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Chapter 25. Management of Sleep-Related Breathing Disorders

A 38-year-old man presents with paroxysmal nocturnal dyspnea. He is experiencing progressive muscle weakness of the arms and legs secondary to amyotrophic lateral sclerosis. He also complains of early morning headaches lasting about 30 minutes. Pulmonary function testing shows an FVC = 48% of predicted and a maximum inspiratory pressure of –15 cm H2O. His resting awake arterial blood gases show pHa = 7.35, PaCO2 = 55 mm Hg, and PaO2 = 78 mm Hg. Use of an overnight earlobe pulse oximeter reveals sustained episodes of SaO2 <88% lasting 15 minutes. What is the most likely cause of his sleep-related breathing disorder?

a. Complex sleep apnea

b. Sleep-related hypoventilation/hypoxemic syndrome

c. Central sleep apnea

d. Cheyne-Stokes hypoventilation

e. Mixed sleep apnea

The most correct answer is b, the sleep-related hypoventilation/hypoxemic syndrome (SRH).

This patient has neuromuscular weakness (reduced FVC and MIP) due to amyotrophic lateral sclerosis, as well as hypercapnia (PaCO2 >45 mm Hg), and polysomnography that confirms sustained hypoxemia (SaO2 <90% for ≥5 minutes). These results are most consistent with secondary SRH due to neuromuscular disease.

A 75-year-old man is brought to the physician by his wife who witnessed frequent episodes of pauses in his breathing. She reports that the patient snores only mildly and intermittently. The patient's Epworth Sleepiness Scale score is at 12 [range: 0 (never sleepy) to 24 (very sleepy)] denoting mild hypersomnolence. His polysomnogram reveals frequent episodes of the event (double-headed arrow) seen below:


Which of the following conditions is most often associated with this event?

a. Congestive heart failure

b. Chronic obstructive pulmonary disease

c. Obesity

d. Severe kyphoscoliosis

e. Adenotonsillar hypertrophy

The most correct answer is a, congestive heart failure (CHF).

The polysomnogram depicts absent airflow accompanied by absent respiratory effort that are consistent with a central sleep apnea syndrome. CHF, chronic kidney disease, and cerebrovascular disease are medical conditions associated with central sleep apnea and/or Cheyne-Stokes breathing. Very severe COPD is associated with nocturnal hypoventilation and hypoxemia, especially worse during REM sleep. Chest wall abnormalities from morbid obesity and severe kyphoscoliosis can also result in sleep-related hypoventilation/hypoxemia. Adenotonsillar hypertrophy is the major cause of obstructive sleep apnea syndrome in children.


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