4. Alveolar Ventilation vs Pulmonary Ventilation

Question 1

What is anatomical dead space ?

Answer 1

Volume of gas occupied by the conducting airways and this gas is not available for exchange- 150ml

Question 2

What is pulmonary (minute) ventilation ?

Answer 2

total air movement into/out of lungs

Question 3

What is alveolar ventilation ?

Answer 3

Fresh air getting to alveoli and therefore available for gas exchange

Question 4

How is total pulmonary ventilation calculated ?

Answer 4

TPV= TV X RR

Question 5

How is air to alveoli calculated ?

Answer 5

Tidal - dead space

Question 6

How is alveolar ventilation calculated ?

Answer 6

AV= ait to alveoli X RR

Question 7

Will tidal volume be lower or higher when someone is anxious ?

Answer 7

Lower but respiratory rate increases

Question 8

Will tidal volume be lower or higher when someone is chilled out and relaxing ?

Answer 8

Higher but respiratory rate decreases

Question 9

What is the main factor that affects the alveolar ventilation ?

Answer 9

The depth of the breath, rather than the respiratory rate, because of the influence of the dead space volume

Question 10

What is hyperventilation ?

Answer 10

Increased ventilation - concerns depth and not frequency of breathingRelaxed is hyperventilating

Question 11

What is hypoventilation ?

Answer 11

Decreased ventilation - concerns depth and not frequency of breathinganxious is hypoventilation

Question 12

What is partial pressure ?

Answer 12

Pressure of a gas in a mixture of gases is equivalent to the percentage of that particular gas in the entire mixture multiplied by the pressure of the whole gaseous mixture

Question 13

for example if:Atmospheric pressure = 760mmHgPressure of air we breath therefore= 760mmHg21% of air we breath= O2What is the partial pressure of air we breath in ?

Answer 13

= 21% X 760mmHg = 160mmHg

Question 14

Once air is in alveoli what is it in equilibrium with ?

Answer 14

in equilibrium with the gas that’s in the blood

Question 15

How is air diluted ?

Answer 15

By dead space, residual volume and adding water vapour

Question 16

Is partial pressure of O2 in alveoli higher or lower than partial pressure of O2 in the air we breath ?

Answer 16

LowerAs air is diluted

Question 17

What is atmospheric pressure ?

Answer 17

760mmHg (101kPa)

Question 18

What is normal alveolar ventilation ?

Answer 18

4.2L/min

Question 19

What is the fluctuation of PO2 and PCO2 like under normal resting conditions ?

Answer 19

PO2 and PCO2 remain fairly constant

Question 20

What happens to PO2 and PCO2 during hyper-ventilation (increased alveolar ventilation) ?

Answer 20

PO2 rises to about 120 mm Hg and PCO2 falls to about 20 mmHg

Question 21

What happens to PO2 and PCO2 during hypo-ventilation (decreased alveolar ventilation) ?

Answer 21

PO2 falls to 30mmHg and PCO2 rises to 100mmHg

Question 22

What is normal alveolar partial pressure ( systemic arterial PP) of O2 ?

Answer 22

100mmHg (13.3kPa)

Question 23

What is normal alveolar pressure (systemic arterial PP) of CO2 ?

Answer 23

40mmHg (5.3kPa)

Question 24

Which part of the lung changes more significantly in volume when the pressure increases ?

Answer 24

The base, the volume change is much greater for a given change in pressure

Question 25

What is the relationship between height from base to apex and alveolar ventilation?

Answer 25

Alveolar ventilation declines with height from base to apex

Question 26

When is compliance lower ?

Answer 26

At the apex due to being more inflated at FRC, at the base the lungs are slightly compressed by the diaphragm hence more compliant on inspiration