DM Chapter 9 Dive Theory Review

Question 1

Why is a solid understanding of dive theory important?

Answer 1

1. Answer questions.
2. Solve problems that aren’t easily predicted or defined.
3. Understand relationships, causes and effects.
4. Function as a dive leader.

Question 2

Water dissipates body heat faster than air does, because it absorbs heat approximately (blank) times faster than air does.

Answer 2

20

Question 3

Light (blank) when it passes through a substance of one density into a substance of a different density.

Answer 3

changes speed and directions

Question 4

Due to refraction, underwater objects appear to be magnified by a factor of

Answer 4

4/3

Question 5

Sounds travel faster in water than in air, because water is denser (more elasticity) than does air. T/F

Answer 5

True

Question 6

Sounds travels approximately (blank) times faster in water than in air.

Answer 6

4

Question 7

Beacuse sound travels faster underwater, it is (blank) to determine the direction a sound is coming from while diving.

Answer 7

more difficult

Question 8

Depth = Pressure
00 ft =
33 ft =
66 ft =
99 ft =
132 ft =

Answer 8

Depth = Pressure
00 ft = 1 ata
33 ft = 2 ata
66 ft = 3 ata
99 ft = 4 ata
132 ft = 5 ata

Question 9

Absolute pressure

Answer 9

The total pressure, which is what you typically need to understand the effects of pressureon gases and your body.

Question 10

Gauge pressure

Answer 10

Uses 1 ata as the zero point.

Pressure reading used by most gauges.

Question 11

Ambient pressure

Answer 11

Surrounding pressure.

The pressure that exists around something at a defined moment.

Pressure on a diver at a given depth.

Question 12

What is the absolute pressure at 79 feet in the ocean?

Answer 12

(79 / 33) + 1 = 3.4 ata

Question 13

Depth =
Pressure =
Air volume =
Air Density =

Answer 13

00 ft = 1 ata = 1 = (x1)
33 ft = 2 ata = 1/2 = (x2)
66 ft = 3 ata = 1/3 = (x3)
99 ft = 4 ata = 1/4 = (x4)

Question 14

If a diver is in fresh water at 34 feet, what is the ambient pressure?

Answer 14

2 ata

Question 15

A diver in seawater at 66 feet brings a balloon of air to the surface. Assuming the balloon will not burst, its volume will be (blank) what it was at depth.

Answer 15

Three times

Question 16

The density of a gas will be (blank) at 99 feet what it is at 33 feet.

Answer 16

Two times

Question 17

What will increase an object’s buoyance?

Answer 17

1. Increase displacement
2. Reduce weight

Question 18

Partial pressure

Answer 18

1. The proportion of the total pressure exerted by a gas mixture that an individual gas exerts.
2. Determined by multiplying the percent of the gas times the absolute pressure.
3. Related to the solution of gases in liquid.

Question 19

What is the primary control of breathing called?

Answer 19

Reflex respiratory center

Question 20

What is ‘dead air’?

Answer 20

Gas that remains in your sinuses, trachea and bronchi.

Question 21

What is the most efficient way to breathe?

Answer 21

Breathe from diaphragm.

Abdomen should expand outward.

Diaphragm breathing draws air into the lower part of the lungs where about 75% of gas exchange takes place.

Question 22

What are the two types of O2 toxicity?

Answer 22

1. Central nervous system.
2. Pulmonary toxicity

Question 23

CNS Toxicity

Answer 23

1. Immediate, life threatening threat.
2. Risk becomes unacceptable when the PO2 exceeds approximately 1.4 ata AND a diver is active.
3. Most severe sign is convulsion.

Question 24

VENTID

Answer 24

V = visual disturbance
E = ears ringing
N = nausea
T = twitching muscles
I = irritability
D = dizziness and vertigo

Question 25

Pulmonary O2 toxicity

Answer 25

1. Results from continuous or repeated exposure to PO2 above 0.5 ata. 2. Reaction occurs in the lungs. 3. S/S burning in chest and an irritating cough.

Question 26

To avoid CNS oxygen toxicity, do not exceed a PO2 of

Answer 26

1.4 ata

Question 27

Gas narcosis

Answer 27

Narcotic effect that gases can cause when breathed under elevated partial pressures. Type of anesthesia.

Question 28

Type I DCS

Answer 28

1. Not immediately life threatening. 2. Pain only - limb and joint pain.

Question 29

Skin bends

Answer 29

Cutaneous DCS that forms a rash. Is considered Type I if it occurs by itself.

Question 30

Type II DCS

Answer 30

1. Life threatening or debilitating. 2. Neurological DCS. 3. Stroke like symptoms/signs. 4. Pulmonary DCS

Question 31

DCI = Decompression Illness

Answer 31

Overall term that includes both DCS and lung overexpansion injuries.

Question 32

Body response to excess heat.

Answer 32

1. Skin capillaries dilate 2. Perspiration 3. Increase pulse

Question 33

Signs/Symptoms of Heat Exhaustion

Answer 33

1. Weak and rapid pulse 2. Profuse sweating 3. Cool/clammy skin 4. Nausea 5. Weakness

Question 34

Signs/Symptoms of Heat Stroke

Answer 34

1. Cessation of perspiration 2. Skin hot and flushed 3. Strong and rapid pulse

Question 35

A long, forceful equalization can cause window rupture. T/F

Answer 35

True

Question 36

Burst disk

Answer 36

1. Part of the valve 2. Ruptures if cylinder exceeds 140% of working pressure 3. Thin cooper disk

Question 37

When gas flows to the second stage, pressure drops in the first stage intermediate pressure chamber. This causes the

Answer 37

first stage diaphragm/piston to open a valve releasing gas from the cylinder.

Question 38

An (blank) depth gauge operates on the principle of pressur causing a sealed coiled tube to coil tighter.

Answer 38

oil filled bourdon tube

Question 39

Electronic depth gauges and electronic SPGs both use a (blank)

Answer 39

transducer

Question 40

A mechanical SPG that reads high may be close to failure. T/F

Answer 40

True

Question 41

To account for the fact that the body doesn't absorb and release inert gas on a single time scale, Haldanean models have several (blank)

Answer 41

tissue compartments

Question 42

The maximum value of a tissue compartment is represented by its (blank)

Answer 42

M - Value

Question 43

How fast a tissue compartment absorbs and releases gas is represented by its (blank)

Answer 43

halftime