Normal Respiratory Physiology

Question 1

What is PaO2 at rest?

Answer 1

98mmHg

Question 2

What is PaCO2 at rest?

Answer 2

40mmHg

Question 3

What is PvO2 at rest?

Answer 3

40mmHg

Question 4

What is PvCO2 at rest?

Answer 4

46mmHg

Question 5

What is PAO2 at rest?

Answer 5

100mmHg

Question 6

What is PACO2 at rest?

Answer 6

40mmHg

Question 7

What is PiO2 at rest?

Answer 7

150mmHg

Question 8

What is PiCO2 at rest?

Answer 8

0mmHg

Question 9

What is arterial pH at rest?

Answer 9

7.38-7.42

Question 10

How much oxygen is supplied to the body per minute at rest?

Answer 10

250mLs

Question 11

How much carbon dioxide is removed from the body per minute at rest?

Answer 11

200mLs

Question 12

How much oxygen is supplied to the body per minute during exercise?

Answer 12

More than 4000mLs

Question 13

How much carbon dioxide is removed from the body per minute during exercise?

Answer 13

More than 4000mLs

Question 14

What is the difference between ventilation and gas exchange?

Answer 14

Ventilation is the air in and the air out, gas exchange is movement of gasses across the alveolar/capillary membrane

Question 15

What is the role of ventilation?

Answer 15

To maintain PAO2 and PACO2

Question 16

Are inspiration and expiration passive or active?

Answer 16

Inspiration is always active, expiration is passive at rest and active during exercise

Question 17

What is the role of the inspiratory muscles?

Answer 17

To generate a negative intrapleural pressure

Question 18

What are the inspiratory muscles?

Answer 18

diaphragm, external intercostals, sternocleidomastoids

Question 19

What are the expiratory muscles?

Answer 19

internal intercostals, abdominal muscles

Question 20

What is the tidal volume at rest?

Answer 20

500mLs

Question 21

What is the tidal volume during exercise?

Answer 21

Half of the VC

Question 22

What is the minute ventilation at rest?

Answer 22

7-8L/min

Question 23

What is the minute ventilation during exercise?

Answer 23

100L/min

Question 24

What is the total lung capacity?

Answer 24

The volume of air in the lungs at maximum inhalation - 5700mLs

Question 25

What is the residual volume?

Answer 25

The volume of air in the lungs at maximum exhalation - 1200mLs

Question 26

What is the vital capacity?

Answer 26

The difference between TLC and RV - 4500mLs

Question 27

What is the FEV1?

Answer 27

The forced expiratory volume in 1 second - approximately 80% of forced vital capacity

Question 28

What is the functional residual capacity?

Answer 28

The volume remaining after passive exhalation - 2200mLs

Question 29

What two forces must be overcome in inspiration?

Answer 29

Resistive (airflow through bronchi) and elastic (expansion of lungs and chest wall)

Question 30

What drives diffusion?

Answer 30

The difference in partial pressures of gasses on either side of the A-C membrane

Question 31

What determines the rate of diffusion?

Answer 31

Ficks law - where rate is directly proportional to the surface area and the difference in partial pressures and inversely proportional to the thickness of the membrane

Question 32

Why do carbon dioxide and oxygen have a different diffusion rate?

Answer 32

Because they have a different solubility and molecular weight so have a different constant in Ficks equation

Question 33

What is the difference in diffusion rate between carbon dioxide and oxygen?

Answer 33

The diffusion rate of carbon dioxide is 20 times that of oxygen

Question 34

How long does blood spend going past the alveoli at rest?

Answer 34

.75 seconds

Question 35

How long does diffusion of oxygen take at rest?

Answer 35

0.25 seconds

Question 36

What limits transfer of oxygen - diffusion or perfusion?

Answer 36

Perfusion (the amount of blood which goes past the alveoli)

Question 37

When does diffusion limit the transfer of oxygen?

Answer 37

If the A-C membrane is grossly abnormal - in disease states

Question 38

What is critical to efficient gas exchange?

Answer 38

Matching of ventilation and perfusion - most efficient when V/Q=1

Question 39

What happens if there is a low V/Q?

Answer 39

There is not enough ventilation for the rate of perfusion - will lead to hypoxia

Question 40

Where are the central chemoreceptors and what do they respond to?

Answer 40

Located on the ventrolateral medullary surface and respond to changes in H+ ions and CO2

Question 41

Where are the peripheral chemoreceptors and what do they respond to?

Answer 41

Located in the aortic arch and carotid bodies and respond to changes in H+, CO2 and O2

Question 42

Which has more effect on ventilation, carbon dioxide or oxygen partial pressures?

Answer 42

carbon dioxide

Question 43

What is the neural control of breathing?

Answer 43

Neurons in the dorsal respiratory group and ventral respiratory group in the medulla. The DRG communicates the input from receptors to the VRG. The VRG has inspiratory and expiratory parts. The inspiratory part sends signals along the phrenic and intercostal nerves to initiate contraction. The expiratory part stops the signal to allow for passive relaxation. There is also the pontine respiratory centre which modifies the VRG.

Question 44

What factors influence breathing?

Answer 44

Higher brain centres (voluntary control over breathing), pain and emotional stimuli acting through the hypothalamus, peripheral chemoreceptors, central chemoreceptors, stretch receptors in lung, irritant receptors in lung, receptors in muscles and joints

Question 45

Does haemoglobin use the same binding site for oxygen and carbon dioxide?

Answer 45

No - different receptors

Question 46

What are the three ways that carbon dioxide is carried in the blood?

Answer 46

Dissolved (10%), attached to proteins such as haemoglobin as carbamino compounds (30%), and as bicarbonate (60%) formed in RBCs by carbonic anhydrase

Question 47

How is blood pH maintained?

Answer 47

Through a buffer system through this equation --

Question 48

What happens when blood pH rises?

Answer 48

The respiratory centre is depressed so decreases ventilation so CO2 accumulates and the equation is pushed to the right

Question 49

What happens when blood pH drops?

Answer 49

The respiratory centre is activated so increases ventilation so CO2 drops and the equation is pushed to the left

Question 50

What is metabolic alkalosis?

Answer 50

When the blood pH is high and the respiratory system can’t compensate

Question 51

What is metabolic acidosis?

Answer 51

When the blood pH is low and the respiratory system can’t compensate

Question 52

What is respiratory acidosis?

Answer 52

Hypoventilation - when there is not enough ventilation so CO2 builds up and causes a decrease in blood pH

Question 53

What is respiratory alkalosis?

Answer 53

Hyperventilation - when there is too much ventilation so not enough CO2 which causes a high blood pH