Why do we need sleep studies?
Sleep disorders occur while the patient is sleeping. The patient is rarely aware of the problem, unless it creates a problem during the waking hours, such as excessive daytime sleepiness or chronic respiratory problems. Though we can ask many questions, or examine a patient in the office, ultimately we need to examine the patient while he/she is having the problem, namely during sleep. The most common diagnosis we study in the sleep lab is sleep apnea. Other illnesses include narcolepsy, sleep movement disorders, sleep deprivation syndromes, and fibromyalgia.
What is involved in a sleep study?
The patient spends a night, or in some cases a day, sleeping in the sleep laboratory. Electrodes and sensors are attached to the skin to measure many parameters in order to monitor: brain waves, muscle activity, and eye movement in order to score sleep stages; respiratory movement, oxygen level, airflow; heart rate and rhythm.
What is a Multiple Sleep Latency Test?
Some patients need to perform a test of how long it takes to fall asleep to evaluate excessive sleepiness. This test takes about a day. The patient is offered 5 opportunities to fall asleep. The time to enter various stages is recorded. Between each session the patient must stay awake for one hour. This test has significance in patients with narcolepsy.
What is CPAP?
In many cases of sleep apnea, a mask is applied to the face, connected to a compressor that generates a flow of air. This device is called continuous positive airway pressure, or CPAP. The flow of air through the nose splints the airway open in the back of the throat. This prevents the obstruction in the throat that causes sleep apnea. The pressure and flow need to be adjusted to an optimal level while the patient is sleeping. Too much is as bad as too little. When the right pressure setting is achieved, the patient should have virtually no apnea episodes. Another version, called bilevel positive airway pressure, nicknamed BiPAP, allows more flexible adjustment independently of inspiratory and expiratory pressures.
What is done with the data?
After the study is completed the data is analyzed by computer and reviewed by the sleep technician and the sleep physician. The entire night of sleep is scored in 30 second blocks for sleep staging, and respiratory events. Based on the data, therapy is prescribed or recommended. Sometimes the study has to be repeated to perform a trial of CPAP if it was unable to be done on the first night. Often the worst apnea events occur too late in the night to allow enough time to do a good CPAP trial.
How can a person really sleep in a strange place with all of those wires and headgear?
It certainly seems like it should be difficult, yet most patients with sleep apnea do fall asleep quite readily. The lab is kept quiet and is furnished quite comfortably to simulate a home environment. A TV is available as well as reading material, and a refrigerator. One is not confined to the bed. A person may get up and walk around or go to the bathroom.
How does a patient know if the sleep study was a good study?
The most important thing is whether or not the patient slept. Once asleep, the patient should demonstrate a complete spectrum of sleep stages. All channels of data must be clear and provide accurate data. One reason why home studies that are unattended are not desirable is that if a wire becomes disconnected, an entire night of data is lost. If there is apnea, it should be able to be demonstrated on multiple occasions. Sometimes the apnea may be subtle and is only truly apparent after the study is scored and reviewed in detail at multiple scanning speeds or adjustments of settings.
Is the CPAP trial necessary if surgery or a dental appliance is planned already?
Depending on the type of surgery or dental apparatus, it is still often useful to observe the response to CPAP to prove reversibility of the condition. Also while waiting for surgery or waiting for a dental appliance to be made, CPAP can be started and used temporarily. Many types of surgeries are done, the most simple being nasal septoplasty or tonsillectomy, as well as uvulopalatopharyngoplasty. More aggressive surgical intervention depends on the severity of the apnea, or the anatomic abnormalities observed by the ear, nose, and throat physician. The Klearway is one of the more popular, and well tolerated dental appliances to advance the mandible (jaw) and make the back of the throat (pharynx) larger, thus relieving obstruction to airflow. The dentist makes a mold of the teeth and fits the patient for the mandibular advancement appliance.
What happens after the study?
If CPAP needs to be started, it will be ordered within 24-72 hours. The patient receives a preliminary report, pending the final scoring of the study. The patient will need to make an appointment to meet with the sleep physician within a few weeks to review the results as well as the response to CPAP. If other therapeutic options are necessary, they can be discussed further at that time.
