327.26 (647.36) Comorbid sleep-related hypoventilation: This subtype occurs as a consequence of a medical condition, such as a pulmonary disorder (e.g., interstitial lung disease, chronic obstructive pulmonary disease) or a neuromuscular or chest wall disorder (e.g., muscular dystrophies, postpolio syndrome, cervical spinal cord injury, kyphoscoliosis), or medications (e.g., benzodiazepines. opiates). It also occurs with obesity (obesity hypoventilation disorder). where it reflects a combination of increased work of breathing due to reduced chest wall compliance and ventilation-perfusion mis- match and variably reduced ventilatory drive. Such individuals usually are character- ized by body mass index of greater than 30 and hypercapnia during wakefulness (with a p002 of greater than 45), without other evidence of hypoventilation.
Specify current severity:
Severity is graded according to the degree of hypoxemia and hypercarbia present dur- ing sleep and evidence of end organ impairment due to these abnormalities (e.g., right- sided heart failure). The presence of blood gas abnormalities during wakefulness is an indicator of greater severity.
Regarding obesity hypoventilation disorder, the prevalence of obesity hypoventilation in the general population is not known but is thought to be increasing in association with the increased prevalence of obesity and extreme obesity.
Sleep-related hypoventilation can occur independently or, more frequently, comorbid with medical or neurological disorders, medication use, or substance use disorder. Al- though symptoms are not mandatory to make this diagnosis, individuals often report excessive daytime sleepiness, frequent arousals and awakenings during sleep, morning headaches, and insomnia complaints.
Individuals with sleep—related hypoventilation can present with sleep-related complaints of insomnia or sleepiness. Episodes of orthopnea can occur in individuals with diaphragm weakness. Headaches upon awakening may be present. During sleep, episodes of shallow breathing may be observed, and obstructive sleep apnea hypopnea or central sleep apnea may coexist. Consequences of ventilatory insufficiency, including pulmonary hyperten- sion, cor pulmonale (right heart failure), polycythemia, and neurocognitive dysfunction, can be present. With progression of ventilatory insufficiency, blood gas abnormalities ex- tend into wakefulness. Features of the medical condition causing sleep-related hypoven- tilation can also be present. Episodes of hypoventilation may be associated with frequent arousals or bradytachycardia. Individuals may complain of excessive sleepiness and in- somnia or morning headaches or may present with findings of neurocognitive dysfunction or depression. Hypoventilation may not be present during wakefulness.
Idiopathic sleep-related hypoventilation in adults is very uncommon. The prevalence of congenital central alveolar hypoventilation is unknown, but the disorder is rare. Comor- bid sleep-related hypoventilation (i.e., hypoventilation comorbid with other conditions, such as chronic obstructive pulmonary disease [COPD], neuromuscular disorders, or obe- sity) is more common.
Idiopathic sleep-related hypoventilation is thought to be a slowly progressive disorder of respiratory impairment. When this disorder occurs comorbidly with other disorders (e.g.,
COPD, neuromuscular disorders, obesity), disease severity reﬂects the severity of the un- derlying condition, and the disorder progresses as the condition worsens. Complications such as pulmonary hypertension, cor pulmonale, cardiac dysrhythmias, polycythemia, neurocognitive dysfunction, and worsening respiratory failure can develop with increas- ing severity of blood gas abnormalities.