Other Disorders Associated with Sleep-Disordered Breathing

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About 5% of OSA patients have chronic alveolar hypoventilation with elevated arterial carbon dioxide tension while awake (see Fig. 67-4). These patients have the so-called pickwickian or obesity-hypoventilation syndrome (OHS). They tend to be morbidly obese and have severe OSA with cor pulmonale and, in some cases, polycythemia. Although the pathophysiology of OHS remains poorly understood, daytime hypoventilation often resolves after effective treatment of the obstructive breathing events during sleep. Some OHS patients respond to nasal CPAP, but some require noninvasive mechanical ventilation, which provides augmented inspiratory pressure support.

Central sleep apnea (CSA) is not common. Central apneas result from an instability in the ventilatory control system. Congestive heart failure is the most common cause of CSA. Patients with neurologic disorders involving brain stem respiratory control centers may have CSA. The clinical sequelae of CSA are similar to those described for OSA. Supplemental oxygen, acetazolamide, or noninvasive nocturnal mechanical ventilation may help some patients.

Many patients with compromised pulmonary function (emphysema, kyphoscoliosis, respiratory muscle weakness) develop nocturnal oxygen desaturation from a combination of sleep-induced hypoventilation, reduced lung volumes, and ventilation-perfusion mismatching. These patients may benefit from assessment of the severity of nocturnal hypoventilation and the response to therapy. Therapy may involve optimizing pulmonary function, supplemental oxygen, or noninvasive nocturnal mechanical ventilation.

Bibliography

American Sleep Disorders Association: The international classification of sleep disorders: diagnostic and coding manual, Lawrence, KS, 1990, Allen Press.

American Thoracic Society Consensus Conference: Indications and standards for cardiopulmonary sleep studies, Am Rev Respir Dis 139:559, 1989.

Engleman HM et al: Effect of continuous positive airway pressure on daytime function in sleep apnoea/hypopnea syndrome, Lancet 343:572, 1994.

Hla KM et al: Sleep apnea and hypertension, Ann Intern Med 120:382, 1994.

Kryger MH: Management of obstructive sleep apnea, Clin Chest Med 13(3):481, 1992.

Sullivan CE et al: Reversal of obstructive sleep apnoea by continuous positive airway pressure applied through the nares, Lancet 1:862, 1981.

Wiegand L et al: Obstructive sleep apnea, Dis Month 40:197, 1994.

Young T et al: The occurrence of sleep-disordered breathing among middle-aged adults, N Engl J Med 328:1230, 1993.

RELATED STORIES:
Adult Obstructive Sleep Apnea: Pathophysiology and Diagnosis   Who Requires Treatment?   Therapy for Obstructive Sleep Apnea   Diagnosis of Obstructive Sleep Apnea   Pathophysiology of Obstructive Sleep Apnea   Risk Factors for Obstructive Sleep Apnea   Definitions: Apnea and Hypopnea   Normal Sleep and Respiration   Consequences of Sleep-Disordered Breathing   Clinical Evaluation of potential Sleep Apnea patients

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