01.1 Respiration Basics and Gas Laws

Question 1

What is atmospheric pressure at sea level?

Answer 1

101kPa
1Atm
760mmHg

Question 2

What is the kinetic theory of gas pressure?

Answer 2

Gas molecules randomly move in space.
Pressure is generated by the collisions of molecules with a surface.
The more frequent and hard the collisions are the higher the pressure.

Question 3

What is partial pressure?

Answer 3

The pressure that an individual gas exerts (as molecules in a gas mixture behave independently)

Question 4

How is partial pressure calculated?

Answer 4

Total pressure X volume percentage of that gas

Question 5

What is Boyle’s law?

Answer 5

Pressure of gas is inversely proportional to volume.

Question 6

What happens to pressure at altitude?

Answer 6

Decreases.

Question 7

What is Charle’s law and why is it not really applicable in medicine?

Answer 7

If volume and quantity of gas is constant, pressure is directly proportional to absolute temperature.
Not really useful in medicine as temperature is usually constant across the alveoli membrane.

Question 8

What also exerts a pressure in the lungs as well as the gases from the environment?

Answer 8

Water vapour exerts a saturated vapour pressure (SVP)

Question 9

How is saturated vapour pressure taken into account for when calculating partial pressure of a gas in the mixture?

Answer 9

You take away SVP (6.28kPa) from the total pressure before dividing by the percentage volume of the gas.

Question 10

What does the tension pressure in the liquid equal?

Answer 10

The same as the partial pressure in the gas mixture if in equilibrium.

Question 11

If a reaction occurs between the gas and a component of the liquid, does this happen before or after tension is established?

Answer 11

The reaction must occur before tension is established

Total content = reacted gas + dissolved gas

Question 12

What is the general proportion of haemoglobin bound oxygen to dissolved oxygen?

Answer 12

Hb bound is a much greater proportion of the total than dissolved (roughly 80x).

Question 13

What is the bends?

Answer 13

Decompression sickness.
Nitrogen moves from high pressure in the lungs to the blood when below surface.
A slow return allows the nitrogen to return to the lungs where it is breathed out.
Swimming up to quickly doesn’t give nitrogen enough time to leave the blood so it comes out of solution as bubbles.

Question 14

What is the molecular composition of air?

Answer 14

N2 - 78%
O2 - 21%
Other - 1%