How to Interpret Sleep Study Results
Interpreting sleep study results is not something that you can do easily, or correctly, without your doctor. In fact, many physicians are unclear about the significance of all of the data on a sleep study technical report.
The first step to understanding sleep study results is to put the test into context. Why was the study ordered?
Most of the time, the sleep test was ordered in order to rule out or diagnose sleep apnea. However, sleep studies can be used to assess for other sleep disorders.
It is important to realize that a sleep study technical report contains very much data. Some reports are 5-pages long and contain dozens, if not hundreds, of numbers.
The sleep study technical report will contain information about the stages of sleep, breathing episodes, heart rate, oxygen levels, snoring, muscle movements and other parameters.
The ‘Sleep Efficiency‘ quantifies the amount of minutes of total sleep time divided by the total recording time. The higher the sleep efficiency, the higher the percentage of sleep vs. wake. Many reports will tally the amount of wake time, Stage 1,2,3,4 and REM sleep.
Of course, sleeping with electrode wires on your head, a finger probe, and chest belts, is going to interfere with your typical night’s sleep. However, most sleep test data is adequate to rule in or rule out a sleep disorder.
The ‘Apnea Hypopnea Index‘, or AHI, is the amount of apnea and hypopneas that occur per hour of sleep. An apnea is a total obstruction of breathing for over 10 seconds. A hypopnea is a partial obstruction. Generally, in adults, over 5 events per hour is considered an abnormal AHI, and is suggestive of sleep apnea. The number is different in children.
The ‘Oxygen Desaturation Index‘, or ODI, is the number of times that the oxygen level drops during sleep. This is often used as a surrogate or supporting variable in assessing for sleep disordered breathing.
Generally, oxygen levels are expected to hover above 90%.
The heart rate is often measured. Generally, the hear hovers between 60 – 100 beats per minute during sleep. Over 100 BPM is call tachycardia. Under 60 BPM is call bradycardia.
You primary care provider or sleep physician should review the sleep study results with you after you have completed your sleep study. Once the results have been discussed, you will come up with a treatment plan that is based on your medical history, your results, and your preferences.
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