Week 1 - Overview

Question 1

Define inspiratory reserve volume

Answer 1

-Extra volume that can be breathed in over that at rest

Question 2

Define expiratory reserve volume

Answer 2

-Extra volume which can be breathed out over that at rest

Question 3

What is atmospheric pressure at sea level?

Answer 3

-101 kPa

Question 4

What is partial pressure? What is it proportional to?

Answer 4

• The individual pressure a gas exerts within a mixture

- Partial pressure is proportional to the volume of gas in the mixture eg 21% o2 will generate 21% of total pressure

Question 5

How do you calculate pp?

Answer 5

-Total pressure x % volume of gas

eg ppO2 = 101x20.9%=21.1kPa

Question 6

What is boyles law?

Answer 6

-The pressure of gas is inversely proportional to the volume (giving that temp and amount remain constant)

Question 7

What happens to the pressure in the lungs as the chest expands? What effect does this have on volume?

Answer 7

• Pressure decreases below atm. pressure as lungs expand

- This causes air to flow into the lungs from the atmosphere

Question 8

What happens to the pressure in the lungs during expiration and what effect does this have on volume?

Answer 8

• As lung size decreases the pressure of air in the lungs rises above atm. pressure
• This causes air to flow out into the atm.

Question 9

Why is atm pressure decreased at higher altitude?

Answer 9

• the mass of gas pressing down from higher in the atm is reduced
• air molecules are more dispersed and thus pressure is less

Question 10

What effect does a reduced total atm. pressure have on partial pressure of oxygen and thus o2 availability?

Answer 10

• Reduces pO2 and thus availability

- eg 31.1kPa x 21%= 6.5kPa of O2 as opposed to 21kPa at atm. pressure

Question 11

What is charles law?

Answer 11

-If the volume and amount of gas is constant, pressure is directly proportional to absolute temperature

Question 12

Why is it significant that gases are always in contact with water within the body?

Answer 12

-Water will evaporate into the gas phase and gas will condense into the liquid phase

Question 13

What is saturated vapour pressure? What is it dependant upon?

Answer 13

• the pressure exerted by water as it evaporates into the gas phase and reaches an equilibrium with gas condensing into liquid phase
• Dependant only upon temperature -> 6.28kPa at 37degrees

Question 14

What effect does saturated water pressure have on pO2 in the airways?

Answer 14

-Decreases
-SVP contributes to the total pressure of air in the airways reducing the % of oxygen available
eg 101-6.28=94.72
94.71x21%=19.7kPa (rather than 21.1kPa outside the body)

Question 15

What is tidal volume?

Answer 15

-The total amount of air inspired and expired from a normal expiration

Question 16

What is gas tension? What is it equal to?

Answer 16

• The pressure exerted by a gas as it dissolves into liquid which has reached equilibrium
• Equal to the partial pressure of gas in the gas mixture

Question 17

Under normal circumstances, is there a difference between the pO2 in the alveolus and the gas tension of oxygen in arterial plasma?

Answer 17

-No they will be the same

Question 18

How do you calculate the amount of gas within a liquid?

Answer 18

-Solubility x tension (pp)

Question 19

What two components make up total gas content?

Answer 19

-Reacted gas+dissolved gas

Question 20

What is the solubility coefficient of O2 at 37 degrees?

Answer 20

-0.01mmol/L/kPa

Question 21

How much O2 does Hb bind at 13.3kPa?

Answer 21

-8.8mmol/L

Question 22

Under normal conditions, What is the total O2 content of the blood?

Answer 22

-8.93 (Hb+dissolved O2)

Question 23

Where does the respiratory portion of the airways begin?

Answer 23

-After terminal bronchioles (resp bronchioles, alveolar ducts and alveolar sacs)

Question 24

What is hypoxic pulmonary vasoconstriction?

Answer 24

• Matches ventilation to perfusion
• Areas which are poorly perfused or ventilated undergo vasoconstriction to divert blood to those areas which are well perfused and ventilated

Question 25

What is the bends?

Answer 25

• Occurs in scuba divers
• The air inspired is under a higher pressure, increases partial pressure of O2 and N
• N moves from areas of high pressure in the lungs into the blood and into tissues
• Need to resurface slowly to allow N time to come out of blood at lungs and be breathed out
• If resurface too quickly then N comes out as bubbles in blood
• Can block small capillaries and arteries leading to necrosis