While there are many sleep disorders that come under the scope of sleep medicine, the vast majority of the energy of sleep labs and sleep physicians is directed to the diagnosis and management of sleep-related breathing disorders.

 

Sleep-related breathing disorders are diagnosed in the sleep lab (or sometimes by sleep monitors worn in the privacy of the home) by monitoring the breathing process throughout the night. To understand this monitoring process it is necessary to understand a few terms. Apnea is defined as a period of time when breathing stops and the blood oxygen levels drop at least 4%. A hypopnea is a period of time when breathing is severely restricted but not stopped and the blood oxygen levels drop at least 4%. A respiratory effort related arousal (RERA) is a period of time where breathing is difficult enough that the accumulated effort of trying to breathe disrupts or fragments sleep.  Since apneas and hypopneas involve lowering oxygen levels, these events are regarded as more serious than RERAs.

 

Taken together the above terms, apnea, hypopnea and respiratory effort related arousals are referred to as respiratory events.  An apnea/hypopnea index or AHI reflects how many times an hour averaged over a night’s sleep someone has an apnea or hypopnea.  A respiratory distress index or RDI is how many times an hour someone has one of the above respiratory events, an apnea, a hypopnea or a respiratory effort related arousal.

 

With this terminology behind us it is easy to understand what degree of sleep-related breathing disorder someone has: mild, moderate or severe.

 

 

 

 

Someone is considered to have mild sleep apnea if they average between 5 and 14 respiratory events and hour.  Moderate sleep apnea is between 15 and 29 and severe sleep apnea is above 30 events an hour.  What is not often recognized is that the bottom number of 5 respiratory events an hour necessary to get a diagnosis is an arbitrary number.  There are a large number of people with numbers lower than this who suffer greatly from sleep-related breathing disorders who get tested and get no help because they “don’t fit the profile”.  As a rule, oral appliance therapy works wonderfully for these people.

 

The American Academy of Sleep Medicine’s practice parameters state that oral appliance therapy can be used with those patients with mild and moderate sleep apnea as a first line therapy.  This means that, if the patient choses, oral appliance therapy can be used instead of CPAP.  The parameters also state that those patients with severe sleep apnea should use CPAP if at all possible. 

 

TAKE HOME POINT:

•  Many times people have a sleep test and are determined not to need treatment because their respiratory distress index wasn’t high enough to qualify for a diagnosis.   Remember that the bottom RDI of 5 is arbitrary!  A great number of people who snore loudly  get a sleep test and are told they do not have obstructive sleep apnea and do not require treatment.  Yet when these people are treated with oral appliance therapy to eliminate snoring, they experience a much deeper and more restful sleep along with reduced daytime sleepiness and fatigue.