Diagnostic criteria for obstructive sleep apnea
By September 26, 2010 at 12:18 pm 9,601 8 4
How is apnea diagnosed? What are the doctors looking for? What is the difference between mild, moderate and severe sleep apnea?
All good questions. Hope the following information is helpful!
Sleep apnea is diagnosed using an overnight sleep study called polysomnogram.
During the study a lot of data is collected including respiratory air flow, blood oxygen saturation levels, heart rate, muscle activity of legs and chin, sleeping positions, eye movement and the electrical activity of the brain.
The severity of sleep apnea is determined using the AHI or Apnea/Hypopnea Index, also referred to as the RDI or Respiratory Distress Index. This is the total number of apneas plus the total number of hypopneas, divided by the length of the sleep period. An easy way to think about this is how many times per hour do we stop breathing during sleep!
An apnea is the complete cessation of breathing for 10 seconds or more, and sometimes can even last over a minute.
A hypopnea is an episode of reduced airflow (usually by one-third or more) often accompanied by a drop in oxygen saturation and/or a measured arousal in the brain.
AHI or RDI is usually expressed as a number per hour. While standards vary, an index of 10-20 is considered Mild, 21-40 Moderate, and anything greater than 40 is considered Severe Apnea. Anything over 5 is considered abnormal.
Symptoms vary but include snoring or gasping noises preceeded by silence ( the cessation of breath) disturbed or restless sleep, unrefreshing sleep, daytime sleepiness, or other daytime symptoms such as memory loss, inability to concentrate, low libido, headaches.