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solution to the problem of
Shallow Water Blackout
Alarm systems to prevent death by fainting underwater
The phenomenon known as Shallow Water Blackout or Latent Hypoxia, as described at such pages as http://en.wikipedia.org/wiki/Shallow_water_blackout and http://scuba-doc.com/latenthypoxia.html , is a problem where people effectively faint underwater, often resulting in drowning. The problem occurs apparently without warning, and is strongly associated with the practice of hyperventilation (breathing a lot before holding your breath). There's a lot of scare stories about this, and what doesn't help is the over-reaction where various people are trying to ban this or that for people's own good. That's not a good approach to safety. Much better is the idea of danger-management.
The problem of fainting underwater may seem a terrible and insidious form of lurking death, especially as it comes with no warning. However, the same sort of thing could have been said about the mysterious phenomenon of people being found dead in their beds after a fire, apparently unaware they were being burned! That old problem was later solved by the discovery of the mechanism by which they died: They died in their sleep by inhaling smoke. The cure was the invention of smoke alarms, which make a loud noise if there's smoke, thus waking people up so they can flee from the fire. Smoke alarms are a good idea and can save your life. See DIY Stores for places where you can get them. Also see carbon monoxide detectors.
Meanwhile, underwater, the problem of Shallow Water Blackout may have a similar cure. Now although it's generally believed that hyperventilation is the problem and has things about it which work rather differently to that which was first imagined, I have reason to believe things aren't quite as simple as that. If that were the case, then it would be possible to fall unconscious IN AIR by hyperventilation and then holding your breath. In experiments I have found that for myself this is not possible, at least not without standing up suddenly, or other techniques designed to cause momentary unconsciousness. So, I suggest that the actual problem of Shallow Water Blackout may have a more complex mechanism, and may have a cure which is a bit like the smoke alarm.
In most of the reported cases of Shallow Water Blackout, the victim is found lifeless at the bottom of a swimming pool. I have performed experiments and found that usually no-one notices a person lifeless at the bottom of a pool. I'm not bad at holding my breath, and I am heavier than water, and I have found I can rest on the bottom of a pool for a couple of minutes even in a crowded resort and no-one really notices. Therefore I can conclude that cases of Shallow Water Blackout remain unnoticed for many minutes before being discovered, by which time it may be too late, as the person has died of drowning and it's too late to recover them.
In my quest for a cure for the problem of Shallow Water Blackout I asked such places as Simply Scuba about oximeters. What I mean is, those optical blood-oxygen measuring devices which fit on an ear-lobe. Sure enough, an ear oximeter is not expensive, and it may yet be possible to construct such a device to work underwater, and to be small enough to be more like an earring than a beltpack hi-fi. The idea is that like with the smoke alarm, unconsciousness is no impediment to an alarm system. The differences with the blood oximeter are rather more involved, but let's get to that later. In principle, the idea is that upon losing consciousness underwater, the blood oximeter starts to read low blood oxygen levels. In fact, it may be possible for the oximeter to trigger an alert before the person loses consciousness! This could prevent the problem of their subsequent drowning.
Next, in this new life-saving device, the low blood oxygen triggers an alarm, which is sensed underwater and by a radio link on the surface. Underwater radio links are possible (submarines communicate by VLF radio), and the technical difficulties of attenuation can be solved by consideration of the dB and the frequency characteristics of a medium, etc.
In "attended mode" the job of the alarm system is largely complete. It remains for someone to fish the person out of the water and resuscitate them, but with the alarm ringing within seconds of the low blood oxygen level, recovery is clearly possible.
Further to the idea of "attended mode", I had figured that in a public pool, various people wishing to practice free-diving and yet having themselves some assurance of avoidance of drowning, could leave their SWB-monitor receivers under the lifeguard's seat. Someone has pointed out that the system could be simplified by the pool having one receiver system for all, but I suspect that it would then be a matter of the pool owners investing the money, whereas in the "many users" system, it's up to each person to bring along a receiver, and their life is their own responsibility, which is how it should be.
I have also devised an "unattended mode" of operation of the device. This is more complex, and involves several systems, but it could save people from drowning alone in their own pool. I am keen on this type of safeguard, and you can see why when you understand that I am a diabetic and I live alone and I have nearly died of hypoglycaemia. On many occasions I have nearly died alone, so the idea of saving people from a lonely death is something which I have sympathy with. So, there is this additional page of SWB Cure Unattended-Mode if you're interested in reading about the crazy invention.
Meanwhile, the idea of people being able to indulge in hyperventilation, holding breath underwater, freediving, and other such things, needs to be preserved for the sake of freedom of action and taking responsibility for your own danger/safety. People don't take it in shifts to stay awake in a house on the grounds there might be a fire. They rely on the smoke alarms to wake them up and save them. Similarly, this Shallow Water Blackout avoidance system is like an "underwater smoke alarm" which saves people before they know they are in danger!
No, I do not yet have any of these things for sale. However, I know the principles and I am willing to help to get this idea developed and made into a publically-available device to help to save people's lives. So, the idea is published as a shareware invention, and if you want to get in touch here's the contact. As with the hearing aid with street cred, it's a device which can be built and marketed.