A polysomnogram, also called a sleep study, is a test that records your brain waves, heart rate, breathing and eye and leg movements while you’re sleeping. Sensors placed on your head, face, chest and legs send electrical signals to a computer.
This recording of brain waves and eye movements allows a sleep technologist to determine how deeply you’re sleeping and whether you experience a type of sleep called rapid eye movement (REM).
Breathing monitors capable of detecting changes in air flow and oxygen levels help diagnose the severity of sleep apnea you may have. A finger clip tracks changes in the level of oxygen in your blood. Our sleep laboratory also has the capability of monitoring your ventilation by measuring exhaled and transcutaneous carbon dioxide levels.
Leg sensors show both minor twitches and major movements that can occur during the night.
Polysomnograms take place overnight in the outpatient sleep laboratory. You will be in your own private room with a bathroom, shower and TV.
Polysomnograms are painless. To begin, a sleep technologist applies sensors to your skin and connects them to a computer (the sensors’ wires are long enough to let you move normally in bed). To calibrate the sensors at the beginning of the study, you’ll be asked to move your eyes, clench your teeth and move your legs. The wires are all connected to one main cable; if you need to use the bathroom, the sleep technologist will simply disconnect the main cable and reconnect it when you return.
You are free to read or watch TV. At some point during the night, the sleep technologist will ask you to turn off the lights and TV and try to fall asleep. During your monitoring from a near-by room using a low-light camera, the technologist may return to your room to reapply a loose sensor or if you request assistance.
If you’re worried you won’t sleep during your sleep study, you should know that nearly everyone eventually does. You may not sleep as well as you do at home, but this will not impact your study evaluation. Patients do not need to sleep a full eight hours for an accurate diagnosis. In fact, one to two hours of recorded sleep may be enough to diagnose sleep apnea.
A polysomnogram is recommended in the following cases:
• To diagnose obstructive sleep apnea or other forms of sleep breathing disorders, such as central sleep apnea or sleep hypoventilation.
• To look for behaviors or movements during sleep that can be harmful to the patient or others.
Split Night Polysomnogram with CPAP or Non-invasive Ventilation Titration
If you have significant sleep apnea early on in your sleep study, the second half of the night may be used to determine the continuous positive airway pressure (CPAP) needed for treating your sleep apnea.
At the beginning of the night, you will try on a variety of masks to determine the best fit and comfort. Then, if a split night polysomnogram is needed, the appropriate mask is ready.
Air pressure is first introduced through a CPAP machine at a very low level and then increased during the night. The goal is to find the right level of air pressure that will prevent the collapse of your upper airway. This will eliminate pauses in your breathing and snoring.
A split night polysomnogram with CPAP or non-invasive ventilation titration is recommended in the following cases:
• When significant sleep apnea is detected during the first part of the sleep study.
• To determine the correct levels of positive airway pressure to treat the sleep apnea.
• Non-invasive ventilation can be used in appropriate cases to improve hypoventilation.