5 things you need to know: Central Apnea & ASV therapy

If you've never heard of central sleep apnea and don't know what ASV is, don't worry.

Neither are common, but a lot of discussion has centered on both central sleep apnea and ASV in the last year because of safety concerns.

Check out our primer on these specialty sleep health topics.  

 

First things first: A review

Because central sleep apnea is less common, it's always a good idea to review what it is and why ASV is still considered one of the best approaches available for treating it.

Central sleep apnea basics

Unlike the more common obstructive sleep apnea (OSA), central sleep apnea syndrome (CSAS) refers to sleep apnea that is the result of neurological dysfunction (as opposed to mechanical obstruction). 

Essentially, central apneas occur when your brain fails to deliver signals to your diaphragm to breathe automatically as you sleep, or the signals are delivered in an erratic fashion that affects your ability to get adequate oxygen as you sleep.  

 

Twenty percent of all cases of sleep apnea are categorized as CSAS, but 30 percent of chronic heart failure (CHF) patients develop CSAS. 

CSAS is also caused by side effects from using certain medications like opioids.  

Adaptive Servo-Ventilation (ASV) basics

ASV is a form of noninvasive ventilation. Like continuous positive airway pressure (CPAP) therapy, it includes a bedside machine, tubing, and a mask.

However, unlike CPAP, it's programming is far more complex. ASV is said to be "smart": it detects the user's breathing patterns on a breath-per-minute basis, even when patterns are erratic, and intervenes in order to maintain breathing that is at 90 percent or better of what your normal patterns might resemble. 

5 things you need to know: Central Apnea & ASV therapy

1.  The best applications for ASV therapy

These days, "smart" medical devices are all the rage, and for good reason: they can be customized for specific applications in a way that offers tremendous relief for people who suffer from complicated medical conditions like CSAS.

The following situations are well suited for an application of ASV therapy: 

Abnormal breathing patterns are a feature of sleep breathing disorders of central origin

Cheynes-Stokes Respiration (CSR) is an abnormal sleep breathing pattern with neurological origins. Its waxing and waning wave patterns crescendo into stretches of deep (and sometimes fast) breathing, to be followed by decrescendos into very shallow respirations; eventually, this pattern causes apnea.

2. Understanding the limitations of ASV in certain CHF patients 

Just over a year ago, results were announced for a major study (the Serve-HF study), which examined the impact of ASV on health outcomes for people suffering from chronic heart failure. Researchers issued a caution: their findings showed ASV was no longer a safe choice for a very specific subset of CHF patients. 

In patients with CHF, sleep breathing instability shifts between extremes—hyperventilation, in which rapid breathing results in too much oxygen in the blood, and hypoventilation, in which shallow, slower breathing leads to unacceptably low levels of blood oxygen. 

A subset of CHF patients who struggled with ASV were identified as those with a heart failure condition known as left ventricular ejection fraction (LVEF). Those with reduced LVEF of less than or equal to 45 percent were shown to have a 33 percent higher risk for cardiovascular death than CHF patients with similar CSAS symptoms who were not using ASV.

More recently, ongoing French research (the FACE Multicentre National Cohort Study) presented additional findings on the use of ASV at a convening of the American Thoracic Society. They revealed that, while subjects with CSAS showed similar levels of heart disease severity, those with predominant CSAS plus higher CHF severity had more unplanned hospitalizations and a higher mortality rate regardless of ASV usage.

The study's lead author, Dr. Renaud Tamisier of Grenoble Alpes University, acknowledged that most CHF patients with CSAS are expected to have a poor diagnosis. However, he asked, "is this related to CHF status?... Patients with the most severe CHF do not seem to benefit from treating their [CSAS] with ASV.”

Until these questions are conclusively addressed, all potential candidates for ASV are now screened by cardiologists to ensure they are qualified to safely use this therapy.

3. Improving exercise capacity with ASV

A July 2016 article in the Journal of Nuclear Cardiology showed statistically significant and encouraging improvements to exercise capacity for ASV users.

Exercise capacity is a measurement of how well you can sustain physical activity. For people with sleep apnea (OSA or CSAS), exercise capacity has been shown to be greatly diminished by either condition.

However, by using noninvasive ventilation (PAP therapies for OSA and ASV for CSAS), you can increase your ability to endure physical exertion, which is important for addressing concerns about cardiovascular function. 

4. Traveling with ASV

The bad news first: there are no portable ASV machines on the market (yet), so patients who want to travel with it will need to take their standard-sized equipment.

However, these devices have been downsized for home use, so your machine may still be easy to pack. Because the FAA considers it a medical device, you don't have to forgo your usual carry-ons, just take it onboard with you. 

Backup power can come by way of backup battery power systems which are also now available for ASV, which makes it possible to go camping or "off the grid" with your therapy.

5. Trialing ASV

In order to start using ASV, you have to qualify for its use. ASV is an expensive therapy tailored to some very specific kinds of medical needs. If your particular sleep breathing disorder can be fixed by a less complicated device like CPAP or BiPAP, then it's not likely you will be granted ASV as an option.

However, if you have shown you qualify for this therapy and have failed all other therapies, your doctor may decide to pursue this option.

Trialing ASV requires that a patient attend a sleep lab overnight to use it under supervision. The sleep technologist will record the patient's baseline breathing patterns for both minimum and maximum pressure support settings, and an appropriate oxygen support setting will also be determined.

This data, which is different from that which may have been collected at previous PAP titrations, is crucial to programming the ASV device for the patient to use effectively at home.

If you have other questions about sleep apnea and potential therapies, don't forget that your sleep specialist is always available to answer them. Please reach out to us at Sound Sleep Health if you have concerns about sleeping problems, for yourself or for a loved one. We have 3 locations in the greater Seattle/Kirkland areas. Call us so we can work together to Improve Your Sleep Today (425) 296-6194.


Sources:

European Respiratory and Pulmonary Diseases
Journal of Nuclear Cardiology
Sleep Review

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