pk1 Gas Laws and Ventilation

Question 1

How is metabolic rate measured?

Answer 1

O2 consumption rate or CO2 production rate.

Question 2

What is the average basal metabolic rate?

Answer 2

250ml/O2/min

Question 3

What is the daily average metabolic rate?

Answer 3

1000ml/O2/min

Question 4

What is the average metabolic rate during exercise?

Answer 4

Up to 3000ml/O2/min

Question 5

Which value relates the rate of consumption of O2 to the rate of production of CO2?

How is this value calculated?

Answer 5

RQ

Vco2/Vo2

Question 6

What is the RQ of carbohydrate?

Answer 6

1.0

Question 7

What is the RQ of protein?

Answer 7

0.81

Question 8

What is the RQ of fat?

Answer 8

0.7

Question 9

What is the RQ of a well balanced diet?

Answer 9

0.8

Question 10

What is the name given to generation 0?

Answer 10

Trachea.

Question 11

What is the name given to generation 10?

Answer 11

Small Bronchi.

Question 12

What is the name given to generation 14?

Answer 12

Bronchioles.

Question 13

What is the name given to generation 17?

Answer 13

Respiratory Bronchioles.

Question 14

What is the name given to generation 23?

Answer 14

Alveolar Sacs.

Question 15

What is the equation for flow?

Answer 15

V. = uA

V = Flow (cm^3/sec)
u = Gas Speed (cm/sec)
A = Total Area (cm^2)

Question 16

At which generation is gas exchange determined by diffusion rather than convection?

Answer 16

Generation 17.

Question 17

Why does gas exchange depend on diffusion rather than convection at late generations?

Answer 17

V. = uA

A becomes so large that u is down to the speed of molecular diffusion.

Question 18

Which generations comprise the conducting zone?

Which generations comprise the transitional and respiratory zones?

Answer 18

Conducting zone: 0-16

Transitional and respiratory zone: 17-23

Question 19

List 3 factors that affect the rate of diffusion of gases.

Answer 19

Partial pressure gradients.

Temperature

Diffusion distance

Question 20

What is Barometric pressure (Pb)?

Answer 20

The pressure exerted by the weight of gas molecules in the atmosphere above the point of measurement.

Question 21

What is atmospheric pressure at sea level?

Answer 21

100kPa

Question 22

How does atmospheric pressure change with altitude?

Answer 22

Atmospheric pressure decreases exponentially with altitude.

It halves every 5450m.

Question 23

Which two variables affect partial pressure?

Answer 23

1 - The number of molecules of that gas in the given volume.

2 - Temperature.

Question 24

What is the equation for total pressure?

Answer 24

P1 + P2 + P3 + … Pn

Where p = partial pressure of any individual gas.

Question 25

Calculate the total atmospheric pressure at sea level. Show the working.

Answer 25

Total pressure = PN2 + PO2 + PH2O + PCO2 Total pressure = 74 + 21 + 5 + 0 = 100kPa.

Question 26

What is the equation for partial pressure?

Answer 26

Partial pressure = Fractional Concentration * Total Pressure

Question 27

What is dead space?

Answer 27

The volume of gas within the respiratory system in which gas exchange does not occur. Occupied by the conducting zone.

Question 28

Why do we have a conducting zone?

Answer 28

It is a result of internalising the lungs.

Question 29

Why might alveolar dead space arise?

Answer 29

Because of respiratory diseases.

Question 30

What is the approximate volume of the anatomical dead space of the respiratory system in an adult male?

Answer 30

150ml

Question 31

In a healthy person, what is the alveolar dead space?

Answer 31

Normally 0ml.

Question 32

What is the physiological dead space?

Answer 32

Anatomic Dead Space + Alveolar Dead Space

Question 33

What is the main factor affecting anatomic dead space?

Answer 33

The size of the subject.

Question 34

List 2 diseases that can increase alveolar dead space due to under-perfusion of alveoli.

Answer 34

1 - Pulmonary hypotension. 2 - Pulmonary embolism.

Question 35

Why does increasing physiological dead space impact adversely on blood oxygenation?

Answer 35

Because increasing physiological dead space decreases alveolar ventilation. This is because air in the dead space does not reach the alveoli.

Question 36

What is the equation for minute ventilation?

Answer 36

V.e = Vt * f ``` Ve = Minute Ventilation Vt = Tidal Volume f = Respiratory Frequency (breaths/min) ```

Question 37

Why is alveolar (useful) ventilation different from minute ventilation?

Answer 37

Minute ventilation does not account for the volume of air that does not reach the respiratory zone.

Question 38

What is the equation for alveolar ventilation?

Answer 38

V.a = (Vt-Vd) x f ``` V.a = Alveolar Ventilation Vt = Tidal Volume Vd = Dead Space Volume f = Respiratory Frequency (breaths/min) ```