AHI PARAMETERS

[codger]

A major goal of CPAP/APAP therapy is to get AHI (Apnea/Hypopnea Index) below 5. My average AHI is around 6.

My sleep doc advised me that an AHI below 10 is considered a successful therapy. My machine manufacturer in its literature also states that an AHI below 10 is successful treatment.

My machine manufacturer defines an apnea as a 10% or less open airway for 10 seconds, and a hypopnea as an airway open 50% or less for 10 seconds.

Do all machine manufacturers define apneas and hypopneas in this way? I notice that my machine, in its clinician's menu, will let you set a different AHI definition, i.e. a 30% airway closure, rather than 50%, for a hypopnea event.

Is my machine delivering the same AHI readings as other machines, and if not, would my AHI readings be higher with other machines, assuming that my machine defines hypopnea at a 50% or greater closure for 10 seconds?

[PaulaO2]

Yes, the guidelines say the goal is an AHI of 5 or less. As far as I know, nearly all machines rate them the same, as in an event is not logged unless it lasts for 10 seconds or more.

As for the hypopnea limit, not sure on that one. Wikipedia says:

In the context of diagnosis and treatment of sleep disorders, a hypopnea event is not considered to be clinically significant unless there is a 30% (or greater) reduction in flow lasting for 10 seconds or longer and an associated 4% (or greater) desaturation in the person's O2 levels, or if it results in arousal or fragmentation of sleep.

If you want accurate AHI according to the "gold standard", then put it at this.

I think it's odd that it is even changeable!

[zonk]

according to American Academy of Sleep Medicine (AASM) there are two definitions for scoring hypopnea
1- hypopnea requires at least a 30% reduction in airflow for at least 10 seconds
2- hypopnea requires at least a 50% reduction in airflow for at least 10 seconds
http://www.ncbi.nlm.nih.gov/pubmed/19238801
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R.13. What is meant by "BASELINE" in the new AASM scoring manual? We are using the alternative definition for hypopnea in non‐Medicare patients. Hypopnea is defined as > 50% drop in the nasal pressure signal compared to baseline associated with either a 3% desaturation or an arousal. I am meeting with our techs on a regular basis in an attempt to insure uniform scoring under the new criteria. I have attached a typical example. The labeled events are those scored by the technologist. There are other events present which are associated with arousals which the tech did not score because he did not believe that there was a 50% drop in flow. There is a 50% drop in flow compared to the recovery breaths but this may not be "baseline" in that the patient is hyperventilating in response to the event. Is it acceptable to use the amplitude of these three to four breaths following the event as "baseline" and compare the reduced breaths to these?

If there is no clear baseline breathing to measure, due to a high frequency of abnormal respiratory events, then the recovery breaths between the frequent apneas or hypopneas would be acceptable to use for an approximate baseline against which to measure the percent of drop for the next reduction in airflow.


http://www.apneaboard.com/forums/Thread-...-Questions

[codger]

The ResMed S9 Autoset uses this definition for a hypopnea:[/i][/b]

Hypopnea
A hypopnea is an episode of shallow breathing during sleep. A hypopnea is scored when there is a reduction in breathing by 50% of baseline breathing with partial upper airway obstruction for 10 seconds or more. The event is scored after 10 seconds of the hypopnea.

So at least my machine is reporting hypopneas in a standard way. Good to know.