Sleep Procedures & Testing

(See also

sleep room

Sleep testing can involve various procedures oriented towards diagnosing sleep disorders or treating or following up (monitoring) such disorders.  No test is perfect and physicians must weigh the quality of a test to decide how much stake to put into it and judge its influence on medical decision making and recommendations to the patient.  In the extreme case, the physician may decide that a particular test is deeply flawed and its data must be discarded and decisions based on other sources of information.  Alternatively the physician may decide to repeat the test. Questionnaires are also used to document specific sleep symptoms.

 A polysomnogram is a sleep study conducted in a facility and the patients stay overnight under the supervision of a trained sleep technologist.  Many lines of data are collected and this is probably the most reliable sleep study.

dr. albinoFrom the brain (EEG or electroencephalogram) sensors or electrodes collect information on whether the patient is asleep or awake.  If sleeping, the stage of sleep is determined and whether REM (Rapid Eye Movement) is present, when dreaming usually occurs.  Clearly sleep apnea refers to events during sleep, not wakefulness, and sleep apnea is usually worse during REM.  The EEG can also detect seizures that may be confused with other sleep events such as REM Behavior Disorder that also has a characteristic EEG pattern.  Other illnesses such as Fibromyalgia have a recognizable pattern.  It is best to collect EEG data in a facility, since portable or home testing is often not adequate and overall not cost effective.  A trained sleep technologist must apply the sensors or electrodes and maintain them throughout the night.

Sensors are placed over the nose and mouth to detect airflow or whether the air moves in and out of the nose and/or mouth.  This data is combined with information from belts around the chest and abdomen that indicated air moving in and out of the lungs or effort of breathing. If there is no air flow at the nose/mouth (apnea) but the belts indicate chest and abdominal effort then this is an obstructive apnea, or obstruction in the back of the throat.  If there is no airflow and no belt motion or lack of any breathing effort then this is a central apnea, or the brain did not give an adequate command to breathe.   It is important to distinguish between these 2 apneas since they are treated differently.  Obstructive apneas characteristically involve snoring while central apneas usually do not.

A very important sensor, an oximeter, is placed over a finger to detect oxygen saturation and pulse. Apneas (by definition lack of breathing) can lower oxygen if they last long enough, usually over 10 seconds.  A patient with obstructive sleep apnea will intermittently lower their oxygen saturation during the night especially during REM and while supine (on their back). 

An electrocardiogram (EKG or ECG) is also recorded since apneas can lead to arrhythmias and this is one of the reasons to treat.

Sensors are placed over the legs to detect leg movements that can disturb the patients’ sleep. The wires from these sensors are all placed on a jack box and this in turn is plugged into an amplifier and then the signals are transmitted to a computer.  If a patient has to go to the bathroom it takes only a few seconds to unplug the jack box and place it around the patient’s neck like a large necklace and the patient can go to the bathroom.

sleep roomUsually the patient arrives at the sleep lab in the early evening and leaves in the early morning.  Sensor paste in the hair and body can easily be removed with water.  In our laboratory we do not use oil base glues to hold sensors or electrodes in place.

Some patients worry about not sleeping at the lab, but more than 90% do since sleepiness is one of their main complaints to begin with.  Rarely, a mild short-acting, modern sleeping pill is used to induce sleep that minimally affects the sleep information obtained.

Polysomnograms can be done to diagnose sleep problems, treat them, or follow up and monitor them. Often a diagnostic study is done to document sleep apnea and its severity, then a titration (therapeutic study) is done whereby PAP (either CPAP-continuous positive airway pressure, or “BIPAP”—bilevel positive airway pressure) is used to control the sleep apnea, or both are accomplished in one night using a split night study, i.e. in one night half of the study is diagnostic and the other half is therapeutic.  In a split night study, the right conditions have to be present.  (See Instructions for Polysomnography under the FORMS TAB)

Portable or Home Testing:
Testing at home can be done using oximetry alone or oximetry with airflow (sensors at nose or mouth) and effort (belts around chest and abdomen) information.  Other data can be gathered at home but the information becomes progressively more expensive to obtain, more prone to problems, and more difficult to interpret. Usually EEG (brain) data is not collected so it’s not clear when the patient is asleep or awake or how the data correlates with the sleep state.

In the future, Medicare and other insurances will pay more for home testing but patients must be carefully screened.  The elderly, patients with cardiopulmonary or neurological problems, thin patients, those with little if any snoring,  uncooperative patients, and patients with other potential sleep problems (parasomnias, narcolepsy, periodic leg movements) are not good candidates for home testing to diagnose specific sleep problems.  Portable testing is also problematic in treating sleep problems especially if very low oxygen is involved. 

Portable home testing is more for the young or middle aged obese patient who snores loudly, stops breathing at night, and is inappropriately sleepy during the day.  Thus there is a strong suspicion of “pure” obstructive sleep apnea.  If this patient is otherwise healthy (no cardiopulmonary or neurological disease, no use of alcohol or drugs, and no suspicion of other sleep problems) then Obesity Hypoventilation Syndrome and severe hypoxemia (low oxygen) should be ruled out and the patient is a candidate for portable testing to diagnose sleep apnea.

Treatment is another matter and the physician can make an educated guess as to the PAP (positive airway pressure) settings or an “auto-PAP” can be used.  This is a “smarter” (technologically advanced) but more expensive machine that decides its own settings within a range given by the physician.  Close follow up is necessary.  Also the physician needs to guess as what mask (nasal pillows, nasal mask, or full face mask—covering nose and mouth) should be used.  In the overnight polysomnogram both the settings on the PAP machine and the mask are carefully selected and proven to work.

Medicare will promulgate guidelines in March, 2008 that will probably repeal an old requirement that to prescribe PAP treatment for sleep apnea a polysomnogram (overnight sleep study) is required.  Instead portable or home testing can be used at the discretion of the physician.  Indeed it’s a good idea to give physicians more flexibility by allowing a greater variety of tests in order to diagnose sleep apnea.  Many patients refuse to go to a facility and undergo an overnight study, while others may not have the proper insurance or financial resources. However, given more tests, more expertise in the field of sleep medicine is required, not less.  The physician must know what test to use, under what circumstances, in which patient, and weigh the validity of the results.

An abnormal overnight oximetry (assuming the patient was mostly asleep) by itself only means that the patient’s oxygen saturation dropped during the night.  This could be due to obstructive or central sleep apnea (or a mixture of the two), or to lung disease, heart disease, neurological disease, drugs, obesity itself, infection, or technical problems with the study creating artifacts.  There are certain characteristic desaturation patterns of sleep apnea but these not specific without data also showing airflow obstruction causing these oxygen desaturations.  Clearly the study is not as important as the physician interpreting the study who should have considerable experience and knowledge about sleep medicine.  (See Instructions for Oximetry under the FORMS TAB)


Sleepiness during the day (EDS or excessive daytime sleepiness) is one of the hallmark symptoms of sleep apnea.  It is documented by a Sleepiness Questionnaire and the one most commonly used is called the Epworth Sleepiness Scale, which most patients fill out or the provider does.  It’s very helpful if the patient is quite sleepy but many patients underestimate their sleepiness or are very good at covering it up or confuse it with fatigue.  Often the spouse is a more reliable source of information and can describe the sleepiness better than the patient.  With treatment the sleepiness usually improves though this may take days to months. 

Lack of daytime sleepiness does not rule out sleep apnea, and particularly patients with heart or lung disease or active lifestyles, may deny sleepiness all together.  Often it is only after treatment, and the patients compare the difference, that they finally admit their sleepiness and fatigue before treatment.

It is sometimes very difficult to distinguish sleepiness from fatigue or just being plain tired.  If the patients actually fall asleep when they are relaxed and passive (after lunch in their recliner) then sleepiness is indeed involved but otherwise it can be difficult.

Daytime sleepiness can be caused by many disorders including: sleep apnea, insomnia of any cause, Restless Legs Syndrome/Periodic Leg Movement Disorder, drugs and medications, psychiatric (depression) and psychological (boredom) conditions, sleep deprivation,  neurological conditions (narcolepsy), and circadian rhythm disorders (shift work, sleep phase disorders).   It is the responsibility of the physician to tease out the cause, prove it (diagnosis), manage it, and improve the patient.

Snoring is the second hallmark symptom of obstructive sleep apnea when it arises in the back of the throat.  Snoring can also arise in the nose.  It is usually worsened by alcohol, colds, allergies, sleeping on the back (supine), gaining weight, and aging.  Women snore less loudly than men and admit it less, but are more prone to it during pregnancy and after menopause.  It should be emphasized that snoring is not a major symptom of central sleep apnea.  Using PAP therapy usually completely eliminates the snoring in obstructive sleep apnea, and thus the bed partner is very thankful.  Throat surgery ameliorates the snoring but does not necessarily treat the sleep apnea.  Snoring is difficult to document but in the lab snoring sensors are used.

General medical and sleep questionnaires are also necessary for the patient with suspected sleep disorders.  (See the FORMS TAB). As noted above, there are multiple causes of sleepiness and snoring, while almost any disease and drug can impact sleep and its disorders.

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