Your physician may recommend a sleep study to evaluate your sleep symptoms and establish a diagnosis. These are the common study options.
This is a study done in the sleep lab that is performed with a technician in attendance. The technician will perform a “hook up” that will involve placing anywhere between 12 and 20 wires on the body with either an adhesive material or attachment belts respiratory effort. This study allows us to measure the pattern of sleep stages through the night by monitoring limited EEG (brain wave) channels. Other physiologic parameters include airflow through the nose and mouth, respiratory effort by measuring the chest, as well as oxygen levels by finger oximetry. These Respiratory parameters are monitored to evaluate for obstructive or central sleep apnea. There is also a measurement of muscle activity in the limbs to assess for periodic limb movements. This testing also includes continuous measurement of EKG.
Potentially during this study airway pressure therapy could be introduced by the technician if significant apnea is observed. (in which case we are deriving diagnostic information and in the 2nd half of the study confirming therapeutic response to airway pressure therapy-this is known as a “split night” study)
Home sleep apnea testing (HSAT)
This study is one that is performed at home. The device is a small recorder with several wires and a nasal cannula is designed to identify and quantitate the severity of sleep apnea. It is not able to make any assessment about the quality of sleep as few of these devices also include EEG. There also was usually no muscle channel to assess limb movements.
Nasal CPAP Titration Study
Nasal CPAP Titration Study is a polysomnogram during which the technician, who observes the patient from a control room, has applied a nasal mask to the patient and then remotely and gradually increases the pressure at the nasal interface while the patient is asleep. This allows the sleep specialist to determine the proper amount of pressure required at the nasal interface to alleviate the sleep apnea, irrespective of the body position or stage of sleep the patient may be sleeping in. The nasal interface is carefully chosen to avoid air leaks through the nose or mouth.
Multiple Sleep Latency Testing (MSLT)
Multiple Sleep Latency Testing (MSLT) is a series of naps taken in the sleep lab under observation by a technician. During these naps the patient is monitored by an EEG. This study allows the clinician to assess the severity of the patient’s sleepiness and also to identify whether or not Narcolepsy is present. Parameters monitored during these naps include “sleep latency” (the amount of time it takes the patient to fall asleep during a nap) and an assessment of whether or not rapid eye movement (REM) sleep occurs during this nap.
A Maintenance of Wakefulness Test (MWT)
A Maintenance of Wakefulness Test (MWT) is a study that assesses the patient’s ability to maintain vigilance (wakefulness). This study is usually performed in a patient already on therapy for a known sleep disorder. The goal of this study is to assure that the therapy is effective enough to keep the patient awake to safely carry out normal (and sometimes dangerous) activities such as driving or operating heavy machinery. The application this is usually limited to commercial drivers.
Actigraphy is a tool used in patients that have various forms of insomnia or problems with their biologic clock (circadian disorders). This device looks very similar to a wristwatch and allows a patient’s wake and sleep cycle to be roughly estimated based on activity that is measured during wakefulness versus the lack of activity that is noted during sleep.