Chapter 2 - Physics And Physiology Of Diving Flashcards
What is the pressure at sea level?
1 kg/cm^2-
1 bar
What is the pressure like 5000m above sea level?
0.5 bar
What happens when you increase depth by 10m?
The pressure increases by 1 bar
What is ambient pressure?
Pressure of air around you
What is absolute pressure?
Pressure in total measured against a vacuum.
What is gauge pressure?
Pressure measured on a gauge calibrated to zero at sea level. Gauge pressure is zero when absolute pressure is 1 bar
How can you calculate absolute pressure?
Absolute pressure = gauge pressure + atmospheric pressure
How can you remember the difference between gauge and absolute pressure?
When your tank is empty the gauge pressure is 0 but the absolute pressure is 1 bar
How can you calculate absolute pressure?
Depth (m) / 10 + atmospheric pressure
How can you work out depth?
Depth = (absolute pressure - atmospheric pressure) x 10
What are the units of capacity/volume?
Litre
1000l = 1 cubic metre
What is the mass of 1 L of fresh water equivalent to?
1 kg
What are the units of pressure?
1 bar - 1 kg per square cm
What is the density of salt water and density of fresh water?
1030 kg/m3
1000 kg/m3
What is boyles law?
Volume of a given mass varies inversely to its absolute pressure as long as temperature remains constant.
How does boyles law work?
As pressure increases the volume decreases
How can boyles law be stated?
P1 V1 = P2 V2
Where is the greatest change of pressure?
Within the first 10m
What is barotrauma?
Pressure damage
Which tube in the middle ear allows you to equalise?
The Eustachian tube
What is the valsalva manoeuvre?
Ear clearing
What are the symptoms of barotrauma caused by decent?
An experience of vertigo, nausea and anxiety
If water enters the ear from barotrauma how long can the recovery time be?
1-3 months
What is reversed ear?
When the pressure in the middle ear is greater than the outer ear
Why should you not dive with a cold?
You can have nosebleeds or other fluids escaping your nose in the water
What is the metabolism equation?
Food + oxygen = energy + waste products removal (water and co2)
What is the total lung capacity of the average human?
6 litres
What is the residual volume?
The 1-1 1/2 litres of air that must remain in the lungs so they keep the correct shape
What is the vital capacity?
The 4 1/2 - 5 litres that represents the maximum amount of air that can be inhaled and exhaled in one respiratory cycle
What is the tidal volume?
The amount of air inhaled and exhaled
What is the tidal volume at rest?
0.5litres
What is the dead air space?
The portion of the tidal volume that plays no part in the gas exchange
What is an oral nasal shroud used for?
Used in full face masks to reduce the dead air space
What is the average number of breaths per minute?
12-20
How many breaths do you take per minute when exercising?
35
What causes you to take a breath?
The rising levels of carbon dioxide in the blood
What are the characteristics of blood?
It’s both solid (45%) and liquid (55%)
What is the liquid part of the blood?
Plasma - 90-92% water
What is the solid element of the blood like?
Made from…
Thrombocytes (platelets) - natural clotting
Erythrocytes (red blood cells) - carry oxygen
Leucocytes (white blood cells) - defend against germs and infections
What are the functions of the blood?
Transportation
Clotting to minimise the loss of body fluids
Defence system
Regulate body temperature - vasodilation or vasoconstriction
What does blood transport?
Oxygen from lungs to tissue CO2 from tissues to lungs Nutrients from the digestive tract to the cells Waste products Hormones and enzymes
What is the cardiac cycle?
- Blood returns via the vena cava to the right atrium
- Passes to the right ventricle
- Pumped out of the heart into the pulmonary artery to the lungs
- Gas exchange
- Oxygenated blood returns to the left atrium
- Blood passes to the left ventricle
- Blood is pumped into the aorta for body distribution
What is the rule of thumb around blood transportation?
Veins carry de-oxygenated blood to the heart
Arteries carry oxygen rich blood away from the heart
The exception is the pulmonary vessels
What is the average pulse rate?
60-90 beats per minute
What are the 3 types of blood vessels?
Arteries - thick muscular walls - cope with blood being pumped under pressure
Veins - very little muscular tissue - May have semi-lunar valves to prevent the back flow of blood
Capillaries - small vessels - permit the transfer of fluids, nutrients and gasses
What is Archimedes principle?
A body immersed in a fluid experiences an up thrust equal to the mass of the fluid displaced
What happens with the different types of buoyancy?
Positive - float
Neutral - hover
Negative - sink
