DM Chapter 9 Dive Theory Review Flashcards
Why is a solid understanding of dive theory important?
- Answer questions.
- Solve problems that aren’t easily predicted or defined.
- Understand relationships, causes and effects.
- Function as a dive leader.
Water dissipates body heat faster than air does, because it absorbs heat approximately (blank) times faster than air does.
20
Light (blank) when it passes through a substance of one density into a substance of a different density.
changes speed and directions
Due to refraction, underwater objects appear to be magnified by a factor of
4/3
Sounds travel faster in water than in air, because water is denser (more elasticity) than does air. T/F
True
Sounds travels approximately (blank) times faster in water than in air.
4
Beacuse sound travels faster underwater, it is (blank) to determine the direction a sound is coming from while diving.
more difficult
Depth = Pressure
00 ft =
33 ft =
66 ft =
99 ft =
132 ft =
Depth = Pressure
00 ft = 1 ata
33 ft = 2 ata
66 ft = 3 ata
99 ft = 4 ata
132 ft = 5 ata
Absolute pressure
The total pressure, which is what you typically need to understand the effects of pressureon gases and your body.
Gauge pressure
Uses 1 ata as the zero point.
Pressure reading used by most gauges.
Ambient pressure
Surrounding pressure.
The pressure that exists around something at a defined moment.
Pressure on a diver at a given depth.
What is the absolute pressure at 79 feet in the ocean?
(79 / 33) + 1 = 3.4 ata
Depth =
Pressure =
Air volume =
Air Density =
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)
If a diver is in fresh water at 34 feet, what is the ambient pressure?
2 ata
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.
Three times
The density of a gas will be (blank) at 99 feet what it is at 33 feet.
Two times
What will increase an object’s buoyance?
- Increase displacement
- Reduce weight
Partial pressure
- The proportion of the total pressure exerted by a gas mixture that an individual gas exerts.
- Determined by multiplying the percent of the gas times the absolute pressure.
- Related to the solution of gases in liquid.
What is the primary control of breathing called?
Reflex respiratory center
What is ‘dead air’?
Gas that remains in your sinuses, trachea and bronchi.
What is the most efficient way to breathe?
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.
What are the two types of O2 toxicity?
- Central nervous system.
- Pulmonary toxicity
CNS Toxicity
- Immediate, life threatening threat.
- Risk becomes unacceptable when the PO2 exceeds approximately 1.4 ata AND a diver is active.
- Most severe sign is convulsion.
VENTID
V = visual disturbance
E = ears ringing
N = nausea
T = twitching muscles
I = irritability
D = dizziness and vertigo
Pulmonary O2 toxicity
- Results from continuous or repeated exposure to PO2 above 0.5 ata.
- Reaction occurs in the lungs.
- S/S burning in chest and an irritating cough.
To avoid CNS oxygen toxicity, do not exceed a PO2 of
1.4 ata
Gas narcosis
Narcotic effect that gases can cause when breathed under elevated partial pressures.
Type of anesthesia.
Type I DCS
- Not immediately life threatening.
- Pain only - limb and joint pain.
Skin bends
Cutaneous DCS that forms a rash.
Is considered Type I if it occurs by itself.
Type II DCS
- Life threatening or debilitating.
- Neurological DCS.
- Stroke like symptoms/signs.
- Pulmonary DCS
DCI = Decompression Illness
Overall term that includes both DCS and lung overexpansion injuries.
Body response to excess heat.
- Skin capillaries dilate
- Perspiration
- Increase pulse
Signs/Symptoms of Heat Exhaustion
- Weak and rapid pulse
- Profuse sweating
- Cool/clammy skin
- Nausea
- Weakness
Signs/Symptoms of Heat Stroke
- Cessation of perspiration
- Skin hot and flushed
- Strong and rapid pulse
A long, forceful equalization can cause window rupture. T/F
True
Burst disk
- Part of the valve
- Ruptures if cylinder exceeds 140% of working pressure
- Thin cooper disk
When gas flows to the second stage, pressure drops in the first stage intermediate pressure chamber. This causes the
first stage diaphragm/piston to open a valve releasing gas from the cylinder.
An (blank) depth gauge operates on the principle of pressur causing a sealed coiled tube to coil tighter.
oil filled bourdon tube
Electronic depth gauges and electronic SPGs both use a (blank)
transducer
A mechanical SPG that reads high may be close to failure. T/F
True
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)
tissue compartments
The maximum value of a tissue compartment is represented by its (blank)
M - Value
How fast a tissue compartment absorbs and releases gas is represented by its (blank)
halftime
