There are well known dangers of high altitude climbing. Once you climb above 8,000 meters, your body begins to die. Even with bottled oxygen, you are still dying. The reason is the partial pressure of oxygen is not enough to supply oxygen to all the bodies tissues. To survive you need a pressure suit. For safe high altitude climbs, you need a base camp to make decisions for climbers, and the climbers need to do as they are told. Brain swelling, and pulmonary edema will happen to everyone if they stay above 8,000 meters long enough.
I am not a deep water diver. My dives were all made in chamber rides for medical reasons, Medical Hyperbaric Chamber Dives. The risks at depth are the opposite of high altitude climbs. At depth, the partial pressure of inhaled gasses climbs. The greater the partial pressure is, the more inhaled gases will be dissolved by force, into the circulating blood serum. The first worry is Nitrogen that is found in compressed air. With the increased partial pressure of the nitrogen in common air supply, the result is nitrogen narcosis. The result is like drinking a bottle of Bushmills on the way down, and it can kill you. Deeper down, Oxygen itself becomes a problem. As the partial pressure of Oxygen rises, so does the risk of Oxygen reaching toxic levels. The most common result is Gran Mal Seizures. Every dive I went on was with patients on oxygen, and the worry was always toxic levels of Oxygen. We had all decisions made outside the chamber. Each med we gave was watched, and triple checked with staff outside the chamber. I think the divers need the same links I had during chamber rides, and the high altitude climbers have with a base camp making calls. The other problem is the air mixtures divers are using at depth:
The Search for the Perfect Gas. Again, I am not a certified diver, just a chamber diver, but; even using the Dragger rebreather systems, I have to wonder if the partial pressure of rebreather oxygen is too high?
I am sorry to hear of the loss of the divers.
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