Lecture #21: Diffusion

Question 1

What are the 2 factors that affect the rate of diffusion?

aka make is harder

Answer 1

1. Thickness of the alveolus
2. The distance of the gap between the alveolus and the RBC

Question 2

What is the normal cardiac output?

Answer 2

5L/min

Question 3

How long is a normal person’s transit time?

Answer 3

0.75 seconds

Question 4

What is the required time to get PO2 from 40 to 100?

Answer 4

0.3 seconds

Question 5

What is the normal cardiac output given exercise?

Answer 5

25L/min

Question 6

True or False
When we exercise, we make the flow rate increase via our cardiac output, which means our transit time should decrease

Answer 6

True

Question 7

5L a minute is also known as what?

Answer 7

a flow rate

Question 8

What would the transit time be during exercise?

Answer 8

0.45

Question 8

Would we be okay during exercise if our transit time is 0.45?

Answer 8

Yes, because it only takes 0.3 sec to get from a PO2 of 40 to 100

Question 9

In a normal condition is a person’s PaO2 is less than 100 within the transit time. What can we deduce about them?

Answer 9

Hypoxemic

Question 10

Restrictive diseases are a form of what?

Answer 10

diffusion limitations

Question 11

What happens to diffusion when we have moderate diffusion limitation?

Answer 11

• takes the full 0.75 secs to get from a PO2 of 40 - 100
• At rest, they were not hypoxemic
• However, during exercise, when the transit time is 0.45, the PO2 will be around 80

Question 12

What is pulmonary edema?

Answer 12

gap widening, more interstitial fluid due to poor LV failure or post-MIocardial infarction

Question 13

What is pulmonary fibrosis?

Answer 13

thicker wall due to scar tissue from infection or inhalation of chemicals

Question 14

What happens to diffusion when we have severe diffusion limitation?

Answer 14

• At rest, they will have a PO2 of under 100, most likely 80

Question 15

True or False
CO2 has diffusion limitations as well; however, it moves faster and can diffuse more easily

Answer 15

True

Question 16

How long does it take for PCO2 to get from 40 to 46?

Answer 16

0.15 seconds

Question 17

What are 2 restrictive diseases that can lead to hypoxemia during exercise?

Answer 17

1. Pulmonary fibrosis
2. Pulmonary edema

Question 18

What is the difference between a restrictive disease and an obstructive disease

Answer 18

Restrictive disease = hard to get air in, hard to stretch the tissue to inflate the lung

Obstructive disease = hard to get air out

Question 19

What is compliance?

Answer 19

the ability to expand the lung in response to a difference in pressure

Question 20

What does Pulmonary Edema lead to?

Answer 20

POOR LV FUNCTION
- increase the left atrial pressure
- increases pulmonary venous pressure
- forces fluid from capillaries into the interstitial space
BACK UP OF FLUID - forcing fluid between the capillary and the alveoli, causing a bigger gap

Question 21

What happens to the lung compliance in both Pulmonary fibrosis and Pulmonary edema?

Answer 21

Lung Compliance is going down

Question 22

Laboured breathing is called what?

Answer 22

dyspenea

Question 23

What are the treatments for restrictive lung disease?

Answer 23

• Moderate program of physical activity to improve respiratory muscles and cardiac output
• Drugs are key to congestive heart failure

Question 24

What happens to PO2 during exercise?

Answer 24

Instead of going to the muscle at 100 and the muscle consuming 5, the mitochondria will consume more at the muscle, meaning we are coming out of the muscle with LESS than 40

Question 25

True or False During exercise, we increase our free ADP and our mitochondrial respiration

Answer 25

True

Question 26

What happens to PVO2 during exercise?

Answer 26

will decrease because the muscle is taking more O2 to around 20

Question 27

If we come in with a PVO2 of 20 (less), are we going to make it to 100?

Answer 27

- Yes - PaO2 will remain essentially constant even though the venous blood is coming in with lower amounts - This means the lung is doing a really good job, meaning the PAO2 will increase to keep the PaO2 constant - Ventilation goes up

Question 28

What happens to PVCO2 during exercise?

Answer 28

It will increase because of more aerobic metabolism - more Krebs cycle producing CO2 - extra CO2 from the buffering system

Question 29

What happens to PaCO2 during exercise?

Answer 29

Remain constant and can actually go down, due to the lung doing a good job at getting rid of the CO2 due to the increased Ventilation

Question 30

Does the lung limit our VO2 max?

Answer 30

Naurr

Question 31

Which 2 Partial pressures in the blood indicate the effectiveness of the lungs?

Answer 31

PAO2 - will make sure arterial O2 is remaining constant, so we are not hypoxic PaCO2 - steadies the CO2 levels to make sure we are not hypercapnic as the ventilation rate increases to get rid of the excess CO2

Question 32

True or False Really well-trained endurance athletes will be at a point of hypoxemia

Answer 32

True

Question 33

Why would well-trained endurance athletes have a disadvantage when it comes to oxygen transport and diffusion?

Answer 33

1. They have a higher cardiac output 2. They have a higher than normal Oxygen extraction due to having more mitochondria *This means they come in with PVO2 of 10-15, and they have a transit time of 0.25, so the intersection for the oxygen to saturate with Hb will be at 85 mmHg rather than 100, meaning they are technically hypoxemic

Question 34

What are the 2 ways oxygen is transported?

Answer 34

1. Dissolved in the blood 2. Bound to Hb

Question 35

What is the solubility constant of oxygen in the blood?

Answer 35

0.003 mL/100 mL of blood/mmHg

Question 36

Another way to say 0.3mls O2/100 mls of blood is?

Answer 36

0.3 vols %

Question 37

How many grams of Hb do males have per 100 ml of blood?

Answer 37

16 g

Question 38

How many grams of Hb do females have per 100 ml of blood?

Answer 38

14 g

Question 39

How much O2 can 1 gram of Hb hold?

Answer 39

1.34 mls of O2 *when 100 % saturated

Question 40

True or False The higher the PO2, the higher the HB saturation

Answer 40

True