Sleep-related breathing disorders

Question 1

What are hypoventilation syndromes?

Answer 1

• primary alveolar hypoventilation: idiopathic
• obesity-hypoventilation syndrome (Pickwickian syndrome)
• respiratory neuromuscular disorders

Question 2

What is Pickwickian syndrome?

Answer 2

obesity-hypoventilation syndrome

Question 3

What is sleep apnoea?

Answer 3

• episodic decreases in airflow during sleep
• quantitatively measured by the Apnea/Hypopnea Index (AHI) = # of apneic and hypopneic
events per hour of sleep
• sleep apnea generally accepted to be present if AHI >15

Question 4

How is breathing different during sleep?

Answer 4

• Tidal volume decreases
• Arterial CO2 increases (due to decreased minute ventilation)
• Pharyngeal dilator muscles relax
causing increased upper airway resistance

Question 5

What is apnoea & hypopnea?

Answer 5

Apnea: absence of breathing for ≥10 s.

Hypopnea: excessive decrease in rate or depth of breathing (>50% reduction in ventilation).

Question 6

What are the (3) classifications of sleep apnoea?

Answer 6

1. obstructive (temporary obstruction of upper airway)
2. central (temporary decrease in CNS drive to breathe)
3. mixed (features of both OSA + CSA)

Question 7

Describe obstructive sleep apnoea

Answer 7

ƒƒ- caused by transient, episodic obstruction of the upper airway
ƒƒ- absent or reduced airflow despite persistent respiratory effort
- due to: obesity, upper airway abnormality, neuromuscular disease, hypothyroidism,
alcohol/sedative use, nasal congestion, sleep deprivation

Question 8

Describe central sleep apnoea

Answer 8

ƒƒ- caused by transient, episodic decreases in CNS drive to breathe
- ƒƒno airflow because no respiratory effort
ƒƒ- Cheyne-Stokes Respiration

Question 9

What is Cheyne-Stokes respiration?

Answer 9

a form of CSA in which central apneas alternate with hyperpneas to produce a crescendo-decrescendo pattern of tidal volume; seen in severe LV dysfunction, brain injury, and other settings

Question 10

Describe mixed sleep apnoea

Answer 10

ƒƒ- features of both OSA and CSA
ƒƒ- loss of hypoxic and hypercapnic drives to breathe secondary to “resuscitative breathing”:
overcompensatory hyperventilation upon awakening from OSA induced hypoxia

Question 11

Px of sleep apnoea

Answer 11

• obtain history from spouse/partner
• secondary to repeated arousals and fragmentation of sleep: daytime somnolence, personality
and cognitive changes, snoring
• secondary to hypoxemia and hypercapnia: morning headache, polycythemia, pulmonary/
systemic HTN, cor pulmonale/CHF, nocturnal angina, arrhythmias
• the typical presentation for OSA is a middle-aged obese male who snores
• CSA can be due to neurological disease

Question 12

What are the indications for a sleep study (polysomnography)?

Answer 12

• ŠŠexcessive daytime sleepiness
• ŠŠunexplained pulmonary HTN or polycythemia
• ŠŠdaytime hypercapnia
  ŠŠ- titration of optimal nasal CPAP
• ŠŠassessment of objective response to other interventions

Question 13

Rx of sleep apnoea

Answer 13

• modifiable factors: weight loss, decreased alcohol/sedatives, nasal decongestion, treatment of
underlying medical conditions
• OSA or MSA: nasal CPAP, postural therapy (i.e. no supine sleeping), dental appliance,
uvulopalatopharyngoplasty, tonsillectomy
• CSA or hypoventilation syndromes: nasal BiPAP/CPAP, respiratory stimulants (e.g. progesterone) in select cases
• tracheostomy rarely required and should be used as last resort for OSA

Question 14

Cx of sleep apnoea

Answer 14

depression, weight gain, decreased quality of life, workplace and vehicular accidents, cardiac
complications (e.g. HTN), reduced work/social function

Question 15

How is CPAP beneficial in OSA?

Answer 15

• reduce CV risk

- reduce CV related deaths