THE PATIENT with a hypoventilation syndrome 1 generally complains of easy fatigability, hypersomnolence, and morning headaches and exhibits irritability and mental deterioration. Dyspnea is rarely prominent unless lung disease is present. On examination, tremor, twitching, cyanosis, and irregular respiration may be observed. The irregularity in respiration is particularly apparent during sleep. There may be evidence of right ventricular hypertrophy which can be confirmed by roentgenograms of the chest and/or the electrocardiogram. Polycythemia without leukocytosis or thrombocytosis and an elevated serum bicarbonate are common. The essential finding is an elevated arterial carbon dioxide tension (paCO2). Although hypoxemia is usually present, normal arterial oxygen tensions may be recorded if the patient has hyperventilated immediately prior to the study. With such an increase in ventilation, hypoxemia is reversed quickly, but the carbon dioxide retention is corrected more slowly.
The etiology of this syndrome is varied (Fig 1). Most frequently it is the