Symptoms & diagnosis of obstructive sleep apnea
An important point is that the patient is frequently unaware of apneic events except for disturbed sleep; he or she also may be unaware of subtle signs of intellectual impairment. An interview with the spouse is quite informative.
Conditions associated with sleep apnea include obesity (in about 60% of cases), anatomic abnormalities (e.g., nasal obstruction, micrognathia, retrognathia, adenoidal or tonsillar hypertrophy, macroglossia), and endocrine disorders (e.g., hypothyroidism and acromegaly).
Use of alcohol and other sedatives may contribute by depressing activity of upper airway muscles. As noted, an increase in the incidence of sleep apnea due to aging (ie, in persons over 60 years old) may not be pathologic.
The clinical features of obstructive sleep apnea are intimately related to the pathogenesis of the disorder. Night time events are characterized by loud snoring (due to airway narrowing), episodes of apnea (due to total airway collapse), and a loud resuscitative snore accompanied by restlessness (due to partial arousal and relief of obstruction).
During waking hours, a perception of unrefreshing sleep, an occasional morning headache, excessive sleepiness, intellectual impairment, and personality changes are noted. Daytime sleepiness is the most frequent complaint and may occur during active situations, such as driving or operating machinery.
In addition to history taking and physical examination, a procedure such as overnight polysomnography is used to aid in the diagnosis of obstructive sleep apnea.
The diagnosis of obstructive sleep apnea is often suspected when the patient's history reveals the salient clinical features just described. A study found that the subjective evaluation based on patient interviews correctly identifies only 52% of patients with obstructive sleep apnea and correctly excludes 70% of patients without sleep apnea. In patients with a low predicted probability of sleep apnea, a model based on characteristic clinical features had high sensitivity, allowing its use as a screening test.
Physical examination should include assessment for maxillofacial abnormalities (micrognathia or retrognathia) and speech dysfunction and careful examination of the upper airway (possibly by an otorhinolaryngologist) for abnormalities of the tongue, epiglottis, larynx, throat, tonsils, adenoids, and nose.
For a polysomnography study, technicians attach three electrodes to the patient's chest to measure heart function during episodes of apnea. The patient also has two so-called strain gauges, one attached with a dissolvable cement to the upper chest, between the nipples, and another across the lower abdomen. These measure the force and frequency of chest and belly expansions as the patient fills his lungs with air.