Scoring Obstructive Hypopnea vs. Central Hypopnea
Sleep technologists are very familiar with obstructive apneas, central apneas, and mixed apneas. Many technologists also believe they know how to identify hypopneas and break those hypopneas apart into what Medicare recognizes as the definition of/criteria for a hypopnea and what other entities recognize as the definition of/criteria for a hypopnea.
However, lately the big questions seem to revolve around what is an obstructive hypopnea versus a central hypopnea, and why do I need to know the difference?
Lucikly, the AAST has a wide-range of resources to help sleep technologists differentiate between the two. Read on to learn more, or watch our video on defining central sleep hypopneas here .
What was old is new again
Central hypopneas have been known for a long time. My copy of The Altlas of Sleep Medicine by John W. Shepard from 1991 has an example of a central hypopnea within it. We knew they were part of the cyclic pattern of Cheyne-Stokes breathing.
The medical field has been aware for a long time that there is an association between the Cheyne-Stokes breathing pattern and congestive heart failure.
The fact that patients with neuromuscular disorders or hypoventilation syndromes involving failed respiratory drive had central hypopneas was also long known. The problem was what to do about them.
Originally the only means we had to treat any sleep related breathing disorder was with Continuous Positive Airway Pressure, or CPAP. However, the patient response was poor if they were suffering from any respiratory disorder that was central in nature.
When Bi-level ST modalities came around we saw improvement in treating central sleep disordered breathing, but still there was a poor response for many patients that had more complicated issues.
Somewhere along the line, the distinction between obstructive hypopneas and central hypopneas simply got lost and labs began to score and report hypopneas as one entity. That is now changing.
Treating the patient with the appropriate therapy
Our goal as sleep professionals is to treat patients and stabilize their breathing patterns. To do this we need to use the correct equipment for the job.
Whereas obstructive apneas and even obstructive hypopnea events respond well to CPAP, most central events respond better to other treatment modalities.
Central apnea events are usually well controlled with either the pressure support provided with Bi-level or even the additional support of a back-up rate provided with Bi-level ST.
However, central hypopneas are not well controlled on any of these three devices. To control the more complex patient with central hypopneas you are going to need the more advanced therapy provided by Adaptive Servo Ventilation (ASV).
If you are not recognizing the difference between obstructive and central hypopneas, you are going to have a hard time utilizing the correct device for the job.
There's those dreaded words "coverage" and "cost"
Because of the complicated nature of ASV machines, they are expensive. It is difficult for patients to pay for them, even if they have insurance.
Most insurers want to make sure you have eliminated the less expensive devices ability to control the patient's sleep disordered breathing and show a true need for these advanced therapy devices.
Patients with complex breathing patterns may not have central apneas, but only central hypopneas as part of that waxing and waning breathing pattern. Without enough central events documented, insurance coverage can become difficult to obtain.
Scoring and reporting separately on obstructive and central hypopneas, rather than grouping them together, gives you the documentation you need to show that this is the device your patient needs.
So how do I tell obstructive and central hypopneas apart?
It is an Obstructive Hypopnea if ANY of the following are present:
Snoring during the event
An increase in the flatting of the nasal pressure flow or PAP flow signal
You can only call the event a Central Hypopnea if NONE of the above is present.
That's it! With a bit of practice and observation, you can identify the difference between the two and find the correct device modality and pressure for your patient.
Zzz you later,
Want to learn more about central hypopneas? Watch "Are We Ready to Define Central Hypopneas" by Dr. Conrad Iber, MD, in which he discusses a method for automated recognition of central hypopneas that covers the pathophysiology of central events, scoring rules, and treatment options.