Exhaustion, protective clothing and hypothermia

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Exhaustion, protective clothing and hypothermia

• Dr Charles McGurk
• http//staff.stir.ac.uk/charles.mcgurk/diving.htm
• cm26_at_stir.ac.uk
• Pathfoot office F22

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Lecture overview

• Thermoregulation
• Hypothermia
• causes
• prevention
• signs
• treatment
• Protective clothing
• wet suits
• dry suits
• Exhaustion
• prevention
• treatment

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Temperature regulation

• Mammals birds are homeothermic reflexes
  primarily integrated by hypothalamus maintain
  core body temperature within a narrow range
• Heat produced by muscular exercise, assimilation
  of food all vital processes contributing to
  basal metabolic rate
• Heat loss radiation, conduction convection
• Circadian fluctuation of 0.5 - 0.7C
• Different parts of the body are at contrasting
  temperatures

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reproduced from Ganong (1987) Review of Medical
Physiology, Appleton Lange, 665 pp.
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Hypothermia

• Depression of core body temperature below 35C
  (95F)
• Core torso, including vital organs
• Does not include chilled extremities
• Normal core body temperature 37C
• Decrease of 1C leads to shivering discomfort

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Scottish diving risk of hypothermia

• Seawater 4 - 16C freshwater gt 0C
• While submerged water conducts heat 25x faster
  than air
• On surface wind chill exposed to air as well as
  water, evaporation very effective at cooling
• Heat loss is related to surface area vs. body
  weight
• Activity produces heat - but uses energy and air

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Physiology

• 37C normal body temp
• 36C feeling cold, shivering, rise in metabolic
  respiratory rates, numbness, piloerection
• 35C uncontrolled shivering, metabolic
  respiratory rates starts to decrease
• 34C respiration, heart rate and blood pressure
  fall, causing confusion, lethargy, and
  behavioural changes
• 33C shivering stops, muscles become rigid,
  amnesia begins, mental confusion,
  semi-consciousness
• 28C lower limit for spontaneous recovery,
  respiration ceases, unconscious, pupil dilation,
  ventricular fibrillation
• 25C potentially fatal

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Be vigilant!

• Very important for every diver to be aware of
  hypothermia - in you and your buddy
• Communicate - tell buddy if you are cold
• It is critical that you dont become ineffective
  for personal and buddys safety
• Getting too cold leads to reduced rationality and
  mental awareness

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Symptoms clinical signs

• In ascending order of severity -
• Complaint of cold - feeling cold
• Shivering (controllable), goose pimples
• Uncontrollable shivering
• Neurological symptoms (behaviour, lethargy)
• Cessation of shivering
• Visual disturbance
• Collapse and unconsciousness
• Death

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Take action

• If buddy shows neurological signs
• The victim will probably not be aware of the
  developing problem - always be alert for the
  symptoms clinical signs in each other
• Always be prepared to cut the dive short if
  shivering develops

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Risky times for hypothermia

• Before a dive on shore or boat
• During a dive
• During the surface swim
• Between dives
• After dives - whilst changing
• On the way home

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Treatment of a hypothermic diver

• Remove wind / water chill factor
• Wrap in space blanket
• Lie patient down, raise legs, keep still
• Emergency treatment (e.g. CPR)
• In severe circumstances seek medical help
• Start with lots of warm dry clothing
• Warm (not hot) sweet drinks, no alcohol
• Prevention is better than cure!

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Protective clothing

• protection from
• cold abrasion
• pollution hazardous creatures

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Protective clothing

• Wet suits - normal
• - semi-dry
• Dry suits - membrane
• - neoprene
• - expanded
• - crushed
• Hoods, gloves boots

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Wet suits

• Made from neoprene
• Trap layer of warm water
• Warm when in the water and active
• Good fit is important
• Usually no boots attached
• Extra weight required
• Can get very cold while changing
• Of varying thickness

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Dry suits - membrane

• Allow extra layers to be worn underneath
• Water prevented from entering the suit by rubber
  seals (neck and wrist)
• Boots attached
• Hood required
• Inflated by direct feed
• Shoulder or cuff dump
• Less weight needed
• Can be very flexible

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Dry suits - neoprene

• Usually crushed, reducing air bubbles in material
  shrinking
• Thermally insulating
• Can be restrictive in movement
• Under suits can be worn
• Zip entry on back or front
• Inflated by direct feed
• Boots attached
• Usually about 5mm thick
• Prevents water entry by rubber seals around wrist
  and neck
• Buoyant extra weight required

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Wet suits vs. Dry suits

• A dry suit keeps you dry and a wet suit doesnt!
• Dry suits require inflation at depth and dumping
  of air during ascent
• Floaty feet can also be a problem
• Between dives a dry suit will keep you much
  warmer than a wet suit
• Dry suits are much more expensive than wet suits

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Exhaustion

• Easy to recognise - unable to respond to demands
• Must be avoided
• Signs
• deep laboured breathing
• mental and physical slowness and incomprehension

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Exhaustion causes

• Physical exertion
• Hypothermia
• Mental fatigue or stress
• Deep diving decompression diving

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Exhaustion avoidance

• Physical fitness
• Postpone diving if tired, stressed or unwell
• Fin at a comfortable pace
• Always go at the speed of the slowest
• Communicate with buddy if you cant keep up

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Exhaustion treatment

• Closely monitor a diver who is suspected of being
  exhausted end dive if necessary
• Shock and hypothermia can result, so treat
  accordingly
• Help diver tow, carry kit etc.
• Sweet, warm, non-alcoholic drinks
• Best not to dive for rest of day

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Summary

• Wear suitable well-fitting protective clothing
• Minimise exertion whilst diving
• Maintain reasonable level of fitness
• Do not dive if feeling tired, cold or unwell
• Signal to buddy immediately if cold or fatigued
• Take extra care at depth
• Enjoy your diving!