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It has now become clear that over half of the immersion-related deaths occur during the first two stages of immersion, i.e. cold shock and swimming failure. However, as stated previously, investigators still concentrate on the cause of the marine accident and not the precise cause of an individual’s death. It is still hard to accurately document at what stage of the immersion death occurred. This is because little history has been gathered from survivors or by investigators. It is only possible, to a limited degree, to estimate the cause of death from a newspaper report or the scant information in the accident investigation. The problem is further compounded by the fact that such a good job has been done educating people on the dangers of cold water, immersion and hypothermia, that even the pathologists now list the cause of death as hypothermia, even though the cold, wet body on their autopsy table actually died from cold shock or swimming failure and drowning.

The author was concerned about the Canadian general public’s ignorance of the dangers of cold shock and swimming failure. Therefore, in conjunction with the Canadian Navy and the National Search and Rescue Secretariat, he produced, in 1998, a new training video on this topic titled "The Cold Facts – Surviving Sudden Cold Water Immersion". It is now available from Intercom Films in Toronto. As a follow on to this, he updated the knowledge on hypothermia and post-rescue collapse with the same sponsorship. The new video, "More Cold Facts – Hypothermia and Post Rescue Collapse", will be available in August 2001.

Furthermore, there has now been more research done on loss of tactility in cold water during the first 10-15 minutes of immersion (Reference 68). During this time, the cold water renders the limbs useless, and particularly the hands. It can become impossible to carry out any self-rescue procedures. This only enhances the possibility of perishing before hypothermia is established.

STAGE 1 – COLD SHOCK ^

Although cold shock or an increased respiratory response to cold water has been known for many years (Falk 1884) (Reference 10), the practical significance of this response has only really been evaluated in terms of its practical importance in the last 20 years. When considering at what water temperature protection should be provided against the initial responses to cold water immersion, it is now known that the cold shock response begins at water temperatures below 25ºC (Reference 33) and peak at a temperature between 10-15ºC. (Reference 60, 61) This is in part, the explanation for deaths that occur in water as high as 15ºC long before standard survival curves would predict. It is now thought by many that the pressing threat to otherwise healthy individuals is the respiratory distress evoked by immersion and the consequent inability to control breathing and breath hold.

Breath Holding Ability And Ability To Control Breathing Rate ^

This is very critical for all who abandon ship into cold water. If they abandon dry shod into a liferaft, there is no problem. However, if they abandon ship into cold water, unless they are mentally and physically prepared for the cold shock, are protected with a survival suit, a lifejacket and a spray hood, they may drown in the immediate abandonment due to the inability to control breathing in the first three minutes of immersion. It is not just a problem of not being able to breath hold; if you are in choppy water, there is an inability to coordinate and control breathing with wave splash. This is a typical scenario for passengers on tourist vessels in Canada’s lakes and rivers in spring and early summer.

Sterba et al (1979) (Reference 54) investigated breath holding capability of humans in water ranging from 15ºC-35ºC. They concluded that breath holding ability at 15ºC was approximately 30% of the non-immersed values.

Hayward et al (1984) (Reference 27) showed clearly that there is an inverse relationship between water temperature and breath hold ability. Thus, for abandonment in 25ºC water, average breath holding is 38 seconds, whereas for 15ºC, 10ºC and 5ºC water it is 28, 24, and 19 seconds respectively. They concluded that breath holding time in water below 15ºC was 25-50% of the presubmersion level. Their predictive curve was recently validated at the higher end of the scale by Cheung et al (2001) (Reference 6) in 25ºC water following a breath holding experiment. Two hundred and twenty eight subjects participated and the average breath hold time was a mean of 39.8 ± 21.1 seconds.

The ability to do such tasks as activate the life jacket inflation device (if fitted), climb into a life raft, cling to a becketted line or activate a flare depends on manual dexterity and grip strength. The ability of muscle to produce force is reduced when its temperature falls below 27ºC. This can occur in as little as 20 minutes in water at 12ºC. (Reference 3) Vincent and Tipton (1988) (Reference 68) showed that the maximum voluntary grip strength (MVGS) of subjects who immersed their unprotected hands or forearms in 5ºC water was reduced by 16% and 13% respectively, and that wearing a glove significantly reduced the MVGS by 16% in air and with the hand glove and water immersion combination, the reduction was 31%. Research has also shown that hand grip strength was reduced by up to 60% (Reference 7, 8, 20, 29), manual dexterity was reduced by 30% (Reference 11, 37, 56) and speed of finger flexion was decreased by 15-25%.

The Fire aboard the Hudson Transport on Christmas Day 1981 in the freezing water off the Gulf of St. Lawrence is a classic example where cold extremities contributed to the death of five seamen.

The raft was overcrowded. The night was pitch black. The deck lights had gone out a short time before. They could hear air escaping. They could feel freezing water coming up around them. A spirit of sauve qui peut seized them all. Six men made it back to the deck. They were helped by the captain and Kennedy to scramble up the ship’s side…. Their desperate plight may be imagined from the fact that some of them were so chilled by wind and water that they climbed the ladder using knees and elbows rather than hands and feet. Five others… fell into the sea and were lost. Perhaps some of them were simply too cold to be able to climb up the ladder….

(Quotation from The Hudson Transport Report of Formal Investigation No. 109. ISBN 0-660-51972-0)

Death from cold shock is not uncommon. These are typical examples that are regularly reported in the Canadian press each year.

There are several common threads in these accidents:

•  the victims were good swimmers

•  the water was cold

•  death occurred within a matter of only minutes - much too early for hypothermia to set in

•  they were all healthy people

•  they were all in shallow water

•  the accidents occurred within feet of the shore.

Most important, there was potential help at the scene of the accident, but no one recognized the danger of sudden death from cold shock in an otherwise healthy person.

This is the precise reason why standards for wearing lifejackets and / or carriage of liferafts must not be relaxed when operating in cold water. Carriage of EPIRBs (with their 90 minute to 2 hour response time), and the fact that the vessel may be operating in a group or close to shore is not a reason for a waiver.

The clear message is that sudden entry unprotected into cold water is very dangerous and should be avoided wherever possible. This applies to everyone whether commercial operators or recreational boaters.

It has now become apparent that much more emphasis must be put on swimming failure as a cause of death. It must also be understood that ability to swim in warm water is no indication of how well a human can swim in cold water. The classic testimony heard in the coroner’s court is: "We saw him go over the side, he started to swim and by the time we had the boat turned around and tried to identify where he was lost, he had disappeared. How could that be? He was an excellent swimmer."

These are not rare events either and are commonly reported in the newspaper.

Halifax Herald, June 18, 1996

Markle (1991) in his study of life-saving appliances (Reference 41) cites a classic example of swimming failure in 15°C water.

FISH-N-FOOL February, 1987

Tipton et al (1999) (Reference 63) studied the deterioration of swimming performance after the subjects had adapted to the stage one cold shock respiratory responses. All ten competent swimmers completed a 90-minute swim in 25ºC water; eight completed the swim in 18ºC water. In 10ºC water, five swimmers completed 90 minute swims, four were withdrawn between 22 and 50 minutes close to swim failure and one was withdrawn at 61 minutes close to swim failure. Stroke rate and length were similar in 25ºC and 18ºC water throughout the swims, but in 10ºC water the stroke rate was increased and the stroke length decreased. These changes were most pronounced in those close to swim fatigue. Stroke length decreased by 50% during the last 30 minutes for the swimmer who reached swim failure in 61 minutes.

Coincident to this, the average swimming angle increased from an average of 18º at the start of the swim to 24º at the end of the swim. The swimmer who reached swim failure finished with a swim angle of 35º. After 15-30 minutes in 10ºC water, swimmers’ fingers were splayed and started to flex. At the end of the swims, swimmers reported that it became increasingly difficult to straighten their limbs and coordinate swimming movements. Grip strength was not altered by swimming in water at 25ºC, but in water at 18ºC and 10ºC, it was significantly decreased by 11% and 26% respectively.

Wallingford et al (2000) (Reference 69) investigated the factors which limit cold water swimming distance while wearing a personal flotation device. Five female and twelve male subjects took part in a swim in 14ºC water. The subjects swam an average of 889 metres before swim failure. There was no correlation between distance swum and percentage body fat, aerobic fitness and abdominal skinfold thickness. However, those who swum the greatest distance had a significantly larger tricep skinfold thickness.

Wallingford et al. agreed with the conclusion made by Giesbreicht (1995) (Reference 12) that the majority of the decrement in arm performance is due to the local cooling of arm tissue and not due to hypothermia. Wallingford’s study did not support the assumption made by Hayward et al (1975) (Reference 23) that hypothermia could be responsible for the inability to swim in cold water while wearing a personal flotation device. If Hayward’s prediction was correct, the swimmers would have covered a distance of 2058 metres before incapacitation. This was more than double the distance of 889 metres covered by the subjects long before incapacitation from hypothermia (end average core temperature of 35.8ºC).

Tipton (1989) (Reference 59) had already documented the initial cardio-respiratory responses to immersion in cold water, i.e. the massive increase in heart rate and blood pressure within the first three minutes of immersion. Then in 1994, Tipton et al investigated the cardiac responses to submersion in water of 5ºC and 10ºC. (Reference 62). Ectopic arrhythmias (irregular heartbeats) were observed in 11 of the 12 subjects in 29 of the 36 submersions. These occurred immediately after breaking of breath hold, i.e. just at the time after jumping into the water and having to take a breath. They were benign in most cases, (i.e. they were of short duration, supraventricular in origin and producing no symptoms). However, this may not be the case for an aging population of tourists that may have to abandon a vessel in cold water, such as the St. Lawrence River or one of the Great Lakes. For those with a potential heart conduction defect, the heart is likely to be very susceptible to sudden immersion in water of 10ºC, resulting in a cardiac arrest or death. Sudden immersion in cold water to the neck makes the heart much more susceptible to arrythmias, due to an increase in output of the stress hormones (i.e. Adrenaline, Noradrenaline). The frequency of these arrhythmias is higher when the face is immersed.

In order to understand the cause of hypothermia, it is important to understand the basic physics of how a human maintains heat balance.

Heat flows down a thermal gradient from high to low temperatures. Thus, in the cold, a thermal gradient is established, down which heat "flows" from the warmer deeper tissues to the cooler tissues near the surface of the body. Heat then escapes from the body to the environment. In normal circumstances in air, the body can exchange heat with the environment via four physical processes: radiation (R), convection (C), conduction (K), and evaporation (E).

For body temperature to remain stable in a cool environment, the heat produced by the body at rest or through exercise or shivering (M), must match that lost by R,C,K and E.

Several factors influence the amount of heat exchanged by R,C,K, and E. The most common are: the surface area involved in heat exchange; the temperature gradient between the body and the environment; and the relative movement of the fluid (air or water) in which the body is placed. This explains why someone will cool faster if: they are in colder water (gradient); they are partially immersed compared to completely immersed (surface area); they are in fast flowing as opposed to still water (movement of the fluid); they move about compared to staying still (relative movement of the fluid).

In water, heat is conducted to the molecules of water in contact with the skin ("boundary layer"), these molecules are warmed and rise (Convection), and are replaced by cooler ones. Thus, in water only two of the four primary pathways for heat exchange are available, and heat loss is principally by convective and conductive heat exchange. Despite this, a naked individual in cold water will cool approximately four times faster than in air at the same temperature. This is because the thermal conductivity of water is 25 times that of air, and its volume-specific heat capacity is approximately 3500 times that of air. Therefore, water has a much greater capacity to extract heat (see Footnote). Furthermore, when in water, unlike air, the surface area available for heat exchange with the environment comes close to 100%. This is the reason why cold water is so dangerous. The corollary to this is that hot water is a very good medium to rewarm hypothermic victims.

If the immersed person has survived the initial two stages of immersion, i.e. cold shock and swimming failure, then the next hurdle to face is hypothermia. It is now known that this per se may not be the cause of death. This was noted by Golden (1996) (Reference 19). As previously stated in Chapter 1, the predicted 50% survival times for fully clothed men in water wearing lifejackets are 1 hour at 5°C, 2 hours at 10°C, and 6 hours at 15°C. Yet these figures are difficult to validate in the laboratory where the body temperature only falls about two or three degrees in the equivalent time. There must be another cause of death. Golden explained that a conscious survivor in a seaway will make the physical effort to keep his/her back against the waves, but when physically impaired through muscle cooling, semi-conscious and with a loss of determined will to survive, both of which occur after a body core temperature drop between 2-3°C, then the survivor turns into the waves and drowns. He also emphasized the point that death will occur much quicker from drowning if a lifejacket is not worn (Figure 5, Reference 15).

Footnote: The volume-specific heat capacity is obtained by multiplying the specific heat of a substance by its density. It represents the amount of heat required to raise the temperature of a given volume of water by 1ºK. At 37ºC the volume-specific heat capacity of water is 3431 times that of air.

Swimming has a massive impact on the rate of body cooling and can increase the rate between 30-40% (Reference 35).

In spite of good teaching programs and regulations for lifejackets, people still die of hypothermia. The latest survival prediction curve comparison as previously mentioned, is presented by Oakley and Pethybridge in 1997 (Reference 50).

Markle provides several classic examples of death from hypothermia in water below 15ºC in his report. Again, from Markle’s report (1991) (Reference 41).

JOAN LA RIE lll October, 1982

The argument that liferafts are not necessary because vessels operating near shore in day time can expect other vessels to come to the rescue quickly is not supported, nor is the addition of an EPIRB going to speed up rescue to this type of response time. As already stated, death will occur within 3-5 minutes for those who have not donned a life jacket, or from swimming failure within 30 minutes if not clothed properly and supported by a lifejacket. Markle’s (1991) (Reference 41) review of US lifesaving systems for small passenger vessels from 1973 – 1990 came to precisely the same conclusion.

Markle further correctly noted that persons in the water with and without lifesaving equipment died at a much higher rate than predicted by the estimated survival graph. This supports Golden’s theory that many victims drown during the cold shock and swimming failure stage of immersion, not from hypothermia per se. Even if they survive long enough to cool, cold-induced muscle incapacitation can prevent their keeping their backs to the waves, and thus their oro-nasal cavities clear of water, sometime after their body core temperature is reduced 2-3ºC.

Markle further concluded that "The present requirements for lifejackets, life floats and buoyant apparatus have proven adequate in all studied casualties where water temperature was 15ºC or more". This might have been the case in this study, but it is still possible to die from hypothermia and post rescue collapse as in the case of the Lakonia in 1965 that sank in 17.9ºC water off Madeira (Reference 34).

The provision of a buoyant apparatus in which the survivor is basically floating with head only out of the water clinging to a becketed line in water below 15ºC is only a last ditch measure if everything else has failed. Drowning is very likely from cold shock and swimming failure, in the short term, and hypothermia and post rescue collapse in the long term. The colder the water, the greater the chance of death. Again, as Markle clearly pointed out, in the case of the Cougar accident, the two people who managed to get themselves on top of a buoyant apparatus were the two not to be hospitalized. The remainder had to remain clinging to it in water at 13ºC, three died. Similarly, in another case referred to by Markle (Zephyr ll accident), if the device had been a liferaft instead of a buoyant apparatus, the person without the lifejacket would have been able to board it and would have survived the few minutes in the water. In this accident, eight of the survivors got separated from the boat. They decided to swim to an island, only one was alive six hours later when he called for help when almost ashore.

The Ocean Ranger sank in near freezing water on the Grand Banks off Newfoundland in February 1982 with the loss of all 84 men. No one was outfitted with a survival suit, although some wore lifejackets. The cause of death was attributed to drowning from hypothermia, yet from the testimony available, many died after only a matter of a few minutes in the water.

Quotation from the National Transportation Board Marine Accident Investigation Report NTSB-Mar-83-2, testimony from the Master of the Seaforth Highlander:

Death obviously in this case was caused by cold shock and possibly swimming failure, but certainly not hypothermia.

This question was raised after several rapid sinkings occurred. Particular accidents cited have been the loss of the MV George Prince (1976) (Reference 65) in the Mississippi River where 76 people died, the loss of the USCGC Cuyahoga (1978) (Reference 66) in Chesapeake Bay where 11 people died; the loss of the Marchioness (1989) (Reference 40) in the River Thames, UK, where 51 people died; and the loss of the MV Miss Majestic (1999) (Reference 67) on Lake Hamilton, Arkansas where 13 people died. The problem in each of these accidents was that many of the people were trapped between decks. The wearing of an inherently buoyant lifejacket would have further hampered their escape if it was possible. Nevertheless, for those who found themselves in the water and in the dark in two of the accidents, a lifejacket was critical to their survival.

If one is therefore going to regulate that passengers must wear a lifejacket on a passenger-carrying vessel that does not have the ability to carry a liferaft, then the lifejacket must be an inflatable one. The modern inflatable lifejacket is an excellent piece of life-saving equipment; it is comfortable, unobtrusive and very reliable. The Europeans have been using them for recreation and commercial boating operations on their lakes, rivers and canals for years. Canada has simply been slow in effecting new legislation for approval and it is only in the last five years that they have started to come into general use.

The argument from ship’s operators that they are expensive to purchase and maintain is only partially true. The fact is that once operators start to use them and passengers become familiar with them, then the confidence in their merit will go up, the price (due to a higher demand) will go down, and maintenance costs will correspondingly go down due to the general public starting to respect a very good piece of equipment that will potentially save their life. The two children in the True North II accident would have likely been alive and well today if they had worn a good inflatable lifejacket as they stepped on board the boat.

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