is a key part of most rescue training:

    1. The rescuer comes upon a non-responsive diver and takes steps to ensure that the diver is non-responsive and not just taking a nap.
    2. The rescuer brings the victim to the surface in a controlled manner.
    3. the rescuer makes both victim and self buoyant.
    4. The rescuer puts the victim on the back.
    5. The rescuer determines that the victim is not breathing.
    6. The rescuer tells bystanders to contact emergency services.
    7. The rescuer begins rescue breaths.
    8. While doing rescue breaths and while towing the diver to the nearest solid surface, the rescuer slowly removes the victim's and his or her equipment.
    9. The victim arrives at a solid surface and is taken out of the water.
    10. The victim revives.

    I have many times in the past asked if anyone can supply the details of a case in which this procedure was followed and resulted in a successful revival of the victim. I have never heard of such a case.

    In the closest case I know if (described to me by a friend who was there), a diver was seen slipping below the surface. A DM jumped in; swam to the site; free dived down; got to him at about 20 feet; grabbed his arm; swam to the surface as fast as possible; swam as fast as possible to the boat, dragging the unconscious body behind him; got him on the boat; and revived him almost immediately with CPR.

  9. #9
    bottlefish Stuart Keasley's Avatar
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    Quote Originally Posted by JohnAdsit View Post
    If you are talking about a non-responsive (unconscious) diver underwater rather than a toxing diver underwater, you are essentially recovering a corpse in the hope that it can be brought back to life on the surface. The ability to revive that corpse depends upon a number of things, one of which is the speed with which you can get the diver to the surface and the chance for effective first aid.

    Who benefits from a 1 minute ascent from 6 meters? The corpse? The rescuer?
    Do you think bolting to the surface, adding a second casualty to the first will improve the likelihood of a positive outcome for the first?
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  10. #10
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    Quote Originally Posted by Stuart Keasley View Post
    Do you think bolting to the surface, adding a second casualty to the first will improve the likelihood of a positive outcome for the first?
    In logic, this is called a false dilemma. Your question assumes there are only two choices, and the rescuer has to choose one or the other.
    Choice One: Extremely slow
    Choice Two: recklessly fast, with the rescuer holding his or her breath the whole time and getting an embolism

    Actually, there are other choices. The most common ascent rate today, the one favored by the Bühlmann algorithm, is faster than choice one. The old US Navy rate that is still listed as the standard ascent rate for PADI tables is 3 times faster than choice one. Many people ascend at those rates and live to tell about it.
    Last edited by JohnAdsit; 09-05-2019 at 07:49 PM.


 
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