9 - Abnormal Ventilatory Control & Sleep Apnea

Question 1

What is the definition of apnea?

Answer 1

Complete lack of airflow for ≥ 10 seconds

Question 2

What is the definition of obstructive sleep apnea?

Answer 2

Symptoms + AHI ≥ 5/hr OR AHI ≥ 15/hr

Question 3

What are the risk factors for obstructive sleep apnea?

Answer 3

• increased age
• male
• obesity
• snoring
• craniofacial abnormalities
• nasal obstruction or redundant soft palate

Question 4

What causes obstructive sleep apnea?

Answer 4

Upper airway narrowing from fat deposition and decreased compensatory response by upper airway dilators to that narrowing (possibly due to leptin resistance)

Question 5

What are the clinical manifestations of obstructive sleep apnea?

Answer 5

• disturbed sleep
• daytime hypersomnolence
• morning headache
• nocturnal choking/resuscitative snort
• snoring
• non-restorative sleep
• insomnia
• inability to concentrate with reduced cognition
• altered mood, irritability
• decreased libido or impotence

Question 6

What are the complications of obstructive sleep apnea?

Answer 6

• hypertension
• cardiac problems
• stroke
• pulmonary hypertension
• poor performance in job/life
• car accidents
• depression
• GERD
• diabetes and insulin resistance (after prolonged OSA)

Question 7

How does obstructive sleep apnea affect morbidity and mortality?

Answer 7

• increases all cause mortality
• increases cardiovascular mortality
• increases risk for stroke

Question 8

What is the appearance of obstructive sleep apnea on polysomnography? What does central sleep apnea look like?

Answer 8

OSA - episodes of cessation of airflow despite continued respiratory effort

CSA - episodes of cessation of airflow without respiratory effort

Question 9

What is the differential diagnosis for obstructive sleep apnea?

Answer 9

• obesity hyperventilation syndrome (OHS)
• central sleep apnea (CSA)
• restless leg syndrome
• narcolepsy
• rotating shift worker/night worker
• GERD
• neuromuscular disease

Question 10

What should someone with obstructive sleep apnea avoid?

Answer 10

Sedatives and opiates (decrease the tone of the upper airway muscles and worsen airway collapse; also blunt respiratory drive)

Question 11

What are the treatment options for obstructive sleep apnea?

Answer 11

• CPAP (first line therapy, works to keep upper airway patent during sleep, effective in 70-80% patients)
• positional change (in mild cases)
• oral devices
• weight loss
• surgery (to remove some pharyngeal tissue)
• hypoglossal nerve stimulation device (for patients who are unresponsive to other treatments)

Question 12

What is the definition of obesity hyperventilation syndrome?

Answer 12

Obesity + daytime hypercapnia + no other explanation for increased PaCO2

Question 13

90% of patients with obesity hypoventilation syndrome also have ___.

Answer 13

Obstructive sleep apnea

Question 14

What PFT findings will be seen for a patient with obesity hypoventilation syndrome?

Answer 14

indications of restrictive disease with a normal A-a gradient

Question 15

What laboratory findings will be seen for a patient with obesity hypoventilation syndrome?

Answer 15

polycythemia from hypoxemia and increased bicarbonate from hypercapnia

Question 16

What are the pathophysiologic mechanisms that lead to hypoventilation in obesity hypoventilation syndrome?

Answer 16

Severe nocturnal hypercapnia causes significant CO2 accumulation, increased bicarbonate in response, and a blunted daytime response to increased PaCO2. Leptin resistance may play a role in hypoventilation/blunted respiratory drive.

Question 17

What are the treatment options for obesity hypoventilation syndrome?

Answer 17

• noninvasive ventilation
• weight loss
• avoid exacerbating agents
• pharmacologic treatment with respiratory stimulants (only addresses decreased respiratory drive but not other contributing factors)

Question 18

What is the definition of central sleep apnea?

Answer 18

Cessation of airflow without respiratory effort or markedly diminished respiratory effort

Question 19

What are the risk factors for central sleep apnea?

Answer 19

• increased age
• male
• heart failure
• atrial fibrillation
• stroke
• long acting opiates

Question 20

What sort of PFT results will a patient with obstructive sleep apnea have?

Answer 20

Normal PFTs (apnea only occurs when asleep)

Question 21

What is the pathophysiology mechanism that leads to central sleep apnea?

Answer 21

Most cases - An exaggerated response to increases and decreases in PaCO2 - CSA patient will hyperventilate excessively to relatively small increases in PaCO2, driving the PaCO2 down to a level that causes cessation of ventilation. PaCO2 then rises again, causing another cycle of hyperventilation and apnea; there may also be a severe narrowing of the upper airway, which contributes to the hyperventilatory response (due to increased effort needed to breathe)

Few cases - hypoventilation from lack of respiratory drive

Question 22

What is hypopnea?

Answer 22

≥ 30% decrease in airflow for ≥ 10 seconds PLUS decreased SpO2 of ≥ 3% OR arousal from sleep

Question 23

What is the apnea-hypopnea index (AHI)?

Answer 23

AHI = (apnea + hypopnea)/hour of sleep