Diagnosis of Obstructive Sleep Apnea Syndrome

Diagnostic Evaluation of Obstructive Sleep Apnea Syndrome

The diagnostic "workup" for patients with suspected obstructive sleep apnea syndrome (OSAS) focuses on the following areas:

• Patient history
• Physical examination
• Polysomnography

Patient History

The patient history represents the first opportunity to carefully interview the patient about signs and symptoms that would prompt the health care provider to suspect the possibility of obstructive sleep apnea syndrome. Patients who suffer from OSAS often present to a doctor with a chief complaint of excessive daytime sleepiness and fatigue. They may also complain of frequent arousals at night, morning headaches, impaired concentration/memory, nocturia, mood swings, and a decreased interest in sexual activity. It is prudent for the patient to also bring their bed partner to the initial visit with the doctor because they can often attest to witnessing other symptoms (e.g., sleep apnea, habitual snoring) about which the patient may or may not be aware.

Physical Examination

If the patient history is consistent with signs and symptoms of obstructive sleep apnea syndrome, the doctor will perform a physical examination during which he/she will look for physical conditions that may be associated with OSAS, including:

• Is the patient overweight or obese?
• Is the patient's blood pressure elevated?
• Does the patient have any nasal problems (e.g., nasal congestion; deviated septum; nasal polyps)?
• Are there any anatomical abnormalities that may contribute to airway collapse (e.g., large tongue; elongated uvula; enlarged tonsils)?
• Does the patient have a normal or an enalarged neck circumferenece?
• Does the patient have pulmonary hypertension?

Abnormal findings on physical examination are not diagnostic for OSAS per se but must be followed-up with additional tests to rule out other conditions and establish an accurate diagnosis.

There are currently no specific blood tests available for the diagnosis of OSAS. Your doctor, however, may order selective blood tests in order to rule out other conditions. Your doctor may also wish to determine if you have low levels of oxygen in your bloodstream while you are sleeping (a condition called hypoxia). This can be measured by a device called a pulse oximeter that is attached to your finger while you are asleep. Although pulse oximetry is useful for screening patients for OSAS, establishing a definite diagnosis can only be accomplished by polysomnography (sleep test).

Polysomnography

Polysomnography (overnight sleep test) is considered to be the most accurate test available for establishing the diagnosis of obstructive sleep apnea syndrome (OSAS). Polysomnography is usually performed in a hospital or a "sleep center" where specialized equipment is available to monitor a variety of physiological parameters while the patient is asleep. Polysomnography is a painless test during which a series of wires and probes (electrodes) are attached to various parts of the body to monitor and record the following body functions during sleep:

• Brain wave activity
• Leg muscle tension
• Eye movement
• Oxygen levels in the bloodstream
• Heart rate and rhythm
• Airflow measurements during breathing and exhaling
• Audio monitoring to record sounds made during sleep (e.g., snoring; gasping for air)
• Movement of the chest and abdominal muscles during respiration

During polysomnography, episodes of apnea (cessation of breathing lasting for 10 seconds or longer) and hypopnea (decreased rate and depth of breathing lasting 10 seconds or longer) are recorded. The number of apnea/hypopnea episodes per hour of sleep is calculated and is expressed as the apnea-hypopnea index (AHI). The AHI is the basis for determining whether or not a patient has OSAS. The AHI scores for patients with OSAS can range from a minimum of 5 to a maximum of 30 or higher. In general, patients with severe OSAS have higher AHI scores than those with mild or moderate OSAS. Most experts agree that an AHI score of 5 or higher in patients with excessive daytime sleepiness is sufficient to establish the diagnosis of OSAS. For a variety of reasons, it is not always possible to make a diagnosis of OSAS with a single polysomnography and, for some patients, the sleep test may have to be repeated on a second night.