Pulmonary Sleep Disorders

Question 1

sleep apnea

Answer 1

*repeated cessation of breath > 10 seconds during sleep → disrupted sleep → daytime somnolence
*diagnosis confirmed by sleep study
*nocturnal hypoxia → systemic and pulmonary hypertension, arrhythmias (atrial fibrillation/flutter), sudden death
*hypoxia → increased EPO release → increased erythropoiesesis
*several types: obstructive sleep apnea (OSA) central sleep apnea, hypoventilation syndromes

Question 2

obstructive sleep apnea (OSA) - overview

Answer 2

*a sleep order characterized by:
-MECHANICAL OBSTRUCTION of the upper airway
-repetitive cessation in respiration when sleeping
-repetitive disruptions in sleep (frequent awakenings) known as MICROAROUSALS
-daytime fatigue & sleepiness

Question 3

obstructive sleep apnea (OSA) - risk factors

Answer 3

*age
*obesity
*male gender
*craniofacial and upper airway abnormalities
*disorders of the CNS
*medications (respiratory depression)

Question 4

obstructive sleep apnea (OSA) - signs and symptoms

Answer 4

*hypertension
*obesity
*large neck circumference
*crowded oropharynx
*micrognathia
*snoring
*morning headaches
*difficulty staying sleep
*daytime sleeping

Question 5

obstructive sleep apnea (OSA) - diagnosis

Answer 5

*CBC demonstrating polycythemia in severe cases
*in-home apnea testing
*in-lab polysomnogram (GOLD STANDARD)
*diagnostic criteria:
-15 obstructive apnea episodes per hour
OR
-5 obstructive apnea episodes per hour with snoring or pauses in breathing and associated daytime symptoms

Question 6

obstructive sleep apnea (OSA) - treatments

Answer 6

*weight loss
*exercise
*abstain from alcohol & respiratory depressants
*oral surgery/dental devices
*continuous positive airway pressure (CPAP)
*surgery

Question 7

obstructive sleep apnea (OSA) - complications

Answer 7

*arrhythmias (ventricular tachycardia, bradycardia, stroke)
*daytime fatigue
*pulmonary hypertension
*right ventricular failure (cor pulmonale)
*type 2 diabetes
*CAD
*stroke

Question 8

central sleep apnea - overview

Answer 8

*increased number of apneas due to LACK OF RESPIRATORY DRIVE (vs. functional obstruction seen in OSA)
*can be sporadic or cyclical
*may be associated with Cheyne-Stokes respirations
*associated with: insomnia, age, comorbid conditions, nocturnal chest pain, daytime sleepiness

Question 9

central sleep apnea - etiologies

Answer 9

*stroke
*heart failure
*CNS injury/toxicity
*opioids

Question 10

Cheyne-Stokes breathing

Answer 10

*seen in patients with: heart failure; strokes
*characterized by HYPERVENTILATION (decreasing CO2) followed by APNEA & HYPOVENTILATION (increasing CO2)
*“crescendo-decrescendo” pattern
*note - can be seen in central sleep apnea

Question 11

central sleep apnea - treatment

Answer 11

*correct or treat underlying disorder
*CPAP + BiPAP

Question 12

hypoventilation syndromes - examples

Answer 12

1. obesity hypoventilation syndrome
2. hypoventilation due to COPD
3. neuromuscular
4. chest wall abnormalities (kyphoscoliosis, post thoracoplasty, etc)
5. hypoventilation due to underlying parenchymal or vascular disease

Question 13

hypoventilation syndromes - general pathophysiology

Answer 13

*2 mechanisms can lead to hypoventilation:
1) DECREASED ALVEOLAR MINUTE VENTILATION
2) INCREASED Vd/Vt (increased dead space)

Question 14

obesity hypoventilation syndrome - overview

Answer 14

*aka Pickwickian syndrome
*characterized by:
-obesity (BMI > 30)
-awake and nocturnal hypoventilation and hypoxemia
-sleepiness
-polycythemia
-Cor Pulmonale
*highly associated with OSA

Question 15

obesity hypoventilation syndrome - diagnosis

Answer 15

*ABG: hypoventilation (PCO2 > 45 mmHg)
*obesity (BMI > 30)
*lack of other etiology of hypoventilation (such as COPD)
*polysomnogram to diagnose confounding OSA

Question 16

obesity hypoventilation syndrome - pathophysiology

Answer 16

*obesity → hypoventilation → increased PaCO2 during waking hours → decreased PaO2 and increased PaCO2 during sleep
*adipose tissue leads to a “mass load” on the chest wall, causing increased work of breathing and LOWER LUNG COMPLIANCE

Question 17

obesity hypoventilation syndrome - treatment

Answer 17

*CPAP in selected patients
*BiPAP
*advanced non-invasive positive airway pressure therapy
*weight loss

Question 18

hypoventilation due to COPD - diagnosis

Answer 18

*history of COPD (chronic bronchitis or emphysema) [note - this occurs in SEVERE cases, not mild]
*ABG: hypercapnia & hypoxemia
*polysomnogram to diagnose concomitant OSA

Question 19

hypoventilation due to COPD - pathophysiology

Answer 19

*progressive FEV1 decline, air trapping → less capacity to maintain alveolar minute ventilation
*associated with progressive muscle weakness
*INCREASED Vd/Vt ratio (dead space ratio) due to:
-reduced alveolar minute ventilation → rapid shallow breathing
-air trapping
-emphysema
*OSA syndrome often present

Question 20

hypoventilation due to COPD - treatment

Answer 20

*treat underlying COPD (helps decrease air trapping, maximize FEV1, prevent exacerbations)
*BiPAP to improve ventilation

Question 21

hypoventilation-neuromuscular disorders - examples

Answer 21

*Guillain-Barre syndrome
*ALS
*acute polymyositis
*spinal cord traum
*etc
*overall: SYMPTOMS OF NM DISORDER + hypoventilation syndrome

Question 22

hypoventilation-neuromuscular disorders - pathophysiology

Answer 22

*common underlying mechanisms include:
-muscle weakness → “restrictive” physiology
-reduced alveolar minute ventilation
-INCREASED Vd/Vt ratio (dead space)

*exacerbating factors:
-recumbent position → diaphragm disadvantage
-REM sleep (skeletal muscle atonia)

Question 23

hypoventilation-neuromuscular disorders - diagnosis

Answer 23

*underlying NM disorder present
*ABG for morning hypercapnia
*PFTs:
-LOWER FVC in SUPINE position vs. UPRIGHT
-restrictive pattern
-low maximal voluntary ventilation
*low maximum inspiratory pressure
*low maximum expiratory pressure
*sniff test

Question 24

hypoventilation-neuromuscular disorders - treatment

Answer 24

*treat underlying NM disorder if possible
*non-invasive PAP (BiPAP)
*surgical tracheostomy with nocturnal or continuous mechanical ventilation