Confusion on the 50/50/50 rule & hypothermia mortality

[shewhorn]

I figured I'd start a new thread on this as there seems to be several versions of the 50/50/50 rule. Someone also mentioned that someone could not survive being in 50 degree water unprotected for 50 minutes. This is not true. The chances of survival depend upon your physiology, metabolism, and the conditions that you're in but people can and do routinely survive submersion in 50 degree water without any thermal protection. In fact, expected survival time for someone in 40 to 50 degree water is 1 to 3 hours (exhaustion or unconsciousness occurs in 30 to 60 minutes), in 50 to 60 degree water it is 1 to 6 hours (with exhaustion or unconsciousness occurring in 1 to 2 hours). Obviously there are many variables and the conditions in which you're experiencing submersion will vary a great deal. If you're in rough seas and you have nothing to hang on to, chances of survival will probably be governed more by the "exhaustion" part of the equation more than anything else. The official cause of death in that case would be drowning and not hypothermia although there is of course a bit of semantics there. Because of exhaustion you can no longer swim, and thus you drown... were it not for the hypothermia... yadda yadda yadda. In calm conditions where you don't have expend as much energy swimming your survival time will go up (because the body's defense mechanism is to stem bloodflow to the extremities and protect the vital organs, the more you move, the more you draw blood flow away from those vital areas and in addition, circulating more blood to the extremities will in effect cool your body even faster).

I don't know what the origin of the 50/50/50 rule is but the USCG version goes something like:

If you're in 50 degree water for 50 minutes you have a 50% better chance of survival if you're wearing a PFD.

Anyhow... I just wanted to put that out there as there seemed to be a bit of confusion. I'm not going to claim to be right but I did do a bit of research before posting just to double check so I think I'm right but if I'm not feel free to correct me. If I'm going to eat my words they ought to be nutritious.

Cheers, Joe

[Michael_Crouse]

You have a 50% chance if you're going to swim 50 yards in 50 degree water.

That's the one I'm familiar with

[shewhorn]

You have a 50% chance if you're going to swim 50 yards in 50 degree water.

That's the one I'm familiar with

That's the one I'd heard (and was familiar with) as well but when I went searching for the source I couldn't find it. I did find the USCG's version. I have a feeling that the USCG's version is the original and the other version got morphed some how through the years. Think about it... 50 yards is less than the length of an Olympic size swimming pool. The survival data does not in any way support that version of the "rule". That's saying 50% of the population would die swimming in 50 degree water for 2 minutes and I just can't find any data that supports that. Surely a small percentage will die, most likely those with cardiac problems but 50% seems highly unlikely given that exhaustion for 40 to 50 degree water sets in at 30 minutes to 60 minutes.

I think I'm going to send this one in to the Myth Busters!

Cheers, Joe

[shewhorn]

Ha! I posted a suggestion to the Myth Busters and I also fired off a question to the USCG SAR. I doubt the Myth Busters will do a piece on it and I'm not sure the USCG will respond but there you have it.

[spuglisi]

Ha! I posted a suggestion to the Myth Busters and I also fired off a question to the USCG SAR. I doubt the Myth Busters will do a piece on it and I'm not sure the USCG will respond but there you have it.

I'd love to see myth busters tackle that one. Maybe you should have suggested they blow something up before people wind up in the water. I think that would make it irresistible to them.

[shewhorn]

I'd love to see myth busters tackle that one. Maybe you should have suggested they blow something up before people wind up in the water. I think that would make it irresistible to them.

Hmmm... "I've heard that divers use sticks of dynamite to keep warm and avoid hypothermia. I was talking to a diver friend and they said C4 was far more effective for keeping warm... it's also a good way to go fishing... apparently"

[djlewis]

That's the one I'd heard (and was familiar with) as well but when I went searching for the source I couldn't find it. I did find the USCG's version. I have a feeling that the USCG's version is the original and the other version got morphed some how through the years.

50 degree water, 50 minutes, 50% chance of survival -- that's the one I remember.

Who cares if it's 100 minutes and 25% chance of survival. The point is that 50 degree water is deadly.

If you are not wearing immersion clothing (wet or dry suit) and cannot get out of the water (into your boat, say) you might very well die, right then and there.

So you absolutely need a way to get back into your boat -- that's why we equip for and practice re-entries, assisted and self. And to give yourself a fighting chance in case reentry is difficult, say you are waiting for assistance, you wear protective clothing. In any case, you must wear a pfd, or as soon as you lose limb function (which is a lot sooner than death) you will just sink and drown, and never get the opportunity to die of hypothermia per se.

Thus, the logic of basic safety technique and gear!

--David.