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diving > Ocean Diver Lectures > Flashcards

Ocean Diver Lectures Flashcards

1
Q

Benefits of BSAC Membership

A 
Largest club in world
Internationally recognised qualifications
Diving Manual
SCUBA magazine
3rd party Insurance 
Member's prices in shop
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2
Q

Benefits of diving with a branch

A 
Branch support
Planned diary of dives
Range of diving buddies and interests
Sharing the experience 
Branch dive trips and holidays
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3
Q

Aim of OD course?

A

Train a diver who can use 21%, 32% and 36% O2 mixes in controlled conditions to a depth of 20m under the supervision of a DM

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4
Q

Describe the OD course

A

7 lectures, theory assessment, 5 sheltered water, 5 open water

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5
Q

Describe atmospheric pressure

A

Weight of air in 1cm square column of the atmosphere
=1kg/cm^2
=1 bar

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6
Q

What is water pressure?

A

Water exerts pressure of 1 bar for every 10m of depth

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7
Q

What is absolute pressure?

A

= gauge pressure + atmospheric pressure

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8
Q

Describe the structure of a mask.

A

Has tempered glass, a frame and a flexible seal with adjustable strap

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9
Q

How big is a snorkel?

A

40-45cm long

20mm diameter

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10
Q

What is Boyles Law?

A

For a fixed mass of gas at constant temperature, the pressure is inversely proportional to the volume

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11
Q

What does SCUBA stand for?

A

Self Contained Underwater Breathing Apparatus

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12
Q

Describe when a cylinder is tested and to what standard.

A

BS/EN standard
Has a working and a test pressure
Hydraulic testing every 5 years
Visual every 2.5 years

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13
Q

What is the composition of our exhaled breath?

A

17% oxygen
4% CO2
79% nitrogen

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14
Q

What happens with a breath hold dive with hyperventilation?

A

O2 level to support consciousness begins high and drops, because CO2 level for stimulus to breathe doesn’t reach threshold

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15
Q

Describe the effects of diving on the ear.

A

Sound travels faster underwater - direction difficult to identify
Air spaces - ear drum, middle ear and Eustachian tube

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16
Q

Describe heat loss when diving.

A

25 times faster than air
Cold water increases rate of heat loss
End dive if getting cold

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17
Q

When do we need thermal insulation when diving?

A 
20C+ = no suit required
10-20C = wetsuit or drysuit required
0-10C = drysuit required
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18
Q

What is sinus squeeze?

A

When there is no equalisation between sinuses and ambient pressure
Mucus membranes swell to relieve pressure
Blood vessels burst

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19
Q

Sinus pain

A

If a diver feels pain in sinuses during descent they should abort dive (indicative of damage to sinus nerves)

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20
Q

What is Archimedes Principle?

A

When an object floats in water it displaces a weight of water equal to its own weight

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21
Q

What are the 2 most important considerations in planning a dive?

A

1) nitrogen management

2) ensuring sufficient breathing gas

22
Q

Describe nitrogen absorption on a dive.

A

Increase in ambient pressure results in more nitrogen being absorbed - on gassing
Fast tissues = good blood supply
Slow tissues = poor blood supply eg fat

23
Q

What is the maximum descent and ascent rate?

A

Descent = 30m/ minute
Ascent = 15m/min up to 6m
1 minute from 6m to surface

24
Q

What is current tissue code?

A

Body’s present level of nitrogen saturation

25
Q

What is surfacing code?

A

Represents a change to CTC at end of dive

26
Q

Flying before diving?

A

Tissues off gas

10 hour recovery before diving

27
Q

Flying after diving?

A

Increased level of off-gassing - DCI

Need CTC of A or B

28
Q

What do you need to plan a dive with tables?

A

Depth gauge
Dive watch
Dive slate

29
Q

What are the functions of dive computers?

A 
Theoretical body tissue models to calculate nitrogen on and off gassing
Timer and pressure sensor
Planning info eg depth and time
Audible/ screen warnings 
Stored log of previous dives 
Temp sensors
30
Q

How many dives can you do in 24 hours?

A

3

31
Q

Advantages and disadvantages of nitrox?

A

Advantages: safety factor, reduced risk of DCI
Disadvantages: can still get DCI, special equipment, oxygen toxicity

32
Q

What is an EAD calculation?

A

Equivalent Air Depth

Calculated using nitrox tables NOT 88 - removes errors of calculation

33
Q

Nitrox analysing essentials

A 
Calibrate prior to use 
Keep flow rate even and low 
Avoid windy conditions
Avoid moisture
Analysis must be within +/- 1% of your target mix
34
Q

What is the rule of thirds? (and specific to 10L cylinder filled to 210 bar)

A

1/3 gas for descent to half way point
1/3 gas for second half of dive
1/3 gas as reserve

210/3 = 70 bar for each 1/3
140 bar for dive

35
Q

When does gas consumption increase?

A

Physical effort increases

Divers cold or anxious

36
Q

Why do we dive with a buddy?

A

Monitor each other and assist
Help in kitting up, entry and exit
Develop skills with more experienced buddies

37
Q

What is a DM responsible for?

A

All diving on site
Selecting site
Arranging buddy pair
Gives dive brief

38
Q

Info given on a DM brief?

A

Dive site info
Hazards to avoid
Surface support, assistant DM
Separation procedure

39
Q

What does A flag mean? What is the American version?

A

Divers down, stay clear and reduce speed

USA: American Sports Divers Flag - divers below, stay clear

40
Q

Describe the depths that colour absorbs at?

A 
Red = 5m
Orange = 10m
Yellow = 15m
Green = 20m
Blue = 25m
Indigo = 30m
Purple = 40m
41
Q

What reduces vis?

A

Suspended particles
Turbidity
Reduces light

42
Q

What is the cause of DCI?

A

Inadequate elimination of nitrogen during ascent - bubbles

Gas embolism during ascent

43
Q

Effects of DCI?

A

Bubbles can form in tissues - compress and damage vessels, reduces O2 delivery
Bubbles can form in/ enter blood and block flow

44
Q

What is the cause and effect of DCI - lung damage?

A

Cause: ascent too fast, breath hold
Effects: over expansion, physical damage to lung tissue

45
Q

DCI S&S?

A 
Chest pain
Voice change - crepitation
SOB
Itches/ rashes
Joint aching
N&T
N&V
Headache and confusion 
Weakness + paralysis
46
Q

Narcosis - cause and signs?

A

Cause: nitrogen under pressure affects nerve impulse transmission
Signs: effects of alcohol

47
Q

Signs of o2 toxicity?

A

Visual/ auditory disturbances
Muscle twitching
Convulsions

48
Q

Cause and detection of contaminated breathing air?

A

Cause: problems with compressor
Detection: Oily taste

49
Q

Effects of contaminated breathing gas?

A

Nausea, headaches, dizziness

50
Q

Cause and resolution of out of air situation?

A

Cause: failure to monitor gas supply, equipment failure
Resolution: AS, dive aborted

51
Q

Cause and resolution of CBL?

A

Cause: unconscious buddy
Resolution: get casualty to surface, ensure buoyant on surface

diving (13 decks)

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