What Are We Looking at during your Sleep Study

Your doctor has asked you to come to the sleep lab for a sleep study.  You make the appointment, fill out all the paperwork and arrive for your study.  Your technician introduces themselves and gives you a tour of the lab.  You see where the technician sits and you think.  Really what are they looking at?

Here is a small behind the scenes look at what the technician will be seeing during the night.  It will also explain why there are so many wires and why it takes so long to attach them all.

There are three images that the technician will be looking at.  The video of you, the electrical signals the wires are giving off and the signal from a CPAP machine if it is being used.

The video is used for several things.

•  Determining what position you are sleeping.
•  To watch if you need assistance
• To watch for activity such as leg and arm movements, movement during REM and Parasomnias, such as sleepwalking.

The CPAP machine is to assist with your breathing if you have been diagnosed with obstructive sleep apnea.  We watch to see what pressure you are on; if the mask you are using is having issues or the volume of air you are moving.  This helps us to determine if the pressure is working for you or if we need to increase or decrease the pressure.  It also helps us determine if we may have to change the mask you are wearing.

The most complex image watched is the computer screen with the electrical impulses from your body.  Although the screen can be set up differently depending on the type of study and the facility, all the items on the screen are the same.  The first thing the technician will be watching are the wires from your head.  Theses wires tell us when you are awake and when you are asleep.  It will also tell what stage of sleep you are in.  There are 4 stages of sleep that people cycle throughout the night. 

On the face we monitor eye movements and chin movements.  The eyes and chin help us to determine when you reach a stage of sleep known as REM, when you dream.  The chin leads also allow us to know if you grind your teeth in your sleep.  This problem can sometimes cause disruption of sleep.

We use several items to monitor your breathing. 

•  A cannula that monitors the change in pressure when you breathe
•  A thin wire by your nose and mouth that measure changes in temperature when you breathe.  This allows us to determine when you are breathing
•  Two belts, one around your chest and one around your belly, which measure the movements of breathing.  The reason for the two belts is because your breathing can happen more in the belly than chest or vice versa.  It also tells us when you are having trouble breathing because the chest and belly will move opposite of each other.
•  We also have a microphone to measure snoring which may be on your neck or it may be on your forehead.

You can see that we are very careful about how we monitor your breathing because we need to not only know when you are breathing but if you are having issues what type of problem it could be.

We also monitor you heart and your oxygen levels.  We use a clip on your finger that measures the oxygen by shining a red light through your finger.  The amount of light the sensor reads is based on the amount of oxygen attached to your red blood cells.  The heart rate it measure by two electrodes placed on the chest.

The final signal comes from the electrodes placed on the legs.  Some people have muscle movements during the night, the leg leads will monitor for those movements.

As you can see the technician is quite busy during the night evaluation the signals and video they are viewing throughout the night.  Their job is to make sure the signals are as clear as possible for the physician to read and to understand what is going on during the night so they can be of assistance to you, their patient, when needed.

I hope you will feel a little more comfortable when you visit the lab for your study.

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