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Sleep Medicine: Understanding a Sleep Study

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Sleep study (polysomnogram) charts your brain waves, heart beat and breathing as you sleep. It also records your eye and leg movements as well as muscle tension. Sensors are placed on your head, face, chest and legs. They send tiny electrical signals to a computer.

The signals show when you are asleep and awake during the night. The brain-wave and eye-movement help us determine the stages of sleep. The breathing monitors show the number of times you stop breathing. They can also detect low air flow and minor changes in oxygen level. The leg sensors show both minor twitches and major movements that occur during the night. A clip will also be placed on your finger to note changes in the level of oxygen in your blood.

A polysomnogram is often used in the following cases:

  • To look for sleep-related breathing disorders, such as sleep apnea
  • To set the correct levels of continuous positive airway pressure (CPAP) in patients with sleep related breathing disorders
  • To go along with a daytime nap study to see if someone has severe excessive daytime sleepiness
  • To look for behaviors during sleep that can be violent or could be harmful to the patient or others

Preparing for the Test

You will be asked to come to the center in the evening. Some time will be given for you to make yourself at home in the bedroom. No other patients will be in the room with you. Should you feel you would need it, you will have to ask your ordering physician for a sleep aide as the technicians cannot provide them.

You will not feel any pain during the polysomnogram. The sensors are gently placed on your skin and connected to a computer. The wires are long enough to let you move around and turn over in bed. You will be asked to move your eyes, clench your teeth and move your legs. This will make sure that the sensors are working.

During the Test

You are free to read or watch TV until your normal bedtime. Then the lights are turned out and it is time for you to try to fall asleep. A low-light video camera allows a technologist to see you from a nearby room. He or she will have to enter your room if a sensor comes loose. He or she will also have to detach the wires if you need to go to the bathroom during the night.

The polysomnogram is not a test that you can fail. Nearly everyone falls asleep during the study. Most people do not sleep as well as they do at home. This will not affect the results. In most cases, you do not need to sleep for a full eight hours to find the source of your problem.

After the Test

In the morning you will test the sensors again, and then they will be removed. This will complete the study, and you will be free to go. You may be tired if you did not sleep well during the night. Otherwise, you can return to normal activities on the day after a sleep study.

Getting the Results

It usually takes about one week to 10 days to get the results of a sleep study. At times the doctor who takes a look at the study needs to get more information. He or she may talk to the technologist or to the doctor who sent you to the center.

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