B2 Physiology of Respiration

Question 1

What is the term for the extent of elastic recoil during respiration (i.e. volume at expiration depending on what it was at inspiration)?

Answer 1

Hysteresis

Question 2

What is hysteresis?

Answer 2

The idea that the volume that the lungs decrease by at expiration depends on how much they increased on inspiration

Question 3

What three factors does lung stiffness depend on?

Answer 3

1. Elasticity of lung tissue
2. Surface Tension
3. Role of Surfactant

Question 4

What are the problems with having high surface tension in the alveoli?

Answer 4

a) high stiffness (low compliance)
b) alveolar instability, with small alveoli emptying into large alveoli; can cause atelectasis
c) movement of interstitial fluid into the alveoli (life threatening!)

Question 5

What is the relationship between surface tension and surfactant?

Answer 5

Surfactant reduces alveolar surface tension

Question 6

What is atelectasis?

Answer 6

Alveolar collapse

Question 7

How is ventilation measured?

Answer 7

Litres/ Minute

Question 8

What is tidal volume?

Answer 8

The volume of each breath

Question 9

What is vital capacity?

Answer 9

Volume of maximum expiration following maximum inspiration

Question 10

What is residual volume?

Answer 10

Air remaining in lungs after maximal expiration

Question 11

What is inspiratory reserve volume?

Answer 11

Vital capacity - expiratory reserve volume

Question 12

What is expiratory reserve volume?

Answer 12

Vital capacity - inspiratory reserve volume

Question 13

True or false? residual volume can be measured by spirometry?

Answer 13

False

Question 14

True or false? functional residual capacity can be measured by spirometry?

Answer 14

False

Question 15

How is residual volume measured?

Answer 15

Helium dilution method

Question 16

What does PEFR stand for?

Answer 16

Peak expiratory flow rate

Question 17

How is PEFR measured

Answer 17

Mini peak flow meters

Question 18

What is PEFR

Answer 18

The maximum flow at the outset of forced expiration

Question 19

Why is PEFR measured in asthma and COPD patients?

Answer 19

Forced expiration would be reduced in proportion to the severity of airway obstuction; can monitor effects of drugs

Question 20

How is carbon dioxide carried in the blood?

Answer 20

7% dissolved
70% HCO3
23% As carbamino compounds

Question 21

What is the Haldane effect?

Answer 21

CO2 reacts more with deoxygenated Hb than oxygenated Hb
Deoxygenated Hb is less acidic so accepts more H+
This means that deoxygenation increases the CO2 carrying power of blood

Question 22

Does the Haldane effect occur in the lungs?

Answer 22

No, the reverse reaction occurs

Oxygenation will decrease the CO2 carrying ability of blood, releasing it

Question 23

What effect does expiring CO2 have on pH?

Answer 23

Decreases H+ -Increasing pH

Question 24

What effect does inspiring CO2 have on pH?

Answer 24

Increases H+- Decreases pH

Question 25

True or false? Ventilation is sensitive to PO2?

Answer 25

False. It's sensitive to PCO2

Question 26

What does hyperventilation cause?

Answer 26

Alkalosis

Question 27

What is hyperventilation usually a result of?

Answer 27

Acidosis

Question 28

Why does hyperventilation cause alkalosis?

Answer 28

Lungs lose excess CO2 HCO3 falls so pH rises Kidney compensates by retaining H+ and excreting HCO3 pH is closer to normal but you've lost CO2 and HCO3

Question 29

What do low partial pressures of oxygen cause?

Answer 29

Hypoxic sensitive ventilation

Question 30

Why does hypoventilation cause acidosis?

Answer 30

Lungs keep the CO2 HCO3 rises so pH falls Kidney compensates by keeping HCO3 and getting rid of H+ pH is closer to normal but CO2 and HCO3 are high

Question 31

What is a metabolic cause of alkalosis?

Answer 31

Vomiting

Question 32

What are metabolic causes of acidosis?

Answer 32

DKA and Renal failure

Question 33

What are the body's responses to pH changes?

Answer 33

Buffering - HCO3 - rapid but limited Changes in ventilation - rapid but impossible if the cause is respiratory Kidney compensation - Slow but limited if the problem is kidney failure

Question 34

Are dead space and residual volume the same?

Answer 34

No

Question 35

What is dead space?

Answer 35

The volume of the lung that isn't available for gas exchange

Question 36

What is anatomical dead space?

Answer 36

The conducting respiratory system that don't take part in gas exchange anyway (about 150ml)

Question 37

What is physiological dead space?

Answer 37

Anatomical, plus the alveoli that will get air but don't have enough of a blood supply (about 150ml)

Question 38

What type of V/Q ratio will alveoli with an insufficient blood supply have?

Answer 38

Increased/ >1

Question 39

What is P50?

Answer 39

PO2 at 50% saturation of Hb (Normally about 27mm Hg)