IMMERSION AND HYPOTHERMIA

January 1st, 2004 by JCB
Posted in Articles, Features, Technical and Training | No Comments »

Although this is a very grim topic to feature in the magazine the reality is that as pilots we daily face the risk of immersion frequently in conditions of extreme cold. The following article has been written by retired Liverpool Pilot Don Twells who has been a senior instructor with the British Red Cross specialising in Immersion and Hypothermia. Don has sent this for publication because he feels that pilots and pilot boat crews should be aware of the latest information on the subject. As one who hasn’t attended a First Aid course for many years my own recollection of dealing with immersion and hypothermia is not only very hazy but also well out of date. The explanations and techniques, especially those learned following the Fastnet disaster, could well save a life should the “unthinkable” happen.

DROWNING

Some 500 deaths per year occur from drowning in England and Wales alone. Approximately 19% occur in the sea, 71% in inland waters and swimming pools and a further 10% drown in their own baths. Many of the victims are competent swimmers and die within 1 metre of safety. Among adults, alcohol is a contributory factor.

PHYSIOLOGY OF DROWNING

Sudden immersion in cold water causes a sharp intake of breath resulting in panic breathing and frequent submersion. This compounds the respiratory distress and the victim, having compromised their buoyancy, may begin to sink, at the same time swallowing (not inhaling) large volumes of water. Water does not enter the lungs, it is prevented from so doing by a combination of repeat swallowing and laryngeal spasm eventually resulting in hypoxia, loss of consciousness and ultimately death. Water usually only enters the lungs at the point of death when the larynx becomes relaxed.

TYPES OF DROWNING

Near Drowning – The casualty is rescued just before the point of death. Dry Drowning – As the drowning person sinks and unconsciousness deepens they continue to try and breathe thus water flows through the pharynx stimulating the reflex which triggers the larynx and epiglottis to close off and protect the trachea, diverting water into the stomach. Due to acute hypoxia the casualty will have died before water enters the lungs. Fresh Water Drowning – If a sufficient volume of water enters the lungs it will cause an interference with the process of external respiration by preventing the passage of gases between the alveoli and the pulmonary capillaries. Haemodilution is created by the rapid absorption of the water into the blood which in turn grossly distorts the pH value of the blood. This may result in cardiac arrest some 2-4 minutes after rescue. Salt Water Drowning – In these circumstances the opposite occurs. Salt water entering the lungs is more solute than blood; therefore water is drawn into the alveoli from the blood stream increasing the volume of fluid in the lungs. This increases the viscosity of the blood and more sluggish circulation eventually slows the heart rate to the point where cardiac arrest occurs. This can occur 8-10 minutes after rescue. Types of protective clothing should include a face piece to prevent salt water splashing on the lips. Secondary drowning – Should a drowning victim be successfully rescued and resuscitated they may appear to have fully recovered. However, if water has entered the body, this can cause irritation to the pulmonary lining of the lungs which in turn leads to a clear secretion filling the lungs. death can occur up to 72 hours later.

MAMMALIAN DIVING REFLEX

Another feature of some drowning mainly in the young is the mammalian diving reflex. This primitive and little understood reflex is activated in circumstances where the victim is suddenly plunged into very cold water face first. The most immediate effect is the almost total shutdown of the respiratory, circulatory and nervous systems to the point of suspended animation and apparent death. Victims have been known to make a complete recovery after 38 minutes submerged and 16 hours resuscitation. It must be understood that a casualty when first immersed in cold water will behave very oddly. They may refuse rescue and indicate that they are swimming to the USA etc. They often will swim away from a boat or other means of rescue.

FIRST AID TREATMENT FOR DROWNING

• Establish Airway.
• If required commence resuscitation.
• Never perform abdominal thrust. (This will transfer water from stomach to lungs)
• Check pulse twice in different places. (Particularly if hypothermia is present).
• Never apply direct heat to a hypothermic victim.
• If a thermal blanket or exposure bag is available, remove wet clothing and place casualty inside.
NEVER GIVE UP ON A DROWNING PERSON – resuscitation should be continued until hospitalisation.

IMMERSION AND DROWNING

Immersion injuries and drowning are medical conditions which can affect a person who, deliberately or accidentally, goes into the water. They account for most deaths in water and for many of those occurring after rescue. Immersion injuries are due to the physical characteristics of water and its effects on the human body. The important characteristics of water are density, thermal capacity and thermal conductivity. These three together govern how immersion affects our heart, circulation and metabolism. If we remove heat loss from the equation and put a man into a swimming pool containing water at body temperature 37.C he will neither gain nor lose heat. Before entering the water much of his 5 litres of blood volume will have collected in the veins in his legs due to gravity. The water’s density is approximately the same as that of the swimmer’s body. In water he is weightless and the hydrostatic effect of water around the legs pushes the blood pooled in his veins back into the trunk, especially, the heart. The more blood the heart contains, the greater the cardiac output. The relationship between heart volume and cardiac output provides the reason for laying people down who have fainted or are in shock. This drains the blood from the veins in the legs and back to the heart thus increasing cardiac output. The increase in the return of venous blood from the legs to the heart during immersion also causes the hydrostatic pressure in the heart chambers and major blood vessels to increase. Effectively there is now too much blood in the heart. On land about 1 litre of blood was not being used, it had collected in the legs. When the swimmer is in the water the blood returns to the heart. The heart senses this surplus and gets rid of it by the increase of urine production in the kidneys. This process continues until cardiac output and pressures in the circulation return to normal. If the swimmer remains in the water long enough to lose a large amount of urine, when removed from the water the total blood volume will be much lower than before immersion. On standing up blood will again pool in the legs. Suddenly blood volume in the heart will be drastically reduced. Blood pressure and cardiac output will be reduced and blood flow to the vital organs will also decrease. The effects of immersion are increased still more if the water is cold. Water conducts heat 25 times more efficiently than air and can hold 1000 times without proper insulation, is therefore very rapid. The body responds to heat loss by constricting blood vessels, diverting blood away from the limbs and back to the trunk. The constriction of veins in the limbs exaggerates the effect of immersion on limb venous blood return and hence cardiac output, blood pressure and urine production. Cold also causes restriction of the blood vessels which carry blood away from the heart. When these arteries are constricted the heart has to work harder to overcome the increased resistance to flow. As a result the heart needs a greater oxygen supply because it is doing more work. If the heart does not receive this oxygen it can fail or stop completely. This is why cardiac deaths and other heart problems are much more common in winter than in summer. Both immersion and cold reduce the amount of blood in the limbs particularly the legs and increase the volume in the trunk. When the casualty is rescued, blood pools in the legs and causes blood pressure and cardiac output to fall below normal. This is the reason why during the Fastnet Race a few years ago so many persons died. Some stayed with their damaged yachts and they survived. Those that went into the water died, in most cases the casualties were alive when the helicopter arrived. They were able to talk and assist the winchman to put the lifting harness on. However as soon as they were lifted clear of the water, blood drained back to their dangling legs. Casualties went into shock, dying before they could be hauled into the helicopter. Rescue Helicopters now use horizontal stretchers and lift all casualties from the water in a horizontal stretcher and keep them horizontal until hospitalisation. The lesson to be learned from this is that even after swimming for pleasure never come out of the water and start running around or playing games. Instead sit quietly and allow the blood volume to readjust. 30 minutes should be sufficient.

FIRST AID TREATMENT OF IMMERSION

Whether an immersion victim lives or dies more often than not depends upon the first aid given by his rescuers, rather than the intensive care he receives subsequently after hospitalisation. For this reason it is essential that all those who may be engaged in the rescue of such victims should be absolutely clear on the correct first aid treatment to administer. In recent years medical research has identified several factors which may result in death, either during immersion or just after rescue. An understanding of these may assist the doctor in the medical management of the post immersion patient. In practice: 1. Is the casualty breathing, and is there a pulse present in a large artery (Carotid)? If not, clear the airway and begin Resuscitation. 2. Having ensured that adequate ventilation and heart action are present, try to prevent further heat loss by the use of windproof garments or blankets wrapped around the casualty. 3. Lift the casualty from the water in a horizontal position and keep the casualty in a horizontal position at all times and transport to the nearest medical care. NOTE In all first aid we do not now check for a pulse at the pressure points. Circulation or not is determined by observing the skin colour of face and lips.

HYPOTHERMIA

Hypothermia is the condition when heat is lost from the body core. Normal body temperature is 37ºC. Hypothermia occurs when the body temperature falls to 35ºC. If the body core temperature falls below 26ºC. then recovery is most unlikely and death is probable. The ability of the body to resist cold depends on age, health, fitness and psyche. Alcohol, some drugs and illness will all reduce the resistance to hypothermia. It is worth remembering that unusual behaviour may be evident i.e. a hypothermic person may complain of being too hot and will begin removing clothing. This must be discouraged.

SYMPTOMS – MILD HYPOTHERMIA

37ºC to 36ºC – Normal shivering has begun.
36ºC to 35ºC – Cold sensation, goose pimples, unable to perform complex tasks with hands, shivering can be mild to severe, hands are numb.

MODERATE HYPOTHERMIA

35ºC to 34ºC – Shivering is intense, muscle unco-ordination becomes apparent, movements are slow and laboured, stumbling pace is evident, mild confusion. Test by making the casualty walk for 30ft in a straight line. If unable to do so the casualty is hypothermic.
34ºC to 32ºC – Violent shivering persists, difficulty with speech, sluggish thinking, amnesia appears, gross muscle movements sluggish, unable to use hands, stumbles frequently and signs of depression.

SEVERE HYPOTHERMIA

32ºC to 30ºC – Shivering stops, exposed skin turns blue or puffy, muscle coordination very poor, inability to walk, confusion, incoherent irrational behaviour, but may be able to maintain posture and appearance of awareness. 30ºC to 27ºC – Muscle rigidity, semiconscious state, stupor, loss of awareness of others, pulse and respiratory rate decreases, possible heart fibrillation. 27ºC to 25ºC – Unconscious, heart and respiration erratic, pulse may not be detected. 25ºC to 24ºC – pulmonary oedema, cardiac and respiratory failure, death. Death may occur long before this temperature is reached.

FIRST AID TREATMENT:

Hypothermia The basic principles of re-warming are to conserve heat that they already have and to replace the body fuel they are burning up to generate that heat. If a person is shivering they have the ability to re-warm themselves at a rate of 2ºC per hour.
Mild to moderate Hypothermia Heat loss must be reduced by additional layers of clothing, increased physical activity and removing the person away from the elements. It is essential to keep a hypothermic person hydrated and fuelled. Carbohydrates will quickly be released into the blood stream for a sudden heat surge. These are the best to use for a quick energy intake especially in mild cases. Food intake should include hot liquids, sugars, proteins and fats but only in mild cases. Alcohol and tobacco (Nicotine) are to be avoided. Some external methods of providing heat should be carried out Body to body warming in a thermal blanket or similar.
Severe Hypothermia Heat loss must be reduced. Use of thermal blankets, bivvy bags, sleeping bags must be encouraged. In such insulated conditions casualties can re-warm themselves more efficiently than external warming. Food and fluids should not be given if hospitalisation is close by. However where the casualty occurs in isolation warm sugar water may be given. Note that the function of the stomach will have shut down and therefore solids should not be administered. This warm sugar solution may be given every 15 minutes. This will be absorbed directly into the blood stream, thus providing internal heat for the casualty.
• DO NOT RUB THE EXTREMITIES. (This will increase circulation and move the cold blood from the extremities to the vital organs)
• DO NOT GIVE ALCOHOL.
• DO NOT TRY TO HEAT THE EXTREMITIES ARTIFICIALLY. (This will also increase circulation)
• DO NOT PLACE THE CASUALTY’S LIMBS IN CONTACT WITH THEIR BODY.

Don Twells

Donald F. Twells 1934 – 2004

Died 15th June 2004

Don was born on 21^st March, 1934. He was educated at Prescott Grammar School and joined HMS Conway in September 1949 at the age of 15, where he was an excellent student and cross country runner. On leaving the ‘The Conway’ he sailed with Clan Line before joining the Liverpool Pilot Service in 1952 and served as an apprentice on the pilot vessels for 7 years. In 1959 Donald gained his 3^rd Class Licence and became 1^st Class in 1963. He worked as pilot until 1988, when the Government made changes to pilotage and he started a new job with the Mersey Docks & Harbour Co. in the VTS. During his time as a pilot he worked as a representative and as one of the small team organising social events.

Outside of pilotage, Donald will be particularly remembered for the 28 years work he did setting up and running the local Sea Scouts, where he passed on his knowledge of boat management and comradeship with enthusiasm and good humour. He became Assistant District Commissioner; was awarded a medal of merit for outstanding service and a silver acorn for especially distinguished service. Through his interest in first aid he became an expert on exposure recovery and hypothermia. Somehow, he also found time for his garden of which he was very proud, and which he opened to the public on occasions, and became the President of the local Horticultural Society.

Donald was a devoted family man and leaves behind his wife Norma and three sons. Donald will be truly missed and fondly remembered for the way in which he embraced life to the full.

Andy Malcolm,

Retired Liverpool Pilot