Hypoventilation syndrome comprises disorders associated with alveolar hypoventilation (an elevation in PaCO₂ to levels >45 mmHg). Hypoxemia is also present in most cases, especially during sleep (PaO₂ <60 mmHg).
Alveolar hypoventilation can occur with obesity hypoventilation syndrome, restrictive thoracic disorders, central sleep apnea syndromes, and COPD.
Symptoms are often nonspecific, but almost always include disturbed sleep and impaired daytime function.
Physical exam often reveals signs of cor pulmonale in addition to those associated with the primary disorder.
Diagnosis is usually made by the clinician's awareness that alveolar hypoventilation is often associated with certain medical disorders. Investigations include arterial blood gas analysis, pulmonary function tests, measurement of respiratory muscle strength, and an overnight polysomnogram.
Treatment involves nocturnal ventilation, including the use of invasive ventilation.
Alveolar hypoventilation, defined as an elevation in PaCO₂ to levels >45 mmHg, can occur with several disorders: obesity hypoventilation syndrome, restrictive thoracic disorders, central sleep apnea syndromes, and COPD. These are referred to as the hypoventilation syndromes. Associated with hypercapnia is the development of hypoxemia, which adds to the clinical manifestations and morbidity. In addition, during sleep, hypoventilation becomes more profound and can worsen pre-existing hypercapnia and hypoxemia. In some cases, hypercapnia and hypoxemia may develop only during sleep, which may be unsuspected based on awake values.
History and exam
Other diagnostic factors
- male sex
- daytime sleepiness
- morning headache
- impaired cough
- repeated lower respiratory tract infections
- BMI ≥30 kg/m²
- increased pulmonic component of second heart sound (P2)
- lower-extremity edema
- right-sided third heart sound (S3 gallop)
- left-sided fourth heart sound (S4 gallop)
- body mass index (BMI) ≥30 kg/m²
- restrictive thoracic disorders
- central nervous system disorders
- obstructive airway disease
1st investigations to order
- arterial blood gas
- serum bicarbonate
- pulse oximetry
- hematocrit (Hct)
Investigations to consider
- pulmonary function tests
- respiratory muscle strength
- thyroid-stimulating hormone
- PHOX2B gene
obesity hypoventilation syndrome
restrictive thoracic disorders
- Interstitial lung disease
- Obstructive sleep apnea (OSA) without associated alveolar hypoventilation
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