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Ocean Diver Lectures Flashcards

(51 cards)

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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?

Study These Flashcards
A

1) nitrogen management

2) ensuring sufficient breathing gas

22
Q

Describe nitrogen absorption on a dive.

Study These Flashcards
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?

Study These Flashcards
A

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

24
Q

What is current tissue code?

Study These Flashcards
A

Body’s present level of nitrogen saturation

25
What is surfacing code?
Represents a change to CTC at end of dive
26
Flying before diving?
Tissues off gas | 10 hour recovery before diving
27
Flying after diving?
Increased level of off-gassing - DCI | Need CTC of A or B
28
What do you need to plan a dive with tables?
Depth gauge Dive watch Dive slate
29
What are the functions of dive computers?
``` 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
How many dives can you do in 24 hours?
3
31
Advantages and disadvantages of nitrox?
Advantages: safety factor, reduced risk of DCI Disadvantages: can still get DCI, special equipment, oxygen toxicity
32
What is an EAD calculation?
Equivalent Air Depth | Calculated using nitrox tables NOT 88 - removes errors of calculation
33
Nitrox analysing essentials
``` 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
What is the rule of thirds? (and specific to 10L cylinder filled to 210 bar)
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
When does gas consumption increase?
Physical effort increases | Divers cold or anxious
36
Why do we dive with a buddy?
Monitor each other and assist Help in kitting up, entry and exit Develop skills with more experienced buddies
37
What is a DM responsible for?
All diving on site Selecting site Arranging buddy pair Gives dive brief
38
Info given on a DM brief?
Dive site info Hazards to avoid Surface support, assistant DM Separation procedure
39
What does A flag mean? What is the American version?
Divers down, stay clear and reduce speed USA: American Sports Divers Flag - divers below, stay clear
40
Describe the depths that colour absorbs at?
``` Red = 5m Orange = 10m Yellow = 15m Green = 20m Blue = 25m Indigo = 30m Purple = 40m ```
41
What reduces vis?
Suspended particles Turbidity Reduces light
42
What is the cause of DCI?
Inadequate elimination of nitrogen during ascent - bubbles | Gas embolism during ascent
43
Effects of DCI?
Bubbles can form in tissues - compress and damage vessels, reduces O2 delivery Bubbles can form in/ enter blood and block flow
44
What is the cause and effect of DCI - lung damage?
Cause: ascent too fast, breath hold Effects: over expansion, physical damage to lung tissue
45
DCI S&S?
``` Chest pain Voice change - crepitation SOB Itches/ rashes Joint aching N&T N&V Headache and confusion Weakness + paralysis ```
46
Narcosis - cause and signs?
Cause: nitrogen under pressure affects nerve impulse transmission Signs: effects of alcohol
47
Signs of o2 toxicity?
Visual/ auditory disturbances Muscle twitching Convulsions
48
Cause and detection of contaminated breathing air?
Cause: problems with compressor Detection: Oily taste
49
Effects of contaminated breathing gas?
Nausea, headaches, dizziness
50
Cause and resolution of out of air situation?
Cause: failure to monitor gas supply, equipment failure Resolution: AS, dive aborted
51
Cause and resolution of CBL?
Cause: unconscious buddy Resolution: get casualty to surface, ensure buoyant on surface

Diving (13 decks)

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