What Do All Those Wires Do?

At the start of your sleep study, you will be hooked up to the recording equipment with a comically large amount of wires and tubes.  You’ll probably feel like you are in that pod in the movie The Matrix. But what do all these wires do? What are you really being hooked up to, and how does it contribute to your polysomnogram?

Though the order in which these machines are connected may change, here is an outline of what wires are placed where and why, going from the least amount of connections to the most:

• A Pulse Oximeter is a small clip that will most likely be attached to your index finger, though it is also commonly attached to an ear lobe. It measures the levels of oxygen in your blood throughout the test, in order to determine whether or not your sleep disorder is limiting your blood oxygen (a dangerous effect of obstructive sleep apnea.)
• Two connections will be made near your eyes, with one placed slightly above the outside corner of your right eye and the second placed slightly below the outside corner of your left eye. These two electrodes provide information for an electrooculogram, or EOG, which measures the movements of your eyes. Recording your eye movements is essential for your sleep study, as it will determine not only when you fall asleep, but whether or not you are in REM sleep.
• You will also be connected to an electrocardiogram, or EKG, to measure your heart rate throughout the test. Generally, an EKG for a sleep test only uses two electrodes, however more may be used if you are in need of a more detailed report. They are usually placed slightly beneath the collarbone and slightly above the waist. It is important to measure your heart rhythms in order to rule out any underlying heart problems you may have that are interfering with your sleep.
• An electromyogram, or EMG, measures the contractions of your muscles and will add an additional four electrodes, one below your bottom lip and one under your chin, as well as two more near your shin. Measuring muscle contraction is important, as it is also an indicator of the onset of sleep, and REM sleep. This metric can also diagnose sleep disorders relating to muscle movements during sleep.
• The most wires you are likely to experience can be blamed on the electroencephalogram, or EEG. Typically, this test will require 8 electrodes to be placed on various portions of your head. The EEG will track detailed information of your brain activity throughout the night, in order to help doctors decide what stages of sleep you go through and when.
• Typically, you may also be subject to a small hose that clips beneath your nostrils to determine if, and how hard you are breathing. Sometimes, there may also be a camera or microphone in the room to track your movements visually or measure the severity of your snoring.

Except for the EEG, these electrodes are generally fastened to you with peel and stick pads. Due to the fact that most people appreciate their hair, the EEG electrodes are connected with a sticky and conductive putty, and don’t require any hair removal.

All things considered, while it may seem imposing and uncomfortable with the amount of hookups required, a sleep study is a very important step in determining your sleeping disorder.