Lecture 16 - Resp physiology Part 3

Question 1

Volume of single breath = ?
Breathing rate = ?
Total (mouth) ventilation = ?

Answer 1

-

Question 2

Pulmonary ventilation (VE) = ? x ?

Answer 2

-

Question 3

Dead space - what is it? How much?

Answer 3

Some of inhaled air never gets to alveoli so cannot gas exchange - known as DEAD SPACE (Vo) about 150mls

Question 4

Alveolar ventilation (VA) = ? x ?

What is it?
Low VA = ?
Extra VA = ?

Answer 4

f x (VT - dead space)

Measures the flow of fresh gases into and out of the alveoli

Low = hypOventilation
Extra = hypERventilation

Question 5

Slow, deep breathing increases/decreases VA?

Rapid, shallow breathing increases/decreases VA?

So is it correct to say that rapid breathing is hyperventilating?

Answer 5

Increases (Hyper)

Decreases (HYPOVENTILATION)

No

Question 6

Oxygen cascade

Pressure of O2 increases or decreases as it goes from atmosphere to mitochondria?

Answer 6

Decreases

Question 7

1. How much is O2 consumption (VO2)
2. Does O2 consumption increase or decrease with exercise and up to what?
3. How much CO2 production?
4. Can increase how much with exercise due to a____ m_____
5. VCO2/VO2 is known as what and what is commonly used?

Answer 7

1. 250 - 300ml/min
2. 4L/min
3. 200 - 250ml/min
4. > 5L/min
5. 200/250 = 0.8 commonly used (Respiratory exchange ratio, R)

Question 8

Fick’s law of diffusion - what is the formula?

What is the driving force?
How thick is blood-gas barrier?

Answer 8

F = (A/T)D(P1 - P2)
(flux/flow)

P1 - P2 (pressure difference)

0.3micrometes

Question 9

What is the D in the formula? - what does it depend on?

How much faster is CO2 at diffusing?

Answer 9

Diffusion constant (or coefficient for substance) depends on gas solubility and its molecular weight (Grahams Law)

20x

Question 10

What is Emphysema? How does it relate to Fick’s law?

Answer 10

It’s a disease characterised by dilation of the alveolar space and destruction of the alveolar walls (elastic tissue destroyed)

Decrease A so decrease PO2 in blood

Question 11

What is pulmonary fibrosis and how does it relate to fick’s law?

Answer 11

Involves the thickening and scarring of the alveolar membranes - can arise from chronic inflammation, drugs, industrial chemicals

Increase in thickness so decrease PO2

Question 12

What’s the main factor for diffusion? Give relative pressures plz

Answer 12

Pressure difference drives diffusion

PAO2 > PaO2

PACO2

Question 13

PAO2 and PACO2

-Set the alveolar “end” of the partial pressure diffusion gradient

These partial pressures are determined by:

1. _____ of inspired air
2. _____ ventilation
3. O2 ____ or CO2 _____
4. The maths of it all (matching of alveolar ventilation to _____ _____ blood flow)

Answer 13

1. Consumption
2. Alveolar
3. Consumption and production
4. Pulmonary capillary

Question 14

PAO2 is roughly how much compared to PB? Why?

What three things does it depend on?

Since atmospheric PO2 is relatively constant, the balance between what is most important?

Answer 14

1. 100mmHg and atmosphere is 159 - drops because dilution by water vapour and C02 in alveoli
2. PlO2 of inspired air (pressure of O2 in inhaled air)
   - VA = alveolar ventilation (f x VT - dead space)
   - Oxygen consumption (VO2)
3. Oxygen consumption and alveolar ventilation

Question 15

PACO2 is kept constant at ____mmHg

What three things does it depend on?

Since atmospheric CO2 is negligible - alveolar PCO2 is determined usually by what?

Answer 15

1. 40
2. PlCO2 of inspired air (pressure of CO2 in inhaled air)
   - VA = alveolar ventilation (f x VT - dead space)
   - CO2 production (VCO2)
3. Balance between production and ventilation

Question 16

What is the PaO2 and what is the PaCO2? Does the Pa every reach 100?

Answer 16

95mmHg and 40mmHg

No because O2 transfer not complete and some venous blood returns to the arteries without being oxygenated

Question 17

What is PvO2? What is PvCO2?

Answer 17

40 and 46