Respiratory physiology 7

Question 1

The central chemoreceptor:
a. is located on the dorsal surface of the medulla
b. responds to PaCO2 and PaO2
c. is stimulated by pH changes in the cerebrospinal fluid
d. is acutely affected by bicarbonate in the serum

Answer 1

c. is stimulated by pH changes in the CSF

Question 2

The central chemoreceptors respond indirectly to

Answer 2

PaCO2

Question 3

Which of the following freely diffuse across the BBB?
CO2
H+
HCO3-

Answer 3

CO2

Question 4

After CO2 enters the CSF, it dissociates into

Answer 4

H+ & bicarb

Question 5

As H+ in the CSF rises, the rate and depth of respiration ______________

Answer 5

increase until a new minute ventilation steady state is achieved

Question 6

__________________ do not pass through the BBB

Answer 6

Non-volatile acids (such as lactic acid)

Question 7

Therapeutic hyperventilation (to reduce ICP) is only effective for

Answer 7

a few hours to ~ 2 days

Question 8

The central chemoreceptor is stimulated by

Answer 8

hypercarbia & hypoxemia
but it’s depressed by profound hypercarbia & hypoxemia

Question 9

The most important stimulus for the central chemoreceptor is

Answer 9

the hydrogen ion concentration in the CSF

Question 10

_____________ drives the respiratory pacemaker in the dorsal respiratory center

Answer 10

H+

Question 11

Select the statements that BEST describe the carotid chemoreceptors (Select 2.):
a. They are more sensitive to SaO2 than PaO2
b. Hering’s nerve is part of the afferent limb
c. They are more sensitive after carotid endarterectomy
d. Type 1 Glomus cells mediate hypoxic ventilatory drive

Answer 11

b. Hering’s nerve is part of the afferent limb
d. type 1 glomus cells mediate hypoxic ventilatory drive

Question 12

The peripheral chemoreceptors reside in

Answer 12

the carotid bodies at the bifurcation of the common carotid artery
also present in the transverse aortic arch

Question 13

The chief responsibility of the carotid body is to monitor

Answer 13

hypoxemia (PaO2 <60 mmHg)

Question 14

The carotid body does not respond to

Answer 14

SaO2 or CaO2

Question 15

Sub anesthetic doses of inhalation and intravenous anesthetics (0.1 MAC) depress

Answer 15

the hypoxic ventilatory drive (risk of hypoxemia in the PACU)

Question 16

Carotid endarterectomy severs the

Answer 16

afferent limb of the hypoxic ventilatory response- which is why we don’t do bilateral CEA

Question 17

Secondary responsibilities of the peripheral chemoreceptors include

Answer 17

monitoring PaCO2, H+, and perfusion pressure

Question 18

What is the response to hypoxemia?

Answer 18

1. PaO2 <60 mmHg closes the oxygen-sensitive K+ channels in Type 1 glomus cells
2. Raises RMP, opens, Ca2+ channels, increases neurotransmitter release
3. Action potential is propagated along Hering’s nerve–> glossopharyngeal nerve (CN9)
4. Afferent pathway terminates in the inspiratory center in the medulla
5. minute ventilation increases to restore PaO2

Question 19

Conditions that impair hypoxic ventilatory response include

Answer 19

CEA
sub-anesthetic doses of inhalation and IV anesthetics

Question 20

What conditions do not impair the hypoxic ventilatory response?

Answer 20

even though CaO2 is reduced with anemia as well as carbon monoxide poisoning, the PaO2 is usually normal which explains why they do not stimulate the hypoxic ventilatory response

Question 21

Which reflex prevents alveolar overdistension?
a. Hering-Breuer deflation reflex
b. paradoxical reflex of Head
c. Hering-Breuer inflation reflex
d. Pulmonary chemoreflex

Answer 21

c. Hering-Breuer inflation reflex

Question 22

_____________ in the smooth airway muscle in the lung influence respiratory pattern

Answer 22

Stretch receptors

Question 23

What is the role of the Hering-Breuer inflation reflex?

Answer 23

helps to avoid over-inflation
when lung hyperinflation turns off the respiratory drive

Question 24

What is the role of the Hering-Breuer deflation reflex?

Answer 24

activates the respiratory drive when lung volume is too small (helps to prevent atelectasis)

Question 25

What is the role of the J receptors (pulmonary C-fiber receptors)

Answer 25

increases the respiratory rate in the setting of pulmonary embolism or CHF

Question 26

What is the role of the paradoxical reflex of head?

Answer 26

causes a newborn baby to take their first breath

Question 27

Where do stretch receptors in the airway transmit their information?

Answer 27

along the vagus nerves (CN10) to the dorsal respiratory center (respiratory pacemaker)

Question 28

Is the Hering-Breuer inflation reflex active during normal inspiration?

Answer 28

No- it is active when lung inflation is >1.5 L above FRC (x3 normal Vt)

Question 29

Which agent is MOST likely to increase intrapulmonary shunt?
a. etomidate
b. ketamine
c. desflurane
d. propofol

Answer 29

c. Desflurane

Question 30

Hypoxic pulmonary vasoconstriction is a

Answer 30

local reaction that occurs in response to a reduction in alveolar oxygen tension (not arterial PO2)

Question 31

The goal of HPV is to

Answer 31

improve matching of ventilation & perfusion (to minimize shunt)

Question 32

The pulmonary vascular bed is the only region in the body that responds to hypoxia

Answer 32

with vasoconstriction

Question 33

HPV is inhibited by

Answer 33

volatile anesthetics >1.5 MAC
phosphodiesterase inhibitors
dobutamine
some calcium channel blockers
hypervolemia
excessive PEEP
large tidal volumes

Question 34

HPV is not inhibited by

Answer 34

IV anesthetics including ketamine, propofol, and opioids

Question 35

HPV is a protective mechanism that minimizes shunt flow during

Answer 35

atelectasis or one-lung ventilation