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At a glance

Acquired obesity-associated sleep apnea, cyanosis, somnolence, muscle twitching, and periodic breathing.

Synonyms

Obesity-Hypoventilation Syndrome (OHS); Syndrome de Pickwick (French Appellation).

History

Named after the fat boy Joe, in Charles Dickens’s The Pickwick Papers. This disorder is characterized by morbid obesity, cyanosis, somnolence, muscular twitching, and periodic breathing.

Incidence

The true prevalence in the general population is unknown but estimated to be 0.15 to 0.3% based on population statistics. In the United States, it is observed in 20 to 27% of obese children and adolescents. Higher mortality and morbidity is reported in this group of patients. During the second decade of life, females are more affected than males; 80% of teenagers with obesity will remain affected in adulthood.

Pathophysiology

Reduction in lung volumes including expiratory reserve volume, vital capacity, and functional residual capacity. Closing capacity is increased, leading to airway closure in the dependent areas of the lung and V/Q mismatch, reduced chest and diaphragmatic excursions, decreased alveolar ventilation, and diminished sensitivity of the respiratory center to hypoxia and hypercarbia—all contributing to hypoxia and hypercarbia. Intermittent upper airway obstruction and hypoxia during sleep with resultant chronic sleep deprivation and daytime somnolence; severe and chronic hypoxia leading to polycythemia, pulmonary hypertension, right ventricular hypertrophy, and failure. Leptin and insulin-like growth factor-1 (IGF-1) have been proposed as potential contributors to the blunted ventilatory control. Leptin acts as a respiratory stimulant in the hypothalamus and is increased in morbid obesity patients suggesting a leptin resistance. IGF-1 is also reduced in these patients may affect diaphragmatic muscle strength.

Diagnosis

Clinical features; biochemical (polycythemia, hypoxia, hypercarbia); lung function tests (reduced lung volumes including total lung capacity, functional residual capacity, vital capacity, and expiratory reserve volume); ECG (right axis deviation); chest radiography or echocardiography (cardiomegaly); sleep studies (obstructive sleep apnea).

Clinical aspects

Morbidly obese, lethargy, drowsiness, headache, and muscle twitching; may develop mental retardation; exertional dyspnea, cyanosis, and periodic breathing, particularly marked during sleep, enuresis; hypertension and later signs of chronic cor pulmonale (distended neck veins, enlarged heart and liver, peripheral edema). Major improvement is usual following nasal continuous positive airway pressure at night: daytime sleepiness and behavioral problems regress, and a better quality of sleep allows enhanced physical activity and favors weight loss. Bariatric surgery is beneficial to achieve sustained weight loss. Tracheostomy and ventilation is no longer a realistic treatment option.

Precautions before anesthesia

Detailed preoperative cardiac and respiratory assessment is required; some weight loss might be advisable prior to elective surgery. Noninvasive ventilation should be optimized prior to surgery.

Anesthetic considerations

Difficulty in maintaining patent airway during mask ventilation and difficult tracheal intubations common; arterial desaturation usually ...

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