Hypoventilation Syndromes and Congenital Hypoventilation Syndrome (CHHS)

Question 1

why is minute ventilation regulated?

think:
- artery gas and pH

Answer 1

to maintain arterial blood gases and stabilise pH

Question 2

what 3 things do chemoreceptors regulate regarding blood vessels

think:

• partial pressures and [H+] scale

Answer 2

• PaO2
• PaCO2
• pH

Question 3

what 3 things characterise chronic hypoventilation?

Answer 3

• reduced tidal volume and reduced breathing rate
• hypercapnia (elevated PaCO2)
• normal pH due to initiation of compensation mechanisms

Question 4

why is pH normal in chronic hypoventilation?

think: kidneys

Answer 4

kidneys retain bicarbonate, increasing bicarbonate levels

Question 5

what is a major characteristic of Type II respiratory failure

Answer 5

Hypercapnia (elevated PaCO2)

Question 6

what are 4 hypoventilation syndrome subtypes other than congenital central alveolar hypoventilation syndrome?

think:
- o
- i
- s due to m
- l

Answer 6

• obesity hypoventilation syndrome
• idiopathic chronic alveolar hypoventilation
• sleep-related hypoventilation due to medical conditions/pharmacological influence
• late onset central hypoventilation

Question 7

how is congenital central alveolar hypoventilation syndrome characterised?

think:

• respiratory drive and sleep

Answer 7

• failure of central respiratory drive associated with sleep

Question 8

congenital central hypoventilation Syndrome (CCHS)

mutations in what transcript factor cause CCHS

Answer 8

paired-like homebox 2B (PHOX2B) gene

Question 9

CCHS is an autosomal dominant disease. True or false?

Answer 9

True. CCHS is autosomal dominant

Question 10

what are 3 characteristics of CHHS

think:

Answer 10

• voluntary breating intact when awake, but automatic breathing is absent during sleep
• you only stay alive if you remember to breathe
• shallow breaths are taken

Question 11

what type of increased mutations in exon 3 of the PHO2B gene do majority of people with CCHS have and what do minority of people have?

Answer 11

Majority: increased Polyalanine repeat mutations (PARMs)

Minority: increased non polyalaniene repeat mutations (NPARMs)

Question 12

why do some people with CCHS need medication only at certain times (like sleep) and some people need ventilatory support both in the night and the day?

HINT:
- think about PARM/nPARMs

Answer 12

the more PARM/NPARM mutations someone with CHHS has, the more severe the dysfunction.

Thus, certain people need more support throughout the day due to increased PARM/NPARM mutuations.

Question 13

how do people with CCHS manage the absence of automatic breathing during sleep?

Answer 13

they are provided with mechanical ventilation or diaphragm pacing during sleep from the beginning of life

Question 14

outline 5 respiratory symptoms of CCHS

think:
- h
- o
- h & c
- g
- l

Answer 14

Respiratory:
- hypoventilation
- obstructive sleep apnea
- hypoxia & cyanosis
- gasping
- laboured breathing

Question 15

outline 3 cardiovascular symtoms of CCHS

think:
- b
- a
- i

Answer 15

• bradycardia/bradyarrythmia
• arrhythmias
• impaired BP during sleep

Question 16

what are 2 temperature instability symptoms of CCHS

think:
- t
- i

Answer 16

• trouble maintaining internal temperature of 37°C
• impairment of blood glucose metabolism

Question 17

what is 1 gastro-intestinal symptom of CCHS

think:
- H

Answer 17

• Hirschsprung disease

Question 18

what are 2 neurological symptom and 1 ophthalmologic symptom of CCHS

for neurological, think:
- s
- d

for opthalmologic, think:
- o

Answer 18

Neurological:
- seizures
- diffuse atrophy of astrocytes and glia in CNS

opthalmologic:
- occular dysfunction: can’t regulate pupil dilation

Question 19

what can diffuse atrophy of cells in CNS in CCHS lead to?

Answer 19

can lead to learning difficulties

Question 20

what type of cancers can arise from CCHS where do they originate?

Answer 20

• neuroblastomas
• originate in neural crest and found usually in sympathetic nervous system