Obstructive Sleep Apnea (OSA) is characterized by recurrent, functional collapse during sleep of the velopharyngeal and/or oropharyngeal airway, causing substantially reduced or complete cessation of airflow despite ongoing breathing efforts. This leads to intermittent disturbances in gas exchange (eg, hypercapnia and hypoxemia) and fragmented sleep.
While upper airway collapse can occur during both rapid eye movement (REM) sleep and non-REM sleep, decreased genioglossus muscle tone during REM sleep significantly increases the propensity for upper airway obstruction. As a result, the severity of OSA in REM sleep is striking in some individuals. There is some evidence that REM-predominant sleep apnea may exacerbate the adverse cardiovascular and metabolic effects associated with OSA.
The severity of OSA in any given individual is influenced by other factors as well, including upper airway anatomy, arousal threshold, upper airway muscle drive, and stability of the respiratory control system. In addition, the underlying pathophysiology may vary by age, with younger patients more likely to have alterations in ventilatory control and older patients more likely to have predominant upper airway collapsibility.
Snoring and daytime sleepiness are common presenting complaints of OSA. While both symptoms are relatively sensitive, they lack specificity for the diagnosis. In a systematic review of the accuracy of the clinical examination in the diagnosis of OSA, the most useful individual finding for identifying patients with OSA was nocturnal choking or gasping, which was associated with a sensitivity and specificity of 52 and 84 percent.
Additional symptoms and signs may include restless sleep, periods of silence terminated by loud snoring, fatigue, poor concentration, nocturnal angina, nocturia, and morning headaches. Common findings on physical examination include obesity, a crowded oropharyngeal airway, large neck circumference, and hypertension.
A variety of clinical prediction rules and scores have been evaluated using easily obtained and interpreted signs and symptoms of OSA. However, their sensitivity is generally much higher than their specificity such that when the score is low, the likelihood of OSA is low.
In-laboratory polysomnography is the first-line diagnostic study when OSA is suspected. However, home sleep apnea testing (HSAT) may be an acceptable alternative for patients who are strongly suspected of having OSA and who do not have medical comorbidities (eg, heart failure) that require more detailed or additional sleep-related measures (sleep stage, arousals, leg and arm movements, seizure monitoring, etc).
The diagnosis of OSA is made based upon a combination of an increased frequency of obstructive apnea events during sleep and daytime signs or symptoms of disturbed sleep. In adults, a diagnosis of OSA is defined by either of the following: