Challenging Environments Flashcards
(103 cards)
1
Q
What is pressure?
A
Pressure = force / area
2
Q
What is the pressure on a diver at the surface?
A
Atmosphere above diver (150Km) = atmospheric pressure
3
Q
What is ATA
A
Atmosphere absolute
The total ambient pressure on the system being calculated or measured
4
Q
What is 1 ATA?
A
1 ATA = 1 bar = 101.3 kPa = 1kg/cm2 =
760mmHg = 14.7 psi
5
Q
What is the water pressure above a diver?
A
Hydrostatic pressure
6
Q
Which is heavier water or air density?
A
Water
7
Q
What are the readings as you go further down in the water?
A
Sea level = 1ATA = 1 bar = 0 ATG
10m down = 2 ATA = 2 bars = 1ATG
20m down = 3 ATA = 3 bars = 2 ATG
8
Q
What are the 3 important factors of divers regarding pressure?
A
Gas volumes
Gas solubility
Temperature
9
Q
What is Boyle’s law?
A
Volume of a given amount of gas is inversely proportionate to pressure
P1 x V1 = P2 x V2
P x V = constant
10
Q
What is Boyle’s law important for?
A
Gas compression in cylinders
Descent/ascent problems
Buoyancy
11
Q
What is Charles’ law?
A
At a constant pressure, the volume of a given amount of gas varies directly with temperature
V (is proportional to) T
12
Q
How do you work out absolute temperature in Kelvin
A
K = 273 + Celsius
13
Q
Examples of Charles’ law
A
Heated gas expands
Cooled gas contracts
Affects tank pressures
14
Q
What is the general gas law?
A
Boyle’s and Charles’ laws combined:
P1V1/T1 = P2V2/T2
15
Q
What does general gas law result in?
A
Rapidly expanding gas cools
Rapidly compressing gas heats
16
Q
What is the air we breath in made of?
A
Mixture of:
- N2 = 78.6%
- O2 = 20.8%
- H2O = 0.5%
- CO2 = 0.04%
17
Q
What are the two ways to present the amount of each gas present in the atmosphere?
A
Percentages - out of 100%
Partial pressures - out of 760mmHg
18
Q
What is Dalton’s law?
A
In a gas mixture, total pressure exerted by the mixture is the Sun of the pressures that would be exerted by each gas if it alone occupied the total volume
Patm = PN2 + PO2 + PH2O + PCO2
19
Q
What is Henry’s law?
A
The quantity of gas which will dissolve in a liquid (at a given temp) is proportional to partial pressure of gas in contact with the liquid
20
Q
What does Henry’s law influence?
A
The amount of gas going into and out of solution - descending and ascending
21
Q
How do you work out density?
A
Density = mass / volume
22
Q
What is specific gravity (SG)?
A
The density of a substance compared to density of fresh water
23
Q
Which is denser fresh water or sea water
A
Sea water
Objects are also more buoyant in sea water
24
Q
What does water do to heat?
A
Water has a high capacity to conduct and absorb heat
25x greater than air
25
What happens during decompression disorders?
Increased depth = increased absolute pressure
Increased gas partial pressure gradients for 02, N2
Increased diffusion into pulmonary circulation till new equilibrium reached
Increased diffusion into tissues
26
What determines the rate at which equilibrium is reached while diving?
Tissues with high blood flow equilibrate quickly - heart, brain, kidneys, liver
Tissues with low blood flow equilibrate more slowly - ligaments, tendons, fat
27
If ambient pressure drops too quickly on ascent gas bubbles are formed, what is the known as?
The bends
28
What types of ‘bends’ are there?
Synovial joints (most common)
Skin bends - skin itching
Oedema - lymph vessel blockage
The staggers - inner ear disturbance
The chokes - bubble blockage of pulmonary circulation
Spinal bend - peripheral sensory / motor disorders
CNS bend - visual blurring, headache, confusion, paralysis and coma
29
What is a barotrauma?
It is caused by expansion/contraction of gases in existing air spaces
30
Where are common sites for barotrauma?
Middle ear
Sinuses
Teeth
Lungs
Mask
Diving suit
31
What is narcosis?
A reversible change in consciousness
32
What is narcosis caused by?
Inert gas - N2 or He most common
O2 toxicity
CO2 - much less common
33
What are the effects of narcosis and when is it like to occur?
Breathing at >30m
- Euphoria
- Excitement
- Mental impairment
- Confusion
- Hallucination
- Unconsciousness
34
What do we know about narcosis?
Related to gas solubility in lipids
Different gases display the same narcotic effects at same molar concentration in tissues
Increased solubility = decreased partial pressure for narcosis
He can replace N2 at dives greater than 40-50m
- less lipid soluble and less dense
CO2 is a powerful narcotic and can work in synergy with N2
35
What are the cardiovascular effect of immersion?
Head out immersion
Hydrostatic compression of tissues
Decrease venous activity
Increase ECF
Increased venous return
Increased cardiac volume
- Split -
1) activation of stretch receptors
1) release of ANO
1) decrease RNSA
1) decrease ADH
1) decrease renin / ADH
1) naturesis / diuresis
2) increased stroke volume / CO
2) increased BP, baro stimulation
2) decreased HR but increased TPR
2) normal BP
36
How far can you dive while holding your breath?
Ama divers - 20m
Pearl divers - 50m
Free divers - 172m
37
What is the breaking point determined by for holding your breath?
Arterial PCO2 not O2
>55mmHg
38
When is hypoxic unconsciousness reached?
When O2 < 25/30mmHg
39
What is the diving reflex? And what is it used for?
Fascial immersion
Slows the heart down
Diverts blood to heart, lungs and brain
40
What does the diving reflex trigger?
Apnoea
Intense bradycardia
Peripheral vasoconstriction
41
What normally happens when you hold your breath?
Voluntary signal from cortex
Respiratory centre inhibited
Breathing ceases
Little / no effect of cardiovascular control
Chemoreceptor stimulation eventually overrides breaking point
42
What happens during cold water immersion?
Voluntary signal from cortex and trigeminal nerve activation
Respiratory centre strongly inhibits respiratory muscles
Breathing ceases
Respiratory centre activates
- vagal PNS
- profound bradycardia
Sympathetic nerves cause peripheral vasconstriction
Chemoreceptor stimulation
- reinforces peripheral vasoconstriction
- now ineffective at causing break point
43
What happens due to pre dive hyperventilation?
Decrease in arterial PCO2
PO2 decreases to <25-30mmHg during dive
Hypoxic syncope before PCO2 drive breaking point
44
What happens during a deep water blackout?
Syncope can occur on ascent from depth
During dive hypoxia occurs, but PO2 > 25-30mmHg
On ascent hydrostatic pressure decreases
- PO2 decreases as a result
- PO2 abruptly <25-30mmHg
- Hypoxic syncope
45
What region of the brain acts as the body’s thermostat and regulates core body temperature?
Hypothalamus
46
Where are the receptors that detect heat changes?
Thermal core receptors
Thermal skin receptors
47
What part of the hypothalamus deals with excessive heat?
Anterior hypothalamus
48
What part of the hypothalamus deals with excessive cold?
Posterior hypothalamus
49
How is temperature reduced?
Vasodilation
Sweating
Reduced activity
Stretched body position
Decreased appetite
50
How is temperature raised?
Vasoconstriction
Shivering
Increased activity
Huddled position
Increased metabolism
51
What is the heat balance equation?
Heat storage = (metabolism - work) -
(Conduction + convection + evaporation + radiation)
Heat storage = production - loss
52
How is heat gained by the body?
Reactions of energy metabolism
- at rest : major organs
- during exercise : skeletal muscle
Absorption for the environment (radiation/conduction)
- when ambient temperature is greater than body temperature
53
How efficient is the body at retaining energy?
25% efficient
75% of energy is lost as heat
54
How is heat lost?
Radiation - electromagnetic radiation transferred to bodies not in contact
Conduction - movement of heat to bodies that are in contact
Convection - transfer of her to a moving gas or liquid
Evaporation - heat transferred to environment as water vaporised from respiratory passages and skin surface
55
What does total sweat vaporised from skin depend on?
Surface area exposed to environment
Temperature and relative humidity of ambient air
Convective air currents around the body
56
What is the most important factor regarding evaporative heat loss through sweat?
Relative humidity
57
What happens to the rate of evaporation when humidity increases?
The effect of evaporational cooling decreases
58
How does the body deal increases in core temp?
Circulatory
- cutaneous blood flow increases from 10% CO to 15-25% CO
- arterial and venous vessels dilate
- increase HR
Evaporation
Hormonal adjustments
- body conserves water (H2O) and salt (aldosterone)
59
What organ receives most of the CO during exercise in heat?
Exercising muscle
60
How is water loss effected when exercising in heat?
Water loss can be <3L/hr
61
How should you stay hydrated during exercise in heat?
Maintain plasma volume so that circulation and sweating can progress at optimal levels
62
What is the difference in sweat composition in a trained and untrained individual?
Untrained
- Na+ 90mmol/L
- Cl- 60mmol/L
- K+ 4mmol/L
Trained
- Na+ 35mmol/L
- Cl- 30mmol/L
-K+ 4mmol/L
63
What are the benefits of heat acclimatisation?
Thermal comfort increased
Improved exercise performance
64
How is thermal comfort improved by heat acclimatisation?
Decrease in core temperature
Sweating - earlier, more dilute, increased rate
Blood flow to skin earlier
Less body heat production
65
How is exercise performance improved by heat acclimatisation?
Decrease in heart rate
Effective distribution of CO
Thirst improved
Decreased Salt losses - sweat and urine
Decreased reliance on CHO catabolism
66
What factors modify heat tolerance?
Training (>50% aerobic capacity)
Pre-cooling
Body fat level
Medications (diuretics)
Clothes
Age
67
What happens during cold stress?
Vascular
- cutaneous vasoconstriction
- BF in cold <1mL/min/100g
Muscle activity
-shivering
-physical activity
-increased O2 consumption
Hormonal output
-catecholamines
-thyroxine
Insulators benefits of skin and subcutaneous fat
68
What are the results of acclimatisation to cold?
Shivering begins earlier due to increased NA
Increased thyroxine
Cold induced vasodilation
Improved ability to sleep
69
At what core temperature does severe hypothermia set in?
32.2 - 23.9 degrees Celsius
70
What are the signs and symptoms of severe hypothermia?
Muscle rigidity
Exposed skin blue and puffy
Inability to walk
Confusion decreased pulse and respiration rate
Possible heart fibrillation
Unconscious
Death
71
What are the fingers, toes, ears and nose at the greatest risk during cold?
They do not have major muscles to produce heat
Body conserves heat favouring internal organs
Have a high SA to volume ratio
More likely to be in contact with colder surfaces
72
Give two examples of non-freezing injuries
Chilblains - dry cold
Trench foot - wet cold
No permanent damage
73
Give two examples of freezing injuries
Frostbite - Ice forms within cells, cells rupture leading to cell death
Deep frostbite - all muscles, tendons, blood vessels and nerves of affected extremity are frozen
74
How do you work out the partial pressure of O2 at sea level and at Mount Everest?
Sea level - 760mmHg x 0.21 = 159mmHg
Mount Everest - 253mmHg x 0.21 = 59mmHg
75
Does the partial pressure of alveolar gasses increase or decrease with an increase in altitude?
They decrease
76
What does humidification mean for PO2 of inspired air?
Sea level - 159mmHg goes to 150mmHg
Mount Everest - 53mmHg to 40mmHg
77
Why does high altitude impose a diffusion limitation?
There is a decrease in the diffusion gradient for oxygen exchange
Decreased affinity of Hb for O2
Inadequate time for equilibration at gas exchange surface
78
What are the altitude levels?
High - 1500-3000m above sea
Very high - 3000-5000
Extreme - above 5000m
79
What height is Mount Everest?
8848m
80
Can you move to a higher altitude?
Sea level residents can move up to 4500-5000m
High altitude residents can move up to 5000-6000m
81
What are the acute respiratory responses to high altitude?
Increased breathing rate
Decreased pulmonary diffusion
Decreased saturation of Hb
Decrease in blood-tissue diffusion gradient
82
What are the chronic respiratory responses to high altitude?
Increased ventilation remain increased but stabilises
O poop luminary diffusion remains decreased
Saturation of Hb remains decreased
Blood-tissue gradient remains decreased
83
What are the steps to long term acclimatisation to high altitude?
Ascent to high altitude
Hypoxia
Carotid and aortic body stimulation (sensitivity may increases)
Respiratory centres stimulated
Increased ventilation
Decrease in PCO2
Increases pH
Increase in PO2
84
What happens to the oxyhaemoglobin dissociation curve when it shifts?
Left shift
- decreased temp
- Decreased 2-3DGP
- decreased [H+]
Right shift
- Reduced affinity
- Increased temp
- Increased 2-3 DGP
- Increased [H+]
85
What are the acute cardio response to high altitude?
Same or slightly decreased submaximal stroke volume
Increased submaximal HR
Increased submaximal cardiac output and BP
Decreased maximal stroke volume
Decreased maximal HR
Same or slightly lower maximal cardiac output
86
What are the chronic cardio response to high altitude?
Submaximal stroke volume decreases
Submaximal HR remains elevated
Decreased submaximal cardiac output to below sea level values
Maximal stroke volume remains decreased
Maximal HR remains decreased
Decreased maximal cardiac output
87
What are the acute haematologic responses to high altitude?
Decreased plasma volume
Increased haematocrit and Hb
Increased viscosity
88
What are the chronic haematologic responses to high altitude?
Plasma volume increases from acute but still remains decreased from normal
Increased RBC production keep haematocrit and Hb elevated
May be less viscous than acute
89
What happens during hypoxia?
Hypoxia
Erythropoietin (EPO)
Increased number of RBC (polycythaemia)
Increased haematocrit
Increased Hb
90
What are the disadvantages of EPO?
Increased viscosity
Increased coagulability
Increased risk of venous thromboembolism
91
Why is there a decrease in lean body mass and body fat at high altitude?
Increased metabolic rate (7-10%)
Decreased appetite (40-40%)
Decreases in total body water
Decreased absorption from the intestines
92
How long does it take to acclimatise to high altitudes?
2 weeks for altitudes <2,300m
For each increase of 610m after this is another week
93
How long do the benefits of high altitude training normally last for once you return to sea level?
Normally 2-3 weeks
94
What are the symptoms of high altitude deterioration?
Hyperventilation
Laboured breathing
Water loss
Frequent urination
Loss of appetite
Muscle atrophy
Mental stress
Lack of sleep
Heat loss
95
What is a general rule for sleeping when hiking at high altitudes?
When at >3000m sleeping elevation should increase by more than 300m per night
At every 1000m spend a 2nd night at the same elevation
96
What is the definition of mountain sickness?
Headache
+ one of the following:
- loss of appetite
- nausea or vomiting
- fatigue / weakness
- dizziness
- blue fingernails
- insomnia
97
What are the risk factors of acute mountain sickness?
Previous acute mountain sickness
Fast ascent
- >625m per day when above 2000m
Sleeping at altitude
98
What should you do if you begin to experience acute mountain sickness?
Descend to lower altitude
Hydrate
NSAIDs for headache
Anti-emetics for nausea
99
What are the two severe forms of altitude sickness?
Pulmonary
Cerebral oedema
100
What are the symptoms for pulmonary altitude sickness?
Dyspnoea upon exertion
Persistent dry cough
Pain/pressure in sub-sternal area
Headache
Nausea
Related to increase in pulmonary pressure
101
What are the symptoms of cerebral altitude sickness?
Disruption of vision, bladder and bowel function
Loss of co-ordination, paralysis
Poor reflexes
Mental confusion
Due to cerebral vasodilation and increased capillary hydrostatic pressure oedema and increased intracranial pressure
102
What is Monge’s disease?
Chronicle mountain sickness
103
Does acclimatisation help with Monge’s disease?
No there will still be
- excessive polycythemia
- pulmonary hypertension
- right sided heart failure
- decreased mental and physical capacity
