Article and flowchart about OxTox Convulsion

Drmike

Hi Dave, can you point me towards a ref for this statement - im having trouble finding anything that supports this claim? (assuming of course you are not refering to a stop in breathing due to drowning)

Some info from DAN
See highlighted sections below;


USN Dive Manual sections 14.9.1.1 and 14.9.1.2 the suggested procedure for dealing with seizures is:

Management of Nonconvulsive Symptoms. The stricken diver should alert his dive buddy and make a controlled ascent to the surface. The victim's life preserver should be inflated (if necessary) with the dive buddy watching him closely for progression of symptoms.

Management of Underwater Convulsion. The following steps should be taken when treating a convulsing diver:

a. Assume a position behind the convulsing diver. Release the victim's weight belt unless he is wearing a drysuit, in which case the weight belt should be left in place to prevent the diver from assuming a face-down position on the surface.
b. Leave the victim's mouthpiece in his mouth. If it is not in his mouth, do not attempt to replace it; however, if time permits, ensure that the mouthpiece is switched to the surface position.
c. Grasp the victim around his chest above the underwater breathing apparatus (UBA) or between the UBA and his body. If difficulty is encountered in gaining control of the victim in this manner, the rescuer should use the best method possible to obtain control. The UBA waist or neck strap may be grasped if necessary.
d. Make a controlled ascent to the surface, maintaining a slight pressure on the diver's chest to assist exhalation.(see commentary below)
e. If additional buoyancy is required, activate the victim's life jacket. The rescuer should not release his own weight belt or inflate his own life jacket.
f. Upon reaching the surface, inflate the victim's life jacket if not previously done.
g. Remove the victim's mouthpiece and switch the valve to SURFACE to prevent the possibility of the rig flooding and weighing down the victim.
h. Signal for emergency pick-up.
i. Once the convulsion has subsided, open the victim's airway by tilting his head back slightly.
j. Ensure the victim is breathing. Mouth-to-mouth breathing may be initiated if necessary.
k. If an upward excursion occurred during the actual convulsion, transport to the nearest chamber and have the victim evaluated by an individual trained to recognize and treat diving-related illness.

Deciding whether to ascend with a diver who is convulsing can be tricky. In section 8-2.4 of Volume 1 of the U.S. Navy diving manual it states:

"If a diver convulses, the UBA should be ventilated immediately with a gas of lower oxygen content, if possible. If depth control is possible and gas supply is secure (helmet or full face mask), the diver's depth should be kept constant until the convulsion subsides. If an ascent must take place, it should be done as slowly as possible. If a diver surfaces unconscious because of an oxygen convulsion or to avoid drowning, the diver must be treated as if suffering from arterial gas embolism."
Obviously, a full face mask is the best way to perform diving with high oxygen mixes because the diver can be kept at depth until the convulsion subsides. If the diver is breathing from a mouthpiece and it comes out of his mouth, there is no option but to surface the diver, since when the convulsion stops he will try to take a breath. Training and practice are the only ways to ensure that divers will know how to bring a convulsing diver to the surface, using a slow, controlled ascent, if that becomes necessary.

In the section on the management of underwater convulsions, the reference to switching the mouthpiece to the surface position would refer only to rebreathers where an open mouthpiece which inadvertently becomes submerged can flood the UBA.

Also, step g should be modified if the victim is breathing nitrox using open-circuit scuba. If someone is convulsing, you won't be able to remove the mouthpiece; and this should never be done by force. Once the convulsion subsides, if the mouthpiece is secure (or if the diver is wearing a full face mask) and if the diver is still in the water and breathing, then leave everything in place until you can get the injured diver out of the water. If he is not breathing, then remove the mouthpiece once on the surface and begin rescue breathing.
The main goal while the injured diver is in the water is to keep him from drowning. Next is to ensure that his airway is open after the convulsion stops by keeping the neck extended.
Finally, be on the lookout for foreign bodies in the trachea. It is possible to bite off the parts of the mouthpiece between the teeth during a convulsion, which can find their way into the trachea, blocking the airway. In these cases, the injured diver will begin coughing as he returns to consciousness, or he may try to breathe but not get any air into his lungs. Here you need to institute the standard procedures taught in CPR classes for foreign body obstruction of the trachea.

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dave t

Hi Mike

I am only talking from first hand experience of the two rescues I have done/assisted. the one I rescued was not breathing when I hit the surface , there was NO water in his lungs (well half a teaspoon) he stopped breathing once more whilst on the boat. The other rescue was done by Kev Gurr, the diver was not breathing when he reached the surface. For this one I was on the boat as was a nurse who started to resuss the victim with sucsess. Also with this one the heart may have stopped but I am not sure on this.
This may not be what happens in most cases but it was what happened to the two I was involved in. maybe I was just unlucky !!!

best

Dave

Drmike

Thanks, I guess you were.

Certainly none of the studies I have read so far have sugested or even mentioned the possibility that an (O2) toxing person would stop breathing after the convulsion phase. Just wanted to double check I wasnt missing something.

"It has been shown repeatedly that apart from the associated hazards of physical injury or drowning, a single oxygen convulsion does not produce harmful or residual effects" Clark and Thom, 'Oxygen Under Pressure' Phys & Med of Diving.

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dave t

can anybody give a FIRST HAND acount of what happens to a diver when he convulses in the chamber, maybe whilst udergoing deco treatment?

Drmike

Heres one report;

JBS Haldane was commissioned by the Royal Navy to follow in the footsteps of his dive-physiologist father. Always an advocate of being one's own rabbit, Haldane subjected himself and his colleagues to various oxygen concentrations under different pressures, noting how long it took before convulsions set in. Exposure to pure oxygen at seven atmospheres pressure led to convulsions within five minutes. He later wrote that:

"The convulsions are very violent, and in my own case the injury caused to my back is still painful after a year. They last for about two minutes and are followed by flaccidity. I wake in a state of extreme terror, in which I may make futile attempts to escape from the steel chamber."

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dave t

that sounds pretty much like what I have seen, pity there is no refrence to time to recovery though. I wonder that the reaction underwater to a convulsion may be more severe in the same way as in a chamber we can tolerate much higher po2's without convulsion.

thanks Mike, anybody got any more?

Dave

Gasman

I enter into this discussion with a certain degree of trepidation. My usual experience of internet discussions is not good. However, there are a few points here that need exploring.
Firstly my back ground. I was trained as an Anaesthetist during which I did an ECT(electroconvulsive therapy) list for about 5 years. I am also a Hyperbaric specialist and as such have witnessed and dealt with a number of O2 seizures.

In the setting of a hyperbaric facility, O2 seizures are stated to be less easily provoked than in water. In our facility, the incidence is about 1:400 @ 3ATA, 1:2000 @ 2.5ATA and less than 1:10000 @ 2ATA. While the incidence of convulsions can be directly related to absolute pressure they do not always occur on the first treatment demonstrating the day to day variability tolerance of the individual to O2. Convulsions are more common in people who have received sedating medications (probably due to CO2 retention) or on specific pain killer such as Tramadol. I bring up the issue of PPO2 and incidence of convulsions because it demonstrates that if a fit does occur, it is likely that the PPO2 will have been quite high (2.5ATA or more) prior to the fit.

As Cedric correctly states, a convulsion has three phases. The Tonic, the Clonic and a post ictal relaxed state. In my experience, the tonic phase only lasts 10-20 second. It is therefore unlikely that another diver will actually witness this phase unless he happens to be looking at the time. This phase is characterised by generalised spasm of all muscles. In the Glottis, this will include both the adductors and Abductors usually resulting in the cords being held in a neutral position. In fact, it is not uncommon for the victim to grunt or vocalise during this phase as air is expelled from the lungs.

The clonic phase follows immediately. During this phase there is rhythmic and uncoordinated, violent contractions of muscle groups. This is the most likely phase to be observed. It is likely that the mouth piece may become dislodged during these movements. This phase is usually described as lasting for a minute or two. But in some cases we have observed it for 5 minutes or more despite being taken off O2. During this phase the muscle contractions result in an increase in CO2, a marked acidaemia and reduction in O2 (though because of the high initial O2 this may still remain above the convulsive threshold). I have ventilated many patients during this phase and never encountered one with a closed glottis.

The last phase is the post ictal phase. The victim will initially be apnoeic and relaxed. They may have another convulsion soon after the first of O2 levels remain high (often about a minute after the end of the first). As I mentioned, if left alone, the victim will often be apnoeic for a minute or two (which may seem forever!) after the fit. From a hypoxia point of view, this is obviously not a problem, but during the fit and the subsequent apnoea, the CO2 has risen quite high. There will cause a strong drive to breath once the respiratory centres in the brain kick reboot. They will usually recover before consciousness returns, causing the victim to hyperventilate. This is where we get into trouble. Up to now, even if the mouthpiece has been out of the mouth, it is unlikely that there is any significant amount of water in the lungs. If the victim breaths at this point with the mouth piece out, he will of course drown unless some kind sole holds some sort of gas delivery system in his mouth.


So what should we do about all of this?

• The convulsing diver is the one with the problem. Don’t make it two divers
• Stay calm, the victim is either not going to expire that second, or is already dead. A calm purposeful response will have a greater chance of success.
• If the mouthpiece is out of the mouth, close it.
• Turn off the O2. Logically, if the diver has fitted, there is something wrong with the unit. We will therefore not use it again. Remember to vent his loop on ascent. If this is too difficult allow the unit to flood. Controlled ascent is a major priority. Venting his drysuit and B/C may cause you enough problems.
• Ascend with the victim to your decompression ceiling. This is not your RGBM / VPM deep stop, nice thought that is! This is the Buhlmann type ceiling which will often be about half the depth pressure (e.g. if you are at 70msw it will often be at about 30 msw). If using a VR3 you can afford to blow off the deep stops. DO NOT PUNCH THE VICTIM no matter how much he has ruined your day! You are going to have you hands full enough as it is! I personally believe that remaining at depth waiting for the convulsion to cease wastes time and increases the chances of another convulsion. Hey, but that’s just my opinion! Ascending reduces the PPO2 as well as the CO2. Both important considerations.
• When the clonic phase stops, put in an O/C regulator (turned on!) of a suitable mix (preferably low O2) in the victim’s mouth and hold it there. As you have ascended the lungs have been venting air so it is unlikely that there is a significant amount of water in them and even if there is at that point, you are not going to do any harm anyway!
• Now the tricky decision bit!
  • Should the victim awake, you can expect considerable confusion and even combativeness. Punching him at this point though therapeutic to you will not help a great deal!
  • Can you pass him up to divers who have completed more of their deco?
  • Do you inflate his B/C and send him to the surface?
  • Do you take him to the surface and then re-descend to complete your deco?

At the end of the day there is no correct decision on this one. It will depend on so many variables that I don’t think any one can say. Personally, if I had a substantial decompression obligation and no one to pass him to, I would attempt to hold him at depth and wait for him to breath. There have been a number of cases of people coming to during deco and completing their time. The important thing is DON”T PANIC!

When you see the Victim in the hospital post event (assuming all is well) then you can punch him all you like!


Andrew

schford

Thanks - very informative - have a blob.

Stuart

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Mdemon

Good post.

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"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"

Dutchy

Isn't this the way that medical protocols get refined over time? Adding newly acquired information, filtering noise and possible redefining the existing standard? I don't want to be stepping on your toes but it sounds as if your preferring theory over practice. At the same time you were curious enought to ask for the source so you're not in denial .
Medical is theory based on empirical data. If you can dismiss of the two incidents because of secondary influences then well OK. If not it could be worthwhile treating the inccidents as a clue in pursuit of refining the protocol. For now it would just be cautious to take the possibility into account...

How? Well that's a different matter. If someone just took the plunge and is toxed right away then a controlled ascent with all measures to prevent barotrauma is not something that I would objected to. For a diver past his NDL it's a different matter I guess and unless we all start diving with black-boxes we might not find the best protocol, just a local optimum.

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