A patent nasal airway is essential for good sleep since the oral airway is unstable and tends to obstruct during sleep. Not surprisingly diseases of the lower airways and other parts of the respiratory system, when they significantly impair lung function, also disrupt sleep. Symptoms of sleep disturbance are more common in patients with COPD than in the general population. The symptoms are similar to other insomniac conditions, i.e., prolonged sleep onset latency, increased awakenings, reduced sleep efficiency, and fatigue on awakening, except that the patient can usually relate them to cough and episodes of dyspnea. Patients frequently report daytime sleepiness.
Sleep studies confirm sleep disruption and document the characteristic oxygen desaturation.
Although oxygen therapy can correct the sleep-related hypoxemia, sleep disturbance to some degree usually persists. This indicates that factors other than hypoxemia contribute to the syndrome. Sleep disruption is also a common feature of asthma. Recent investigations relate nocturnal asthma to increased bronchial inflammation and to greater bronchial hyperreactivity. Dosing of corticosteroids and theophylline to increase the drug effect during the night can significantly improve lung function and nighttime sleep.