How to Diagnose Sleep Apnea

Most doctors know how to diagnose sleep apnea, although classifying it as a specific type is sometimes difficult.  Here’s a look at the tests used in the diagnosis process and what they reveal to your doctor.

Polysomnography

A polysomnography or PSG is more commonly referred to as a “sleep study”.  This is an overnight test typically performed in a special clinic, although it can be performed in a hospital.
The PSG is used in the diagnosis of other conditions as well, including narcolepsy, seizure disorders, parasomnias, periodic limb movement and REM disorders.  When the main complaint is daytime fatigue, doctors order a PSG to find out which (if any) condition is interfering with the person’s ability to get the rest they need.

During the polysomnogram, a number of different devices are attached to the patient.  Since the equipment and the attachments can cause anxiousness and/or interfere with a patient’s ability to fall asleep, he or she is usually instructed to arrive at the clinic several hours before bedtime. 

By the time bedtime arrives, the patient is usually comfortable with the equipment and the technician.  The technician will remain in the room or nearby in order to monitor the equipment and observe the patient’s sleeping behavior.

Although some doctors may feel that evaluating a patient’s reported symptoms is how to diagnose sleep apnea, there is a general agreement that the PSG is more accurate.  It can also reveal underlying health problems in the cardiovascular or nervous system.

The devices attached to the patient measure brain activity, eye movements, blood oxygen levels, chest and upper abdominal movements, heart rate and rhythm, leg movements and nasal airflow.  Snoring may also be recorded or simply noted by the technician as mild, moderate or loud. 

Loud snoring is recognized as one of the symptoms.  The technician may also be able to see that the patient stops breathing or struggles to take a breath at various times during the night. 

How to Diagnose Sleep Apnea with Portable Monitoring Devices

Polysomnography may be undesirable for a couple of reasons.  The costs may be prohibitive.  That’s the usual objection.

Some patients simply cannot fall asleep in the laboratory environment.  Even after being introduced to the equipment, they are unable to relax.

Researchers have learned how to diagnose sleep apnea through the use of portable monitoring devices.  Although they are still not widely used, the devices are a good alternative to PSG.

The simplified tests are used at home.  The patient is taught how to set up the devices and attach the monitors prior to sleep.  Only a couple of the measurements taken during a PSG are measured by the portable devices.  Typically, the patient’s heart rate, breathing, airflow and blood oxygen levels are measured.

Because the device cannot detect all types of apneas, a PSG may still be necessary.  For example, the central type is usually detected by changes in brain activity.  Still, the portable devices are a less expensive option.

CPAP Titration Study

Not only is PSG considered how to diagnose sleep apnea correctly, it may also be used to determine whether or not treatment is effective and for other purposes.  During the additional sleep studies, it is not usually necessary to attach all of the different monitoring devices, although blood oxygen levels and heart rate are usually monitored. 

The standard treatment for the obstructive type is CPAP; continuous positive airway pressure.  A CPAP titration study may be ordered to determine the correct amount of pressure to use to keep the airways open and prevent apnea episodes.

CPAP titration studies are performed in the same laboratory environment as the standard PSG study.  A clinician is present to choose the right mask size and type.  Some masks cover the nose and mouth.  Some cover only the nose.

Split Night Studies

In some cases, the PSG test for diagnosing sleep apnea is combined with the CPAP titration study.  The combined tests are referred to as split night studies.  Here’s how that works.
There are certain standards for how to diagnose sleep apnea that is clinically significant; treatment is necessary.  These standards are measured during the PSG. 

When one or more is detected, the diagnosis can be confirmed by the technician monitoring the results.  The results that indicate clinical significant apneas are:

• 10 seconds or more between breaths
• Changes in EEG frequency indicative of the central type
• Blood oxygen levels 3-4% lower than normal
• Six or more apnea episodes during any single hour of sleep

When a technician notes these results during the first half (four hours) of the night, the technician may wake the patient and begin the CPAP titration study.  The style of mask is chosen and fitted.  The correct pressure is determined. 

If severe apneas are noticed quickly, the technician may decide to wake the patient and begin treatment before four hours have passed.  It is often possible to make a diagnosis quickly, once the patient falls asleep.

After the split-night study has been completed, the patient does not usually have to return for further follow-up studies.  He or she goes home armed with the CPAP machine and hopefully will begin to rest better at night.

The benefits of the split-night studies include lower cost and less disruption to the patient’s life.  What might normally take two or three nights can be accomplished in one.

Other Tests that May be Useful

What you have learned about so far is usually how to diagnose sleep apnea and other sleep-related disorders.  But in some cases, the overnight studies are inconclusive. 

If one of the patient-reported symptoms is excessive daytime sleepiness or fatigue, a multiple sleep latency test (MSLT) may be useful.  The test measures how long it takes a person to fall asleep during daytime naps.  The theory is that the less time it takes for the patient to fall asleep, the sleepier they actually are. 

The test is considered objective and can also be used to determine whether or not treatments are working.  If a comparative MSLT is done prior to treatment and another is performed afterwards, there should be a noticeable improvement.  

To learn more about how to diagnose sleep apnea, talk to your doctor.  If you have symptoms, you can get an accurate diagnosis and an effective treatment to help you get your rest.