There is a proverb in business, and in life generally, that if you don't know where you are going, any road will do. But if you have a particular end in mind, then some roads are better than others.
This proverb applies doubly with respect to man overboard. Prior to evaluating various boat handling and recovery techniques, we must give thought to the state in which our casualty is going to be, and the extent to which he is likely to be able to assist in his own rescue.
In pretty well 100% of Canadian waters, this means we need to understand hypothermia.
I had the opportunity for an extended discussion about hypothermia with Nathan Webb, an instructor for the Coast Guard Rescue Specialist program. According to Nathan, the Coast Guard understands the scenario people face when going into cold water in terms of
1-10-1. 1:Your chance of drowning during the first minute is quite high.
During this time, there is an involuntary hyperventilation that goes on, and it is REALLY easy to inhale water, gag and drown. The other possibility during that first minute is simple cardiac arrest. So swimming ability is not hugely relevant during this minute.
The risks inherent in this first minute help one understand the strong Coast Guard recommendation to never put a second person in the water try to assist in the rescue of the MOB. You could end up with two dead people in the water rather than just one.
Practical Sailor magazine discusses this first minute in a bit more detail in their article on "cold water shock."
10:If you can survive the first minute of immersion, you have 10 minutes of usable time where you can assist in your own recovery.
For instance, you could climb up a boarding ladder if one was available to you. After these 10 minutes are up, hypothermia will have set in enough that you will not be able to grip anything with your hands.
This assumes you were wearing a PFD when you went into the water. If you have no PFD on, you "can stay afloat for about 5 minutes and then will drown" (Transport Canada Report on Cold Water Survival, p. 64). 1:You can survive in the water for one hour.
You can't assist in any way in your own rescue, but you are alive (assuming you have that PFD on). After one hour, you die. If you elect to try swimming, you die sooner. Swimming dramatically accelerates the progress of hypothermia.
These times are based on water at 0 to 6 degrees C. With warmer water, the times for usable-activity and survival will lengthen. I was discussing these points with Bill Anderson, a friend of mine who lives in BC, via email, and he wrote the following:One time, on Maligne Lake, after a day of kayaking in the hot sun in a wet suit, I decided to practice my self rescue. Since I was going to be close to shore and I didn't want to get the wetsuit soaking, I just set off in my shorts and long sleeved shirt. Over I went, no problem, done that many times. 15 seconds later, it was a problem. 60 seconds later, I crawled out of the water, gasping.
That first 1 minute rule is bang on.
If you have practiced boat-handling strategies for getting back to an MOB, you know that it is difficult to have your boatspeed drop to 0 knots just at the moment you come alongside the casualty, and do it on the first pass. You often end up having to go around a second, or even a third, time. It is painfully easy to absorb 8 to 15 minutes during this stage of the rescue.
In light of what we know about hypothermia, it is clear that by the time we are ready to start getting the casualty back on the boat, we must be prepared to proceed without any assistance from the MOB himself. Even in perfectly calm water, having him climb up the swim ladder may be impossible.
But it gets even worse. In 2008, Gillian West, a round the world, solo-sailor who has shaped the instructional programs for both Sail Canada and the American Sailing Association, said, "When the Lifesling first came out, we all thought it was the answer to our prayers for MOB recovery. But then we discovered that hypothermic people, when lifted vertically, often go into cardiac arrest."
What Gillian was alluding to was the tragic 1994 sinking of the passenger ferry Estonia in the Baltic Sea. "Following the sinking, about 300 people, all wearing lifejackets, were in the water.... Helicopters winched only those that had signs of life, in a vertical position. Many died from circum-rescue collapse, resulting from severe hypothermia.” (http://www.sarrrah.de, retrieved Nov. 13, 2013)
Nathan Webb, of the Canadian Coast Guard, unpacked a bit more of what we have learned since then about
hypothermiaand vertical rescue. He says: The circum-rescue collapse, where a casualty goes into cardiac arrest during or immediately after their rescue has 3 causes (two physical and one mental/emotional). The first, as you have noted, occurs as the casualty is hoisted vertically out of the water into the helicopter or vessel. While the casualty is in the water, the water pressure pushes on the body and helps them keep blood in their body core. When they are lifted out of the water in a vertical position, the body isn't ready for the loss of external pressure, and the blood begins to pool into the legs and lower body. If they are lifted for a long time or to a large height, the brain and heart will lose blood and thus cause cardiac arrest. This situation is usually more evident when hoisted into a helicopter or up to the deck of a deep sea vessel. The second physical cause, is due to the cold, acidic (Bob's comment: "acidic" blood = CO2-rich; oxygen-poor) blood from the extremities being sent all at once back to the heart. The heart of a severely hypothermic casualty is "tender" and susceptible to injury, the cold blood hitting the heart puts it into arrest. Both of these situations are dealt with by lifting or hoisting the casualty in a horizontal position and treating them as gently as possible.... The emotional cause for circum-rescue collapse happens when a casualty hangs on until the feel they are rescued, then relaxes. The body has amazing coping strategies and as long as the casualty thinks they need to fight to stay alive, the body will work hard to do so. If a casualty is rescued and told that they are safe and okay, sometimes they will completely give out due to fatigue and stress. This causes the body to relax and subsequent cardiac arrest. When we train our Rescue Specialist, we tell them to talk to the casualties and tell them to keep fighting until they have been warmed up or have reached the hospital. Usually just talking with a casualty and encouraging them gives them the boost they need to keep going.
http://www.beyondcoldwaterbootcamp.com/en/glossary-references/113-circum-rescue-collapse goes a bit further in describing the physiology of this emotional component when they say: "...Stress hormones may also play a role. In this case, these hormones increase muscle strength and help maintain blood pressure during cooling. However, the rescue process could decrease the levels of these hormones due to mental relaxation, and that could cause a decrease in blood pressure."
An aside from Bob: If you want to research a bit more about stress hormones, the three that you want to read about are adrenaline, cortisol, norepinephrine.
If a Lifesling is all the retrieval equipment you have available to you, of course you use it! Better out of the water than in! But if you go into cardiac arrest during your rescue, you are just as dead as if you drowned.
Better yet is to retrieve the casualty in a horizontal position. More on this on the Recovery Methods page.
If you are like me, you got some training in the Boy Scouts that said a good first aid treatment for hypothermia was "shared bodily warmth" - which usually meant climbing into the same sleeping bag as your casualty. Nathan Webb had some forceful cautions about this.
I would strongly urge against using shared body heat as a source for re-warming a casualty. This should be only as a last ditch effort when there is absolutely no other way to warm the casualty. There are multiple problems with this method: the warming person will inevitably jostle the hypothermic person, causing cold blood to go the casualty's body core; the warming person will be losing their heat, and may also become hypothermic, thus creating another casualty; if there is only one person to help, they will need to get in and out of the sleeping bag periodically to talk on the radio, look after the boat, and do a number of other tasks, causing more jostling and exposing the casualty to cold air every time the person gets in and out of the sheets.
Whatever strategy we use to handle an MOB emergency should be flexible enough to manage this worst-case scenario:
- We need something that works where a couple is sailing together, where the man is heavier and stronger, and the more skilled sailor...and is the one that has gone overboard.
- That is to say, we need boat handling and personal-recovery to work where the weaker, lighter, less skilled sailor can perform a recovery on her own, single-handed, to retrieve a person who is heavier than she is.
- We must have a strategy that works where the casualty in the water is completely unable to assist himself in his own rescue. This may not only be because of hypothermia alone, but because the casualty might have been hit in the head by the boom during an unexpected gybe, and has been knocked unconscious.
If your MOB strategy can meet these challenges, then if you are crew-heavy with skilled sailors and a fully conscious casualty enjoying warm tropical waters, of course it just gets easier and easier. But in Canadian waters, you simply
cannot approach rescue the same way your would if you were sailing off the coast of Cuba.
I will refer to these elsewhere on this website, but let me take the opportunity now to point you to two helpful documents:
Transport Canada Report on Cold Water Survival.pdf (9.6 MB)
2005 Crew Overboard Rescue Symposium.pdf (1.1 MB)