Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

HUMB3001 > W3 - Diving Physiology > Flashcards

W3 - Diving Physiology Flashcards

(87 cards)

Start Studying
1
Q

What law do gases follow?

A

Boyle’s Law

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is Boyle’s Law?

A

Pressure (p) of a given quantity of gas (n) varies inversely with its volume (v) at constant temperature (T)

P1 V1 = P2 V2

At 40 m below sea level (5 atmospheres) the volume is 1/5 of what it is at sea level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens during breath hold dive?

A

Volume of air in lungs gradually decreases with increasing depth

As pressure of gas increases, density increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is Dalton’s Law?

A

In gas mixture, an increase in total gas pressure is associated with an increase in partial pressures of gases by same proportion

P total = P 1 + P2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is Henry’s Law?

A

As partial pressure of gas is increased so the amounts of gas dissolved in body’s liquids increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the direct effects of increase pressure?

A

Cardiovascular changes (diving response)
Barotrauma
High pressure neurological syndrome (HPNS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe hydrostatic pressure.

A

pressure of the blood against the wall due to gravity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe blood pressure in body when on land in upright position

A

Gravity acting through longitudinal axis
Hydrostatic pressure gradient down body
BP in lower half of body increases
Result = pooling of blood in lower half

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe pressure gradients in body when surrounded by water

A

Equal external hydrostatic pressure gradient down body which opposes internal hydrostatic pressure gradient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is impact to blood when person is immersed in water?

A

500mL of blood moves from lower half of body to thoracic regions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is impact to CVS when person is immersed in water?

A

Incr in central blood volume = incr right atrial pressure = incr stroke volume = incr cardiac output = incr pulmonary blood flow = incr blood volume = incr pulmonary diffusing capacty

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is effect of increased central blood volume?

A

Decrease in release of vasopressin (ADH) (water absorption)

Increased secretion of atrial natriutic hormone (water secretion)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens on first immersion of body in water when colder than 15 deg C?

A

Heart rate falls
Breathing ceases
Selective vasoconstriction occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is effect of the diving response?

A

Heart rate falls
Breathing ceases
Selective vasoconstriction occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What causes diving response?

A

Stimulation of cutaneous receptors on face by cold water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is role of diving response?

A

Conserve oxygen in diving mammals
Decreasing workload of heart
Decreasing blood flow to most of systemic circulation except for brain/heart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What happens to air in lungs during breath hold dive?

A

As person goes deeper

Volume of air in lungs decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

When is breath hold dive a problem?

A

When volume of lung gases are compressed beyond residual volume

Causes negative intra-alveolar pressure = lung squeeze, pulmonary congestion, oedema, haemorrhage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What happens when diver with compressed air ascends?

A

Pulmonary barotrauma can occur

If driver fails to exhale during ascent or gas is trapped in area of lung = alveolar rupture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What happens during ascent of breath hold dive?

A

Gases in lung re-expand to original volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What must be given to divers when going deeper than 0.5 m?

A

Supplied with breathing mixture at a pressure equal to ambient pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is given to SCUBA divers?

A

Cylinder of compressed air (21% O2, 78% N2)

Demand valve ensures air is provided at pressure to match ambient pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What changes occur to gases under pressure?

A

Density of gases increases

Partial pressure of gases increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is effect of increased air density?

A

Increases inspiratory effort = work of breathing
Slow intra-alveolar diffusion of gases
Reduced maximum aerobic capacity (VO2 max)

Reduce by replacing N2 with helium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
When does nitrogen narcosis occur?
When compressed air is used during diving, partial pressure of nitrogen increases and symptoms develop at 30 m below sea (4 atm)
26
What are raptures of the deep?
Symptoms of nitrogen narcosis
27
What are symtpoms of nitrogen narcosis?
``` Resemble alcohol intoxication Euphoria Irrational Reduced dexterity Reduced mental agility ```
28
What depths does nitrogen narcosis cause unconsiousness?
Beyond 90 msw (10 atm)
29
How does nitrogen produce narcosis?
Nitrogen causes small change in membrane volume Leads to modulation of ion channels Disruption of excitability of axons Impairment of synaptic transmission
30
What is HPNS?
High pressure neurological syndrome
31
What parts of body compress at higher pressures?
Lipids more compressible than water | Gases
32
What causes HPNS?
Compression of lipids in cell membranes of neurons | Changes permeability and transport properties
33
What are symptoms of HPNS?
Tremor Decr manual dexterity Dizziness Nausea
34
What depths (atmospheres) is HPNS seen?
Below 200 msw or over 21 atm Severe when rate of descent is rapid
35
What happens when PO2 rises above 1350mmHg?
Oxygen is toxic to nervous system Can cause epileptic type convulsions Preceded by vertigo, nausea, paraesthesia of arms/legs, twitching muscles around eye/mouth
36
What depth do you reach toxic PO2 when breathing pure oxygen?
8 msw (when PO2 is 1.8 atm = 1350 mmHg)
37
Why is oxygen toxic to CNS?
Possibly due to oxidation of sulphydryl groups found in some enzymes and membrane protiens Disrupt function and hyperexcitability of neurons
38
What are initial symptoms of pulmonary oxygen toxicity?
Coughing -> dyspnoea (difficult breathing) -> pulmonary oedema -> intra-alveolar haemorrhage
39
What causes symptoms of pulmonary oxygen toxicity?
Progressive destruction of alveolar endothelial and epithelial cells
40
What PO2 can pulmonary toxicity develop in?
As little as 375mmHg (0.5 atm) so when 16 msw (compressed air) Symptoms appear after > 30h
41
What gas mixture do divers use for below 50 msw?
Helium oxygen mixture
42
Why is helium used in mixtures?
1/8 th narcotic effects of nitrogen so higher PP can be withstood 1/7th density of nitrogen so work of breathing is reduced Solubility is 40% of nitrogen Reduces likelihood of decompression sickness
43
Describe important of heliox mixture.
Ratio of helium - oxygen is adjusted so PO2 does not exceed 300 mmHg At 100msw, % O2 used is 4.4% At 300msw, % O2 used is 1.26%
44
What are other effects of helium?
High thermal conductivity = increased resp heat losses Helium elevates pitch of voice (low density)
45
What is trimix and what depths used for?
Mixture of O2, N2, Helium Deeper than 50m (non-recreational)
46
Why was trimix developed?
Exploit the known depressant effect of nitrogen on NS to offset excitatory effects of high pressure
47
What depths can be achieved with trimix?
> 650m
48
Describe dissolution of N2 in body solution in diving descent.
At sea level: 1L of N2 in solution Every 10m: Another 1L of N2 more New equilibrium is not attained immediately
49
Describe equilibrium process of N2 in body
Blood volume is 8% of body volume so takes time for nitrogen to be transported to tissues and reach equilibrium ``` Well perfused tissues (brain) take up N2 and reach equilibrium quickly Adipose tissue (slower perfusion) reaches equilibrium slower ``` Usually takes 6-8h for all tissues to reach equilibrium
50
Define saturation diving.
When tissues reach equilibrium of the inhaled gases
51
What is the problem with gas mixtures when diving?
Not with uptake but problems to eliminate them when decompression takes place on ascent
52
What happens to gases when divers ascend?
Inspired gas pressures fall Partial pressure gradient for gases develops between tissues and alveoli Extra gases diffuse from tissues into blood to be eliminated in lungs
53
Describe effect when rate of ascent is rapid.
There is maximal rate at which gases can be eliminated If quantity of gases dissolved in tissues is large, tissues become supersaturated causing them to come out of solution and form bubbles Decompression sickness = bends
54
Which type of gases are important in decompression sickness?
Inert gas bubbles that cannot be utilised by tissues
55
What can O2 bubbles be used for?
Locally in tissue metabolism
56
What is impect of body fat % on decompression?
Higher body fat means more nitrogen stored which needs to be eliminated
57
What is example of barotrauma?
Alveoli ruptured and gas escapes into pleural cavity causing pneumothroax
58
Describe cause of cerebral arterial gas embolism
Aveoli ruptured, gas escape into pulmonary circulation where reaches systemic circulation Pass upwards via carotid arteries to cerebral circulation
59
What are symptoms and treatment of cerebral arterial gas embolism?
Stroke like symptoms, lose consciousness | Treated by recompression to 6 atm
60
What is effect of high pressure on rigid body cavities e.g. paranasal sinus/middle ear?
Not free to undergo change in volume Bound by rigid structures If pressure of gas cannot equilibrate with ambient pressure Risk of damage to structures
61
What is effect of high pressures on mucosal linings of cavities?
Large transmural (across entire BV) pressure across vasculature will lead to exudation of fluid Can lead to rupture of capillaries
62
How is barotrauma to middle ear prevented?
By equilibrating pressure in middle ear with ambient pressure
63
What happens if Eustachian tube entrance is blocked/inflamed during high pressure?
Equilibration may become impossible | Descent causes significant pressure gradient to develop across tympanic membrane = bulge inwards = pain
64
What happens if channels between paranasal sinus to nasopharynx are blocked (sinusitis) during descent?
Equalisation cannot occur | Haemorrhage of lining of sinuses and intense pain
65
List some scuba diving hazards resulting from inability to equalise pressure.
``` Air embolism in brain Face mask squeeze = rupture BV in eyes, suck eyes from sockets Mediastinal and subcutaneous emphysema Pneumothorax Alveoli ruptured ```
66
What is underlying cause of decompression sickness?
Formation of inert gas bubbles
67
When does decompression sickness cause overt symptoms?
When bubbles reach some critical size
68
What factors predispose people to decompression sickness?
Obesity Poor physical condition Age Exertion
69
What are the 3 theories of why bubbles cause decompression sickness?
Direct mechanical effects of EC bubbles, distorting tissues, blocking capillaries Cellular damage due to intracellular gases Changes in vascular endothelium, aggregation of intravascular fat, imposed by intravascular bubbles
70
When do signs and symptoms of decompression sickness occur?
90% appear within 6h | May not occur until 36h after
71
What is most common symptom of decompression sickness?
Pain in joints of extremities (shoulder, elbow, knee) = formation of bubbles in ligaments, tendons
72
Where do larger intravascular bubbles usually get trapped?
Pulmonary vascular bed
73
What happens to bubbles in pulmonary vascular bed?
Block pulmonary capillaries | Causes severe dyspnoea and cough
74
What is chokes?
Severe dyspnoea and cough from bubbles trapped in pulmonary vascular bed
75
What causes serious form of decompression sickness?
When bubbles form in spinal cord or when intravascular bubbles block circulation to cord Degenerates nerve fibers causing motor/sensory deficits = permanent paralysis
76
What is staggers?
Bubble formation in vestibular apparatus
77
What is bone avascular necrosis?
Bubbles blocking end artiers of bone causing bone to die Head/neck/shaft of long bones (upper humerus, upper/lower femur, upper tibia)
78
How is decompression sickness avoided?
Select rate of ascent that precludes significant bubble formation Use decompression table
79
What did Haldane suggest about bubble formation?
Significant bubble formation would not occur if total tissue gas pressure did not exceed 2x ambient pressure
80
What are decompression tables?
Shows divers how to ascend Where to stop (depths) Where ambient pressure is half of that at the depth of previous stop How long to stop to allow inert gas to be eliminated (equilibrium attained)
81
What ascent is recommended after diving to 20 msw for 2h?
2 stops taking 50 min in total
82
What ascent is recommended after diving to 50 msw for 45min?
5 stops, total 85 min
83
What is decompression time for diving at 100 msw?
4 days
84
What is decompression time for diving at 300 msw?
10 days
85
What actions must divers avoid after diving?
Avoid flying in aircraft | Ambient pressure in aircraft is less than normal pressure so further decrease in pressure can cause bubble formation
86
What are some other problems associated with diving?
Density of water increases effort to move Difficult to use tools with torque due to buoyancy Visibility is impaired Hearing is impaired Cold (water conducts heat away)
87
Describe impact of cold water in diving.
Water surrounding diver conducts heat away from body surface Wet suit can be used but thermal insulation decreases with increasing depth due to compression of suit Heliox exaggerates heat loss (incr respiratory heat loss) Need own central heating system = electrically heated suit/hot water piped in suit

HUMB3001 (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions