20 Rhythmogenesis

Question 1

What is Locked in syndrome?

Answer 1

a patient with a brainstem stroke of the basilar artery is unable to move voluntarily

they have a regular breathing pattern driven by the metabolic system

Question 2

What is Ondine’s curse?

Answer 2

central hypoventilation syndrome
often in patients with medullary tumours
unable to sleep without mechanical ventilation
irregular breathing pattern when awake

driven by behavioural system

Question 3

What 2 types of systems do we consider with rhythmogenesis?

Answer 3

feeback

feedforward

Question 4

What are the 3 phases of neural rhythm in breathing?

Answer 4

1
P1
E-2

Question 5

In which phases of the neural rhythm cycle are the phrenic and internal intercostal nerves active?

Answer 5

phrenic nerve - 1 and P1, it’s most active between 1 and P1 tbh

IIN - E-2 and a bit of 1

Question 6

How does the diaphragm contract through the neural rhythm cycles?

Answer 6

1 - inspiratory ramp (contraction)

P1 - post-insp relaxation

Question 7

which parts of the neural rhythm cycle are inspiratory and expiratory?

Answer 7

1 - inspiratory

P1 and E2 - expiratory

Question 8

Name the 4 main respiratory groups in the brainstem

Answer 8

Pontine Respiratory Group
Botzinger complex
Dorsal Respiratory group
Ventral Respiratory Group

Question 9

What is the function of the NTS?

Answer 9

it receives information from sensory afferents, and stimulates inspiration via the DRG, PRG, Botz comp., and the VRG(i)

Question 10

What does the DRG do?

Answer 10

stimulates inspiration via the diaphragm and inhibits expiration in the VRG(e)

Question 11

What does thre PRG do?

Answer 11

influences the timing of breaths, controls both i and e

sitmulated by NTS, and has the capacity to stimulate and inhibit the DRG

Question 12

What does the Botz comp. do?

Answer 12

it is stimulated by the NTS, and inhibits inspiration through the DRG, and excites expiration through the VRG(e)

Question 13

When is the VRG(e) not active?

Answer 13

not active during resting breathing, or passive expiration

Question 14

What nerves do the VRG(i) and VRG(e) control?

Answer 14

VRG(i) - inspiratory accessory

VRG(e) - expiratory accessory

Question 15

What are the other controllers of ventilation?

Answer 15

higher centres, limbic and hypothalamus etc… (via DRG)

Cerebral cortex, voluntary control, straight to accessory nerves

Question 16

What 3 drugs act as respiratory stimulants?

Answer 16

Doxapram
Progesterone
Aminophylline

they increase VE and reduce PaCO2

Question 17

What diseases might respiratory stimulants be used to treat?

Answer 17

COPD
Obesity
Hypoventilation syndrome

Question 18

What happens to respiratory responsiveness in sleep?

Answer 18

decreased response to hypoxia, hypercapnia, and to mechanoreceptors

Question 19

What is OSA?

Answer 19

obstructive sleep apnoea

hypotonia of upper airways

Question 20

What is the effect of hypotonia of skeletal and respiratory muscles?

Answer 20

PaO2 and PaCO2 altered by up to 1kPa

Question 21

What drugs are associated with depressed ventilation?

Answer 21

inhalation anaesthetics
barbituates
opioids
benzodiazepines
alcohol

(they are all contraindicated with COPD)