Lecture 18: Oxygen and Carbon dioxide exchange

Question 1

What is respiratory minute volume?

Answer 1

The amount of air breathed in a minute

Question 2

How do you calculate respiratory minute volume?

Answer 2

Respiratory minute volume = tidal volume x Respiratory rate

Question 3

What is tidal volume determined by?

Answer 3

Breathing strength

Question 4

What is respiratory rate determined by?

Answer 4

Breathing speed

Question 5

What is the unit for respiratory minute volume?

Answer 5

L/min

Question 6

What is the unit for tidal volume?

Answer 6

L/breath

Question 7

What is the unit for respiratory rate?

Answer 7

Breaths/min

Question 8

What is dead space?

Answer 8

The air we breath in that doesn’t get to the alveoli so cannot go through gas exchange (air that can’t be used)

Question 9

What is the approximate amount of dead space regardless of breath type?

Answer 9

150 mls

Question 10

What is really important for breathing?

Answer 10

The amount of air that gets into the alveoli

Question 11

What is Alveolar ventilation?

Answer 11

The amount of air that gets into the alveoli

Question 12

How do you calculate alveolar ventilation?

Answer 12

(Tidal volume - Dead space) x Respiratory rate

Question 13

Are tiny rapid breaths helpful?

Answer 13

No, because of dead space

Question 14

What does gas diffusion depend on?

Answer 14

Partial pressures

Question 15

What is daltons law?

Answer 15

In a gas mixture (air), each gas exerts its own individual pressure, called a partial pressure (P)

Question 16

What does the pressure of a mixture of gases = ?

Answer 16

The sum total of the pressures of each individual gas

Question 17

What is the goal of gas movement in respiration?

Answer 17

Move gas back and forth between the alveoli and the capillaries

Question 18

Where do we want to transport inhaled air?

Answer 18

Into the capillaries

Question 19

Where do we want to transport carbon dioxide?

Answer 19

Into the alveoli to be exhaled

Question 20

What is Fick’s law of diffusion?

Answer 20

Gases move across the membranes between the alveoli and the capillaries by diffusion

Question 21

What determines the rate of diffusion according to Fick’s law?
(3)

Answer 21

• Surface area of the membranes
• Thickness of the membranes
• Pressure difference between the two sides

Question 22

What is Fick’s law equation?

Answer 22

F = (A/T) x d x (P1 - P2)

Question 23

What does F stand for in Ficks law of diffusion equation?

Answer 23

Flux (amount flowing)

Question 24

What does A stand for in Ficks law of diffusion equation?

Answer 24

Surface area

Question 25

What does T stand for in Ficks law of diffusion equation?

Answer 25

Thickness

Question 26

What does D stand for in Ficks law of diffusion equation?

Answer 26

Diffusion constant

Question 27

What does P1 - P2 stand for in Ficks law of diffusion equation?

Answer 27

Pressure difference

Question 28

What does the diffusion constant or coefficient for a substance depend on?

Answer 28

Gas solubility (S) and its molecular weight

Question 29

On a per molecule rate how much faster does Carbon dioxide diffuse than Oxygen?

Answer 29

20x due to carbon dioxide's higher solubility

Question 30

What does the bulbous structure of alveoli and the high density of capillaries do?

Answer 30

Create lots of surface area for gas exchange

Question 31

What is Emphysema?

Answer 31

A disease characterised by the dilation of the alveolar spaces and destruction of the alveolar walls

Question 32

What does a reduction in surface area mean for oxygen exchange?

Answer 32

It is greatly reduced as there is less contact between the air and capillaries

Question 33

What is the blood-air barrier mostly comprised of?

Answer 33

The alveolar and capillary walls

Question 34

What's is the distance between the alveolar air and the blood?

Answer 34

Small

Question 35

What is a result of Pulmonary fibrosis?

Answer 35

Thickening and scarring of the alveolar membranes

Question 36

What can cause Pulmonary fibrosis?

Answer 36

Chronic inflammation or exposure to industrial chemicals

Question 37

What is the main factor for gas transfer?

Answer 37

Pressure difference

Question 38

What does alveolar partial pressure of Oxygen depend on? | 3

Answer 38

- Partial pressure of oxygen in inspired air - Alveolar ventilation - Oxygen consumption - Blood oxygen

Question 39

What does alveolar partial pressure of carbon dioxide depend on? (3)

Answer 39

- partial pressure of carbon dioxide in inspired air - Alveolar ventilation - Carbon dioxide production

Question 40

Because Partial pressure of oxygen is usually constant, what is it the balance of that is most important in driving oxygen exchange?

Answer 40

Balance between oxygen consumption and alveolar ventilation

Question 41

Alveolar partial pressure of carbon dioxide is usually determined by what because atmospheric partial pressure of carbon dioxide is negligible?

Answer 41

Balance between carbon dioxide production and alveolar ventilation

Question 42

What do gasses diffuse down?

Answer 42

Their pressure gradients