MCQ's: Resp Physiology

Question 1

Chemoreceptors:

• location
• what do they detect and respond to

Answer 1

They are located in the carotid and aortic bodies.

Ventilation is predominantly controlled by central chemoreceptors in the medulla which respond to a rise in PaCO2 and CSF pH.

The carotid body is the prime O2 sensory organ.

Question 2

CO2 freely diffuses across BBB?

Answer 2

Yes, unlike H+ and bicarb

Question 3

CO2 binding to Hb is inhibited with increased O2 levels?

Answer 3

True.

By the Haldane effect oxygenated blood has a lower affinity for carbon dioxide, this is why in the lungs O2 displaces CO2 on the Hb and more CO2 is removed.

Question 4

How does PEEP affect collapsed alveoli?

Answer 4

It doesn’t open up collapsed alveoli, it just prevents alveoli from collapsing.

Question 5

Hyperventilation can lead to muscle spasm how?

Answer 5

Alkalosis, leads to less ionised calcium availability and therefore tetany.

Question 6

Carbon dioxide effect on blood vessel?

Answer 6

Hypercarbia causes vasodilation,

hypocarbia causes vasoconstriction.

Question 7

Hyperventilatory effect on CBF and CO?

Answer 7

Decreased CBF.

Hypercarbia causes an increase in cardiac output due to increased sympathetic activity.

BUT hypocarbia will reduce cardiac output from causing the direct vasoconstriction.

Question 8

In a spontaneously breathing patient in the lateral position, V/Q is greater in the dependant lung?

Answer 8

V/Q is < 1, ie there is a degree of shunt.

In areas of shunt alveolar gas tends toward mixed venous so PAO2 is low and PACO2 slighlty raised.