Hello John,
This was one of the more difficult issues. As you correctly point out there is a long standing belief that bringing a diver to the surface during a seizure is dangerous because the glottis (the airway at the larynx) will be closed and the airway will be blocked. This would create a risk of pulmonary barotrauma because air would be prevented from escaping from the lungs during the ascent. That is the basis for the long held belief that one must wait until the seizure has finished before bringing the diver to the surface.
However, there are some other facts that are important.
First and most importantly, the assumption that the glottis is inevitably closed during a seizure is incorrect. We see sometimes see non-diving patients suffering "status epilepticus" which essentially means a seizure that does not terminate, and which may continue for a long time. If the airway were closed in this setting it would be a non-survivable event but the vast majority of patients survive prolonged seizures. Moreover, I (and many of my anesthesia or ER colleagues) have been able to manually ventilate such patients with a bag - mask during a seizure which, again, means that the airway is not completely closed. In addition, we obtained a video of the glottis in pigs during a seizure which showed that although there is certainly a partial and rapidly fluctuating obstruction of the glottis during a seizure, it is also open on a rapidly fluctuating basis.
Second, the first thing that a patient starts to do after a seizure (but while still unconscious) is to start breathing heavily. If they did that with an unprotected airway underwater, then they will inhale water and drown.
If you put these two facts together, then it is possible to draw the conclusion that the period when a diver is seizing but not breathing may actually be the correct time to bring them to the surface, because if you hold them underwater until the seizure finishes and they start to breathe, then they will almost certainly drown. This is particularly true if the airway is unprotected (regulator out) and our conclusion was that in this setting the risk of pulmonary barotrauma in bringing them to the surface was less than the risk of drowning by holding them underwater until the seizure had finished.
We gave different advice if the regulator or mouthpiece or full face mask was still in place. We could argue about how much "airway protection" is provided by a regulator held in place, but we thought that if the reg / mouthpiece remained in place and the rescuer could hold it there, then the balance of risk would shift in favour of waiting until the seizure had finished before bringing the victim to the surface. In this setting, it is anticipated that if the victim starts breathing then they are much less likely to drown because the reg / mouthpiece is still in place.
That is the logic behind the recommendations around seizures.
Simon M
