We all know (or should) that breathing high oxygen levels underwater can be very dangerous and beneficial at the same time. High oxygen levels reduce decompression obligations. Decompression patients, commercial, and military divers are routinely exposed 100% oxygen at 60 FSW pressure equivalent in a chamber — a PPO2 of 2.82 ATA or more than twice the recommended MOD (Maximum Operating Depth) for recreational divers.
It is a safe and accepted practice because divers under close supervision and even the most dangerous OxTox (Oxygen Toxicity) symptoms are manageable — what the heck is that supposed to mean? Compared to in-water stops, here are the biggies:
Hypothetically, what if you determine that exposing divers at water stops to higher levels of oxygen would outweigh the risks? All the reasons I can envision start with choosing to make dives without quick access to a treatment chamber. They include:
What exactly could you use this “system” for? These conditions come to mind:
The question then becomes how can risks be minimized and/or mitigated (assuming you decide to dive there anyway and can’t afford the chamber and the vessel to put it on)? I contend that the answer is “not much” unless the diver can be brought under some level of supervision and have access to more gear than they can swim with. This may not be out of the question for divers that can reliably return to the boat or some other way-station.
What would it take? These random thoughts come to mind:
Supervision: As a minimum, that means two-way communications. That could mean a FFM with audio communications to a topside supervisor, which may as well be hard-wire. Considering how inexpensive TV cameras are today a camera may also be included.
Intervention: Supervision without intervention is useless. Ideally the supervisor must be able to switch the diver(s) between pure O2 and air. This automatically puts breathing gas management under topside control where logistics are more easily managed. Depending on the situation, a standby diver ready to jump in seconds and/or a safety diver tending the divers on O2 are necessary.
Barf Management: A FFM is much better than a mouthpiece for communications and comfort, but isn’t without risk since vomiting is a common OxTox symptom. A commercial diving helmet would be a big improvement, but switching to one underwater is challenging (aside from being very expensive and requires considerable training).
Convulsion Management: A convulsing diver is better off in a FFM, and even better off in a commercial diver’s hat. There is a high probability that they will recover after being switched to air, but the air-way obstruction risk remains. Commercial hats are pretty tight to offer assistance but at least the diver won’t drown as long as they are kept upright.
The last two issues got me thinking. Instead of a FFM or commercial diving helmet, what about an open-bottom hat/mini bell that is permanently rigged. Sort of a cross between an old Miller Dunn helmets and one of those tourist diving helmets.
Swim, up, stick head in, sit or snap harness in, and switch from your demand regulator or rebreather mouthpiece to an oxygen oral nasal. It could be pretty light-weight for transport, but would be in the 50-100 Lb range (per hat) with enough lead to sink it.
So why did I post this? Reality checks are always good, online design reviews are stimulating, and hopefully all of us will learn something. Besides, the diving here is lousy today.
It is a safe and accepted practice because divers under close supervision and even the most dangerous OxTox (Oxygen Toxicity) symptoms are manageable — what the heck is that supposed to mean? Compared to in-water stops, here are the biggies:
- They can quickly be switched to air when any symptoms are suspected or observed
- They are far less likely to aspirate vomitus and/or drown
- They are far less likely to physically injure themselves and/or drown if they convulse
- They are under less physical and mental stress, can hydrate, and maintain thermal comfort… not sure what role dirty magazines play but it seems to be standard equipment.
- For hyperbaric treatments, a trained attendant is sitting next to you.
Hypothetically, what if you determine that exposing divers at water stops to higher levels of oxygen would outweigh the risks? All the reasons I can envision start with choosing to make dives without quick access to a treatment chamber. They include:
- Diving off a liveaboard, hours or days from an operational hyperbaric chamber and an aircraft to get you there. DCS risk is much higher doing 4-5 dives a day for a week than two dives every few Saturdays.
- Expedition dives. There are a large number of virgin wrecks that are deep, but in warm calm water… and in the middle of nowhere.
- Scientific and archeological surveys
- Let’s not forget my personal favorite, treasure hunts
What exactly could you use this “system” for? These conditions come to mind:
- Accelerating normal decompression to reduce thermal and/or elapsed time stress
- Increasing safety margin for normal decompression — use higher O2 levels than the decompression profile prescribe
- Prophylactic oxygen treatments — return “symptom free” for additional water stops without taking credit in your decompression profile. Useful when you can’t reliably return to the boat without surfacing.
- IWR (In-Water Recompression). Before everyone gets their underwear in a twist; let’s all agree that it is very dangerous, should only be performed under very limited conditions, and with only very competent people. You may well be choosing whether to die trying or not.
The question then becomes how can risks be minimized and/or mitigated (assuming you decide to dive there anyway and can’t afford the chamber and the vessel to put it on)? I contend that the answer is “not much” unless the diver can be brought under some level of supervision and have access to more gear than they can swim with. This may not be out of the question for divers that can reliably return to the boat or some other way-station.
What would it take? These random thoughts come to mind:
Supervision: As a minimum, that means two-way communications. That could mean a FFM with audio communications to a topside supervisor, which may as well be hard-wire. Considering how inexpensive TV cameras are today a camera may also be included.
Intervention: Supervision without intervention is useless. Ideally the supervisor must be able to switch the diver(s) between pure O2 and air. This automatically puts breathing gas management under topside control where logistics are more easily managed. Depending on the situation, a standby diver ready to jump in seconds and/or a safety diver tending the divers on O2 are necessary.
Barf Management: A FFM is much better than a mouthpiece for communications and comfort, but isn’t without risk since vomiting is a common OxTox symptom. A commercial diving helmet would be a big improvement, but switching to one underwater is challenging (aside from being very expensive and requires considerable training).
Convulsion Management: A convulsing diver is better off in a FFM, and even better off in a commercial diver’s hat. There is a high probability that they will recover after being switched to air, but the air-way obstruction risk remains. Commercial hats are pretty tight to offer assistance but at least the diver won’t drown as long as they are kept upright.
The last two issues got me thinking. Instead of a FFM or commercial diving helmet, what about an open-bottom hat/mini bell that is permanently rigged. Sort of a cross between an old Miller Dunn helmets and one of those tourist diving helmets.
Swim, up, stick head in, sit or snap harness in, and switch from your demand regulator or rebreather mouthpiece to an oxygen oral nasal. It could be pretty light-weight for transport, but would be in the 50-100 Lb range (per hat) with enough lead to sink it.
So why did I post this? Reality checks are always good, online design reviews are stimulating, and hopefully all of us will learn something. Besides, the diving here is lousy today.
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