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BPK 142 > 11. Environmental Physiology: Cold and Underwater > Flashcards

11. Environmental Physiology: Cold and Underwater Flashcards

1
Q

What are homeotherms?

A

Homeotherms are organisms, like mammals and birds, that can maintain a stable internal body temperature regardless of external conditions, enabling them to function effectively in various environments.
– Resting Tc is 36.5 - 37.5oC.

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2
Q

What is the core defined as?

A

The core is defined as the temperature of the hypothalamus, which is the site of temperature regulation.

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3
Q

How is the temperature of the
core measured?

A

Experimentally the temperature of the core is measured using
– rectal and esophageal probes
– pills that are swallowed and send a temperature signal from the GI tract

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4
Q

How is Skin temperature measured?
How is Skin Temperature Influenced?

A
  • Skin temperature is measured with dermal patches.
  • Skin temperature is influenced by the environment, metabolic rate, clothing and hydration state
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5
Q

What is Hypothermia?

A

Hypothermia: Tc is below 35oC

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6
Q

What is Heat exhaustion?

A

Heat exhaustion: Tc 38.5 - 40oC

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7
Q

What is Heat stroke?

A

Heat stroke: Tc 40oC

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8
Q

What can The body can gain heat through?
(4)

A
  • Basal metabolic rate
  • Muscle activity
  • Thermic effect of food
  • Shivering
  • Environment
  • Radiation
  • Conduction
  • Convection
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9
Q

What is Resting Core Temperature?

A

36.5 - 37.5 (degrees Celsius)

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10
Q

Mechanisms of Heat Loss (4)
(ON EXAM)

A
  1. Radiation
  2. Conduction
  3. Convection
  4. Evaporation
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11
Q

What is Radiation?

A
  • the exchange of electromagnetic energy waves emitted from one object and absorbed by another.
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12
Q

What is Conduction?

A

occurs whenever two surfaces with differing temperatures are in direct contact.

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13
Q

What are Insulators?

A

Insulators - do not conduct heat easily.

  • Still air is an excellent insulator,
  • while water is an excellent conductor.
  • Heat conduction in water is about 25 times greater than in air.
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14
Q

What is Convection?

A
  • Requires that one of the media be moving as occurs with a fluid or gaseous medium.
  • For example, heat transfer from skin to moving air or water.
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15
Q

What is the Wind Chill Index?

A

Wind Chill Index
- gives the equivalent still air temperature for a particular ambient temperature at different wind velocities.

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16
Q

What is convective heat loss determined by?

A

temp gradient between skin, air, and air/water velocity

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17
Q

What is Evaporation?

A

The transfer of heat from the body surface through the change of liquid water on the skin to a gaseous water vapour in the environment.

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18
Q

What are the two primary physiological responses used by humans to defend against a cold environment?

A
  1. Increase in metabolic rate
  2. Increased tissue insulation
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19
Q

What are 2 ways to increase metabolic rate?

A

Increase in metabolic rate
a) voluntary - exercise - can increase heat production by 10-20 times the basal rate

b) involuntary - shivering - can increase basal rate 3-4 times

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20
Q

What is Increased tissue insulation?

A

Increased tissue insulation refers to the physiological or external measures that enhance the body’s ability to retain heat, helping to keep it warm by reducing heat loss to the environment.

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21
Q

Air vs Water

A

water takes away heat from 25x faster than air

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22
Q

The head and heat loss

A

Because the superficial blood vessels in the head do not constrict in the cold, the head is an important source of heat loss - accounts for 30 - 35% of total heat loss at rest.

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23
Q

Factors Affecting Responses to Cold (3)

A

A. Skinfold Thickness
B. Gender
C. Clothing

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24
Q

Skinfold Thickness

A

The thicker the fat layer, the greater the insulation.

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25
Q

Factors Affecting Responses to Cold
B. Gender

A
  • The average female has more subcutaneous fat than the average male -> more insulation
  • However, women generally have larger surface area to mass ratios than men. Children have even higher surface area-to-mass ratios.
  • When men and women with similar skinfold thicknesses are compared, women lose heat more rapidly than men during immersion in cold water.
26
Q

Factors Affecting Responses to Cold
C. Clothing

A
  • The effective insulation afforded by clothing is a function of the air layer next to the skin, the thickness of the clothing, and the air trapped between the layers of clothing.
  • More clothing insulation is needed during rest than during exercise.
  • Clothing insulation is reduced if the clothing becomes wet.
27
Q

Dry suit vs Wet suit

A

Wet suit for water,
Dry suit vs cold water

28
Q

Clothing in cold weather

A

Multiple layers of clothing are advisable during exercise in cold weather.
The outer layer should be water-repellent and wind resistant. Middle layers should provide insulation

29
Q

Keys for Clothing

A
  • The innermost clothing layer should not only provide insulation but also wick moisture away from the skin
  • This reduces evaporative heat loss.
  • Polyester or polypropylene thermal underwear work well, while natural, Merino wool still works best.
  • Clothing insulation is reduced if wind penetrates the outer garments. (outer layer should be wind resistant)
30
Q

Most responsible for heat loss at room temp

A

radiation

31
Q

Cold Injuries (3)

A

A. Hypothermia
B. Frostbite
C. Cold Exposure and the Respiratory Tract

32
Q

What is Hypothermia? (5)

A
  • A condition characterized by a body core temperature below 35oC.
  • Critical areas for heat loss - head, neck, sides of chest, groin
  • Shivering will cease when core temperature (Tc) falls below 32-34oC.
  • Death occurs when Tc drops to 24-28oC.
33
Q

Factors associated with hypothermia (7)

A
  1. Immersion in cold water or wet clothing
  2. Wind
  3. Physical exhaustion
  4. Inadequate clothing for conditions
  5. Low percent body fat
  6. Hypoglycemia
  7. Alcohol consumption
    - causes a decrease in shivering, increased blood flow to skin, impairs judgment
34
Q

oxyhemoglobin during hypothermia

A

Hypothermia causes the oxyhemoglobin dissociation curve to shift to the left

35
Q

Warning Signs of Hypothermia

A
36
Q

Why does hypothermia cause the oxyhemoglobin dissociation curve to shift left? What occurs to the tissues and the rest of the body?

A

1) increased hemoglobin affinity for O2
2) less O2 is released in tissues
3) tissues shift to anaerobic metabolism
4) Hypoxia of hear and brain plus metabolic acidosis
5) Depressed brain function and cardiac output
6) Ventricular fibrillation and death

37
Q

What is Frostbite?

A

Freezing of superficial tissues which occurs when skin temperature reaches between -2 to -6 degrees C.

Many people are unaware of frostbite because the sensory nerves are blocked and the skin is numb

38
Q

Cold Exposure and the Respiratory Tract

A
  • Inhaled air is conditioned as it enters the upper respiratory passageways - warmed to 37oC and saturated with water vapor.
  • Therefore you can’t “freeze” your lungs when exercising in very cold weather.
  • Since cold air is very dry, cells lining the respiratory passageways become dry, possibility of throat irritation.
39
Q

Effects of Cold on Performance

A

A. Strength, Power & Flexibility
B. Cardiovascular Endurance

40
Q

Decrease in _____ when muscle and nerve temp decrease

A

– strength and power
– nerve conduction velocity
– reaction time
– manual dexterity
– flexibility

41
Q

Effects of Cold on Performance
B. Cardiovascular Endurance

A
  • Optimal marathon race performance occurs at 14 degrees Celsius. This is because more of the circulation can be directed to working muscle, as less is required for heat dissipation.
42
Q

Cold-water immersion

A
  • Cold-water immersion can result in much more dramatic and rapid heat loss
  • Water is 25 times more conductive than air.
  • Survival for more than a few hours is unlikely even in water that is 10 degrees Celsius, like the Georgia Strait.
43
Q

Pressure Effects

A

Pressure of air at sea level =
one atmosphere or 760 mm Hg

The pressure increases by one atmosphere for each additional 10 m (33 ft.) of depth. in water
10m (33 ft.) = 2.0 atmosphere
20m (66 ft.) = 3.0 atmosphere

Because the tissues of the body are mostly water, they are non-compressible.

44
Q

Snorkle Size Limit

A

Snorkelling
* There are limits to snorkel size because of :
1. Pressure effects
2. Increase in pulmonary dead space

45
Q

Pressure Effects on Snorkelling

A

Pressure effects
– when breathing through a snorkel, the diver must inspire air at atmospheric pressure.

– At a depth of only 3 ft., the compressive force of water against the chest cavity is so large that the inspiratory muscles are usually
unable to overcome external pressure and expand the thoracic cavity.

Sea water = 64 lbs per cubic foot
Fresh water = 62.5 lbs per cubic foot

46
Q

Increase in pulmonary dead space

A

Normal anatomical dead space = 150 ml.
Dead space of regular snorkel = 150 ml.

As snorkel size increases, VD increases. You will need to work harder, at a higher VT, in
order to maintain VA

47
Q

Breath Hold Diving

A
  • As the skin diver descends, the air in the lungs is compressed -> lung squeeze.
  • When lung volume is compressed below residual volume -> lung damage occurs as blood is sucked from the pulmonary capillaries into the alveoli
  • “Normal” maximal breath holding time after a maximal inspiration of ambient air is approximately 50 - 60 seconds.
  • The arterial PO2 then drops to about 60 mm Hg and the arterial PCO2 rises to 50 mm Hg.
48
Q

What is Paradoxical drowning?

A

Paradoxical drowning - Diver hyperventilates, holds breath, and dives down to a certain depth

  1. gases in the lung are compressed and partial pressures are increased
  2. diver holds breath as long as possible and then starts to ascend
  3. partial pressure of gases in lung decrease on ascent
  4. PaO2 decreases below critical point
  5. diver loses consciousness and drowns.
49
Q

What is Scuba?

A

Scuba – self-contained underwater breathing apparatus

50
Q

Equipment needed for scuba diving

A
  • mask and snorkel
  • clothing - wetsuit or dry suit, gloves, hood, fins, boots
  • weight belt
  • buoyancy compensator
  • tank and backpack
  • depth gauge and pressure gauge
  • single hose, two-stage regulator
51
Q

What are The two regulators for?

A

The two regulators reduce the air pressure in the tank by approx. 2500 psi (when tank is full) to exactly the ambient water pressure at the diver’s mouth, allowing ease of breathing.

Underwater breathing systems must supply air at sufficient pressure to overcome the force of water against the diver’s chest.

52
Q

Open-circuit scuba

A

Open-circuit scuba - used by sport divers - as the diver starts to inspire, the slight negative
pressure causes the inspiratory valve on demand regulator to open ! air enters diver’s
lungs. On exhalation, the exhaled air is discharged into the water.

53
Q

Potential Medical Problems Associated With
Scuba Diving (7)

A
  1. Air Embolism
  2. Pneumothorax Lung Collapse
  3. Nitrogen Narcosis
  4. The Bends
  5. Oxygen Poisoning
  6. Mask Squeeze
  7. Middle Ear Squeeze
54
Q
  1. Air Embolism
A

Embolus - any material that enters and obstructs a blood vessel.

Rule - never hold your breath while scuba diving

55
Q
  1. Pneumothorax: Lung Collapse
A

Air pocket forms outside lungs between the chest wall and lung tissue, continued expansion of this trapped air during ascent causes lung to collapse

56
Q
  1. Nitrogen Narcosis
A

At depths of over 100 ft the increased partial pressure and amount of dissolved nitrogen produces an anesthetic effect on CNS (effects similar to alcohol intoxication)

57
Q
  1. The Bends
A

Also called “decompression sickness”.

When diver goes to surface too quickly after a deep dive the dissolved nitrogen moves out of solution and forms bubbles in body tissues and fluids

58
Q

The Bends Treatment and Prevention

A

Treatment: recompression in a hyperbaric chamber to force the nitrogen gas back into the solution and then slow decompression

Prevention: - ascend to the surface in stages - decompression stops to allow sufficient time for nitrogen to diffuse from the tissues to the blood without bubbles forming.

59
Q
  1. Oxygen Poisoning
A

Occurs when the inspired PO2 exceeds 1520 mm Hg for longer than 30-60 minutes

Effects: - irritation of respiratory passages which progresses to pneumonia if exposure continues
- muscle twitching
- confusion, nausea
- convulsions

60
Q
  1. Mask Squeeze
A

Mask should cover nose and eyes so pressure can be equalized (otherwise a relative vacuum is created)

Eyes can Bulge out of sockets

61
Q
  1. Middle Ear Squeeze
A

Relative vacuum is created in the middle ear, hemorrhage of tissues in the middle ear and possible rupture of eardrum

BPK 142 (18 decks)

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