Diagnosing Obstructive Sleep Apnea

Obstructive sleep apnea occurs when a person repeatedly stops breathing while asleep when the airway becomes temporarily blocked or narrowed. This condition is a type of sleep-disordered breathing, a group of conditions involving interrupted breathing, often during deep sleep. Sleep specialists at NYU Langone diagnose the condition when breathing stops more than 5 times per hour for longer than 10 seconds each time. Severe obstructive sleep apnea may cause up to 300 pauses in breathing over the course of 1 night.

Obstructive sleep apnea occurs most often during deep sleep, when an airway blockage obstructs breathing. The obstruction resolves when a person experiences a partial awakening, known as arousal. The arousals interfere with the quality of sleep and result in daytime fatigue.  

Many people with sleep apnea are not aware of the airway obstructions or arousals, even if they occur many times a night. Some people wake up more than once during the night without knowing why. And a bed partner may point out another common symptom: loud snoring. Loud snoring is almost universally present in people with sleep apnea.

The symptoms of fatigue brought about by the arousals include memory loss, foggy thinking, and difficulty focusing during the day.

Obstructive sleep apnea rarely goes away on its own. Severe sleep apnea—in which breathing stops at least 30 times per hour—lowers the amount of oxygen in the blood, which places extra stress on the heart and blood vessels. Repeated episodes of apnea increase the risk of high blood pressure and other circulatory illnesses.

The condition occurs more often in men and in people over age 50. Another risk factor is being overweight, which causes the muscles of the throat to relax and block the airway during deep sleep, resulting in sleep apnea. Drinking alcohol or taking sleep aids or sedatives before bed may also increase the risk.  

Causes of Obstructive Sleep Apnea

Obstructive sleep apnea is most often caused by a loss of muscle tone in structures in the upper airway. These include the back of the tongue; the soft palate, a layer of muscle and connective tissue located at the top of the throat; the uvula, a small fleshy lobe that dangles from the back of the soft palate; and the tonsils, small, oval lumps of tissue located on either side of the tongue at the back of the throat.

In most people, these structures are mildly stiff, even during sleep. But in people with obstructive sleep apnea, muscle tone in the upper throat is lost during deep sleep, causing these soft tissues to flop into the airway and obstruct airflow.

Snoring is the mildest result of the loss of muscle tone in the upper airway. As a person breathes in and out, the relaxed uvula and soft palate flutter and vibrate, making noise.

If the structures of the upper throat—including the back of the tongue—lose muscle tone so profoundly that they collapse, they may completely obstruct airflow and prevent a person from breathing. If this occurs for more than 10 seconds at a time, more than 5 times per hour, it is considered obstructive sleep apnea.

A person may be at higher risk for obstructive sleep apnea if he or she has an unusually long soft palate, an unusually large uvula, large tonsils, or an unusually small space between the back of the tongue and the throat. In those who have a smaller-than-average airway, even a mild loss of muscle tone can cause an obstruction.

A less common cause of obstructive sleep apnea is an obstruction of the nasal passages that prevents airflow through the nose. For example, a deviated septum occurs when the strip of cartilage separating the nose into two cavities is pushed to one side, which may obstruct breathing through the nose. Similarly, enlarged turbinates, the bony ridges that line the sides of the nasal passages and help cleanse and humidify air, may block airflow through the nose.

In children, enlarged adenoids, small tissues similar to tonsils located in the back of the nasal cavity, may contribute to airway obstruction during sleep.

Diagnostic Tools

A doctor may recommend one or more diagnostic tests to examine the structures of the nose and throat and analyze breathing patterns while you sleep. He or she uses the results of these tests to determine whether obstructive sleep apnea is causing your symptoms.

Medical History

Details about your past and current health enable doctors to match physical symptoms with their causes. Doctors may ask when you first noticed daytime drowsiness or fogginess and whether these symptoms occur daily or sporadically. Waking up unexpectedly throughout the night with a racing heartbeat or waking up in the morning with a headache may be signs that you have obstructive sleep apnea.

Doctors prefer that you bring your bed partner with you to your appointment, if it’s possible. Your partner may know more about your sleep habits than you do, including how frequently or loudly you snore or gasp for breath.

Fiber-optic Endoscopy

Fiber-optic endoscopy is a diagnostic exam that provides detailed images of the upper airway, including the nasal passages and throat. This allows doctors to evaluate the size and shape of these structures in assessing whether you have an anatomic predisposition to obstructive sleep apnea, such as a small space between the back of the tongue and the throat.

A fiber-optic endoscope is a thin, flexible instrument with a light source at the tip that provides doctors with a clear, magnified image of the upper airway. To perform a fiber-optic endoscopy, doctors spray the nose with a decongestant to open the nasal passages. He or she may also numb the nose and throat with an anesthetic spray. The doctor then inserts the endoscope through the nose and into the airway. This procedure lasts a few minutes and takes place in your doctor’s office.

An endoscopy of the nasal passages and throat can reveal sources of obstruction, including a deviated septum, enlarged turbinates, or narrowing of the space behind the tongue.

Overnight Sleep Study

Doctors rely on the results of an overnight sleep study to confirm the diagnosis of obstructive sleep apnea and identify the causes of airway obstruction. Also called polysomnography, an overnight sleep study reveals the frequency and duration of breathing interruptions during sleep. It also measures the degree of oxygen deprivation that may result.

Experts at NYU Langone conduct hundreds of sleep studies each year in people of all ages. They have streamlined the process to make it a painless and easy experience. During your overnight stay, a sleep technologist attaches small electrodes to your face, head, and chest. They then monitor and record electrical signals related to activity in your brain and muscles.

Monitoring equipment also measures your body position; for example, a sleep study can reveal whether your apnea occurs mostly while you are sleeping on your back. Sleep technologists also measure your heart rate, breathing rate, and the level of oxygen in your blood during the sleep study.

You may think it unlikely that you’ll be able to sleep while attached to this equipment, but most people have no trouble falling asleep.

After a sleep study, doctors analyze a detailed report. Changes in heart rate and breathing rhythms and fluctuation in the amount of oxygen in the blood are among the common indicators of sleep apnea. Doctors also make an audio recording during the sleep study to analyze the pattern and loudness of snoring.

If doctors identify obstructive sleep apnea within the first few hours of the study, they may wake you up and take measurements to fit you for a continued positive airway pressure, or CPAP, mask. This device, which consists of a small air pump connected by a hose to a mask that fits over your nose or mouth, helps open the airway during sleep and is a safe. It is an effective treatment option for any person diagnosed with obstructive sleep apnea.

Typically, it takes three to four weeks to get the full results of a sleep study. Your doctor schedules an appointment to discuss them and the appropriate treatment options.

Occasionally, doctors arrange for a home sleep study that a person can administer without assistance. This test is not as comprehensive as an overnight sleep study at NYU Langone’s sleep lab, but it can confirm the diagnosis of obstructive sleep apnea.

A home sleep study may be recommended in people who are elderly, ill, or unable to travel to the sleep lab. The test consists of a small device attached to the body with straps or wires. These devices record sleep noises such as snoring and monitor your heart rate, breathing patterns, and oxygen levels in the blood.

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