If you are suspected of having a sleep disorder, your medical provider may recommend that you undergo overnight oximetry, a commonly used screening test. Overnight oximetry is a simple test and it provides basic information that may be useful in initially evaluating whether you have one of the more common sleep disorders, sleep apnea.
This screening test is easy and inexpensive, but it is not perfect. It only provides a limited amount of information. In addition, there are subtleties involved in sleep disorders that it may not be able to detect. Nevertheless it may be useful in identifying some people who warrant further testing, such as sleep studies.
Please stick to your normal routines on the day of the test.
Continue as usual with your medication.
The test involves applying a plastic clip over the end of your finger. Imagine a large clothespin enclosing your fingertip. This clip may be held in place with a piece of tape, but it is not painful to have on and it can be removed easily. It is connected via a cable to a small box that records the data overnight.
Within the overnight oximeter clip is a red light. This red light shines through your finger. On the other side is a sensor that can measure your heart rate and the oxygen content of your blood. The latter is determined by the color of your blood, which will vary with the amount of oxygen. These data are recorded continuously over the course of the night and will result in a graph.
Your consultant will be able to review it and determine if there are abnormal drops in your oxygen levels called desaturations. There may also be associated increases in your heart rate. These events may suggest the presence of sleep apnea because it involves periodic pauses in your breathing and drops in the oxygen level of your blood.