Institute for Continuing Education

Sleep-Related Hypoventilation/Hypoxemic Syndromes

Course Objectives

Upon successful completion of this module, you will be able to:

• Explain the pathophysiological mechanisms underlying sleep-related hypoventilation including alterations in respiratory control during sleep, reduced ventilatory responses to hypercapnia and hypoxemia, effects of sleep stage on respiratory muscle function, and the role of upper airway resistance in precipitating ventilatory failure.
• Classify sleep-related hypoventilation disorders according to the International Classification of Sleep Disorders, Third Edition (ICSD-3), distinguishing obesity hypoventilation syndrome, congenital central alveolar hypoventilation syndrome, sleep-related hypoventilation due to medication or substance use, sleep-related hypoventilation due to medical disorders (neuromuscular, chest wall, parenchymal lung disease), and idiopathic central alveolar hypoventilation.
• Identify clinical features, risk factors, and diagnostic criteria for obesity hypoventilation syndrome (OHS), understanding the epidemiology, the relationship between obesity and ventilatory failure, the overlap with obstructive sleep apnea, polysomnographic findings, and arterial blood gas abnormalities that distinguish OHS from uncomplicated obesity or OSA.
• Describe congenital central alveolar hypoventilation syndrome (CCHS) including genetic basis (PHOX2B mutations), clinical presentation in neonates and children, characteristic hypoventilation patterns during sleep and wakefulness, associated autonomic dysregulation, diagnostic evaluation, and long-term management with mechanical ventilation.
• Recognize sleep-related hypoventilation associated with neuromuscular disorders, chest wall disorders, and chronic lung disease, understanding how conditions including amyotrophic lateral sclerosis, muscular dystrophies, kyphoscoliosis, chronic obstructive pulmonary disease, and restrictive lung diseases produce nocturnal ventilatory failure preceding daytime respiratory insufficiency.
• Interpret polysomnographic findings diagnostic of sleep-related hypoventilation including sustained oxygen desaturation patterns, transcutaneous or end-tidal CO? monitoring demonstrating hypercapnia, characteristic breathing patterns across sleep stages, and distinguishing hypoventilation from obstructive or central apneas.
• Apply evidence-based therapeutic approaches for sleep-related hypoventilation disorders including positive airway pressure therapy (CPAP, bilevel PAP, volume-assured pressure support), weight loss and lifestyle interventions for obesity hypoventilation syndrome, invasive and non-invasive ventilation for neuromuscular and chest wall disorders, supplemental oxygen therapy considerations, and monitoring treatment efficacy through clinical, polysomnographic, and blood gas assessment.

Course Information

Sleep-induced hypoventilation is characterized by elevated levels of PaCO2 while asleep, defined in the ICSD-2 as a level > 45 mm Hg or “disproportionately increased relative to levels during wakefulness.” Sleep-induced hypoxemia in the ICSD-2 is defined as “an SpO2 [oxyhemoglobin saturation] during sleep of < 90% for more than five minutes with a nadir of at least 85%” or “> 30% of total sleep time with an SpO2 of < 90%.” Other sources define these gas exchange conditions differently, and the literature is sufficiently controversial in this regard that space limitations prevent any detailed discussion. Nocturnal hypoventilation can be attributed to either decreased ventilatory drive (“won’t breathe”) or worsening mechanics (“can’t breathe”). Nocturnal hypoxemia follows due to the displacement of oxygen in the alveoli from rising carbon dioxide levels, as predicted by the alveolar air equation. Alternatively, arterial hypoxemia alone may be the product of worsening ventilation/perfusion mismatch with greater effective shunt.