While you are sleeping, important brain and body functions are measured and recorded. This may reveal that you have a breathing problem during sleep. A common example of this kind of problem is obstructive sleep apnea. In this case, the technologist may awaken you. He or she will fit you with a mask. It will either cover your nose or your nose and mouth. Another version has soft silicone tubes that fit directly in your nostrils. These are called nasal pillows. The mask provides you with a steady stream of air that gently blows into the back of your throat. This treatment is called positive airway pressure (PAP). While there are three kinds of PAP, the most common uses a level of pressure that remains continuous (CPAP).
You will try sleeping for the rest of the night with the mask. The technician will find the right level of air pressure to help you breathe normally as you sleep. This process is called a CPAP study. Usually your doctor will know in advance if there is a chance that this may occur. He or she will discuss this with you ahead of time. The use and purpose of the device will be explained to you in detail. You may even get to try on a mask and test it before your sleep study begins.