Sleep-Disordered Breathing

Clinical Presentation. Pronounced snoring, a classic indicator for possible sleep apnea is related to vibration of upper airway tissue. Apnea occurs when the upper airway obstruction becomes complete. There is decreased blood oxygen saturation with corresponding increased blood carbon dioxide levels leading to arousal from sleep. The patient is usually unaware of these events; however, the bed partner is aroused and understandably frightened by the patient’s respiratory pause. Paradoxically, the majority of patients with obstructive sleep apnea do not report choking or gasping for breath and are unaware of their apneas. Although they may feel that the have slept well, they exhibit excessive daytime sleepiness, which results in lapses in attention and inappropriately falling asleep. Impairment of cognitive function may mimic depression or dementia, and children with sleep-disordered breathing show problems with attention and behavioral dyscontrol that may disrupt their schoolwork. Severe cases (≥30 episodes per hour) and possibly those with moderate degrees of apnea (15 to 29 episodes per hour) are at significantly increased risk for cardiovascular disorders, including hypertension, myocardial infarction, cardiac arrhythmias, and stroke. Hypertension may develop from elevated catecholamine levels caused by the apneas. In addition, the negative intrathoracic pressure caused by struggling to breathe may lead to increased secretion of aldosterone, promoting increased intravascular fluid volume. The elevated central venous pressure paired with increased intrathoracic negative pressure increases transmural forces affecting the heart, which may cause cardiovascular remodeling and alteration of cardiopulmonary physiology. Sleep loss also causes insulin resistance, which can predispose to diabetes and increased body mass, which further worsens the sleep apnea and hypertension.

Diagnosis and Treatment. An all-night sleep study is the best means to detect and quantify apneic events. Healthy adults may experience up to four apneas per hour of sleep at night; in children more than 1.5 events/hour is considered abnormal. Treatment of obstructive sleep apnea begins with correction of anatomical abnormalities of the airway, including removal of enlarged adenoids and tonsils in children. Reduction of risk factors, such as obesity and drinking alcohol in the evening, may help. If this is not curative, continuous positive airway pressure (CPAP), which uses air pressure to splint open the airway during sleep, prevents apneas and reduces daytime sleepiness and cardiovascular risk. Patients with severe and moderate sleep apnea significantly benefit from CPAP use by improving daytime alertness and reducing cardiovascular risk. Often, the treated patient may comment that he had not realized how sleepy he was until he had experienced the results of treatment.

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