Sleep Apnea, Snoring, Narcolepsy,
Insomnia and Other Sleep Disorders.



Understanding the symptoms of sleep disorders.




Central Sleep Apnea: Treatment With Adaptive Servo-Ventilation (ASV).

What is adaptive servo-ventilation (ASV)?

-ASV is an exciting breakthrough created by the ResMed Company specifically for the treatment of central as well as obstructive apneas.

How does ASV work?

-ASV is a new form of positive airway pressure unit that continuously monitors the patient's breathing pattern in exquisite detail.

-Whenever it detects significant reductions or pauses in breathing, it intervenes with just enough support to maintain the patient's breathing at 90% of what had been normal for that individual just prior to the decrease in breathing.

-Then, when the patient's breathing problem ends, the machine "backs out" gently.

-Also, when the patient's breathing is stable, ASV provides just enough pressure support to help maintain airway patency: thereby providing an approximate 50% reduction in the work of breathing.

The machine is subtle in its interventions...and it continuously adjusts itself to meet the patient's needs in a manner that will feel normal for that patient at that point in time: which renders it comfortable.

ASV is the ultimate "smart machine".

How does ASV differ from the positive airway pressure machines that we already had available?

-Until the development of ASV, we had only three basic types of positive airway pressure (PAP) machines:

  • CPAP (Continuous Positive Airway Pressure): a simple "blower" that delivers the same pre-set pressure continuously.
  • Bilevel PAP: a machine that senses when the patient is beginning to exhale and responds by dropping the delivered pressure transiently to render exhalation easier.
  • Bilevel PAP with intermittent mandatory ventilation (IMV): a bilevel unit that also senses when the patient stopped breathing--then responding by delivery of bursts of air at pre-set pressures and a pre-set rate to try to stimulate breathing. Its greatest disadvantage was that it would force the patient to try to adapt to the machine rather than the machine adapting to the patient's rate and depth of breathing. Many patients complain that they are unable to synchronize their breathing with these machines. Also, the abruptness with which these units deliver IMV can trigger arousals which in turn can precipitate more central apneas.

-ASV is unique in that it continuously adapts to the patient. It provides just enough support when the patient needs a manner so similar to the patient's own recent breathing pattern and rate that it is not only comfortable, but also, it is unlikely to provoke arousals and more central apneas.

Which patients with central sleep apneas are most likely to benefit from ASV?

-Patients with complex sleep apnea (central apneas emerging with use of CPAP or bilevel PAP).

-Patients with heart failure or atrial fibrillation who have central sleep apnea - with or without obstructive sleep apneas.

How much more effective is ASV in these patients, when compared to the alternatives?

-A study compared the effectiveness of ASV, CPAP, bilevel PAP with IMV and oxygen in patients with heart failure. Here are the results:

Apneas and hypopneas per hour of sleep
per hour of sleep
% of sleep time spent
in REM sleep
% of sleep time spent
in deep, slow wave sleep

*Teschler H et. al. Adaptive Pressure Support Servo-Ventilation. A Novel Treatment for Cheyne-Stokes Respiration in Heart Failure. Am J Resp & Crit Care Med 16: 614-619, 2001

-Only ASV reduced the number of episodes of apnea and hypopnea to normal, and ASV clearly was superior at reducing sleep fragmentation and increasing vital stages of sleep needed for proper rest. All patients preferred ASV to CPAP.

Since ASV adjusts to the patient, are titration sleep center overnight recordings needed before treatment with ASV is prescribed?

-Yes, for two important reasons:

  • There are three parameters of ASV that must be adjusted to the individual patient's needs: the end-expiratory pressure and both the minimal and maximal pressure support settings. As with positive airway pressure in general, these devices must be set just right for the patient or the end result will be much like buying the wrong size shoes. We believe strongly in precise titrations, since problems with positive airway pressure treatment are similar to a piece of gravel on one's shoes: the size of the piece of gravel doesn't matter. If everything is not just right, the patient will be likely to abandon treatment.
  • Insurance companies typically require proof that a treatment is effective before they will pay for it.

-Therefore, if you or a loved one suffers from indications of central sleep apneas--whether from use of CPAP/bilevel PAP for obstructive sleep apnea or as a complication of heart disease, it is important when you select a sleep center for care that you first ensure that the center has ASV machines on site for use during overnight monitoring and that the center's technologists have been properly trained in use of these devices.

Do many sleep centers offer ASV titrations to their patients at this point in time?

-No, for two reasons. First, ASV became available in the United States only recently, and Medicare coverage for this treatment was just granted in April 2006. The latter is very important because most insurance companies now follow Medicare rules when determining what tests and treatments for which they will grant coverage.

-A second problem is that for unclear reasons, a large number of established sleep centers do not attempt to treat central apneas at all: they still do not even offer trials of bilevel PAP with IMV for central apneas despite the fact that the latter have been available in the US since 1990. These centers simply focus on obstructive apneas and routinely prescribe only CPAP or straight bilevel (without IMV) machines. It is difficult to understand why they ignore central apneas, since they complicate positive airway treatment of obstructive apneas in 15-20% of cases and can cause severe sleep fragmentation to the point that patients simply abandon treatement.

-As of late September, 2006, the Columbus Community Health Regional Sleep Disorders Center is the only sleep center in central Ohio with ASV units on site.

What has been the experience with use of ASV at the Columbus Community Health Regional Sleep Disorders Center?

-Overwhelmingly positive. We obtained our first ResMed VPAP Adapt SV in late July, 2006 and have found this treatment so invaluable that we added a second machine in September. As of mid-September, we have already used the device in thirteen patients and prescribed it for home use in twelve patients (the thirteenth slept more soundly during a second overnight study and could be treated with straight CPAP.

-ASV has worked perfectly in all of these patients, normalizing breathing and oxygen levels in all of them while improving sleep quality. It eliminated the need for supplemental oxygen in every case. Several of these patients previously had been struggling to use bilevel PAP with IMV, plus supplemental oxygen, plus sleeping in a sitting position and were doing poorly. They now are sleeping soundly.

-Our ASV experience was summarized in a recent press release, reproduced here:


Revolutionary New Treatment Helps Heart Failure And Sleep Apnea Patients

Columbus Residents Benefiting After Years Of Deteriorating Health And Quality Of Life

COLUMBUS, Ohio - September 5 - One out of every two patients with heart failure repeatedly fails to breathe during sleep. This problem (central sleep apnea, or "CSA") can cause dangerous drops in blood oxygen levels that accelerate deterioration of cardiac function while rendering treatment for heart failure ineffective. This frequently undetected breathing disorder also afflicts many patients with atrial fibrillation.  Until recently, effective treatment for central sleep apnea was unavailable.  Now, a new treatment approach called adaptive servo-ventilation is available at The Columbus Community Health Regional Sleep Disorders Center.

"ResMed's adaptive servo-ventilation device will save the lives of countless individuals who suffer from unstable breathing during sleep," stated Dr. Robert Clark, Medical Director of The Columbus Community Health Regional Sleep Disorders Center.  "I regard it as the greatest single breakthrough in sleep medicine since the development of positive airway pressure itself in the mid-1980s."

A similar condition causes patients with obstructive sleep apnea (OSA) to abandon treatment.  Evan, a 54 year-old slender Columbus man with a history of snoring and daytime sleepiness, demonstrated 95 episodes per hour of obstruction of his throat during sleep, with repeated drops in blood oxygen levels: placing him at dangerously elevated risk of heart attack, heart failure, stroke and accelerated coronary disease.  Then, when placed on positive airway pressure--the leading therapy for obstructive sleep apnea--he immediately developed central sleep apneas.  He repeatedly failed to make any effort to breathe--with even greater decreases in blood oxygen saturations that made his already tenuous condition much worse.

He continued to do poorly despite more aggressive treatments, such as use of home oxygen in conjunction with a variant of positive airway pressure that acts much like a demand ventilator.  Furthermore, he could not tolerate sleeping throughout the night with them.

Evan was then treated with a new technology specifically developed for the management of central sleep apneas--adaptive servo-ventilation (ASV).  The results were dramatic.  When using ASV, he demonstrated entirely normal breathing and oxygen levels throughout sleep, without any need for supplemental oxygen or additional treatments. 

"I am so grateful to Dr. Clark for identifying an appropriate therapy for my sleep apnea.  My health and quality of life were deteriorating rapidly," said Evan.  "Treatment with ResMed's VPAP Adapt SV has improved my daytime alertness and energy levels significantly.  And my wife is delighted both by how much better I feel and by the fact that this new machine is so quiet. At last, we both sleep well!  I believe that other patients who are experiencing frustration over their current sleep therapy regimen can benefit from Dr. Clark's unique experience in this area."

Evan's sleep specialist, Dr. Robert Clark, shares his excitement over this new treatment approach.  "It is a remarkably intelligent and subtle device," says Dr. Clark.  "ASV continuously analyzes a patient's breathing pattern on an ongoing basis and immediately senses when breathing is becoming unstable.  Then, it provides just enough support to ensure stable breathing…and it "backs out" when it no longer is needed.  It is far more comfortable than our prior treatments because it adjusts to the patient's changing needs--rather than forcing the patient to try to adapt to it.  And studies have clearly shown that ASV is far more effective than any other treatment for central sleep apneas in heart failure victims."

Dr. Clark's facility, the Columbus Community Health Regional Sleep Disorders Center, is the only area center to offer adaptive servo-ventilation to its patients.  Twelve of its patients whose sleep apnea had previously been extremely difficult to treat have already been tried on ASV.  It normalized breathing in all twelve and in every case, it eliminated any need for supplemental oxygen.  Oxygen is a costly treatment that renders travel difficult--and oxygen therapy often worsens sleep quality by increasing nasal drying and due to the noise and heat generated by many oxygen concentrators.

"Central sleep apnea can be a devastating problem.  Unfortunately, it can be very difficult to detect, since it often is unassociated with either snoring or sleepiness. Also, the pauses in breathing are not always witnessed by bed partners," Dr. Clark cautions. 

"A high index of suspicion is extremely important," he continues.  "CSA should be suspected in all patients with either significant heart failure and atrial fibrillation, as well as in patients with obstructive sleep apnea who have difficulty tolerating CPAP or bi-level positive airway pressure for unclear reasons.  A timely diagnosis is particularly crucial in severe cases, now that we have such a remarkably effective and well-tolerated solution to offer afflicted patients."

Dr. Clark, who is dually board certified in sleep medicine and neurology, has been actively involved in the diagnosis and treatment of sleep related illnesses since 1975 and has given presentations on sleep disorders in Europe, Canada and South America.  The Columbus Community Health Regional Sleep Disorders Center, fully accredited by the American Academy of Sleep Medicine, sees patients from throughout the United States and other countries.

For more information or to schedule an interview, contact Dr. Clark at the following:

The Columbus Community Health Regional Sleep Disorders Center, 1430 South High Street, Columbus OH 43207; telephone: (614) 443-7800, fax: (614) 443-6960, e-mail:, web site:


Accredited by the American Academy of Sleep Medicine.

Robert W. Clark, M.D., Medical Director
1430 South High Street, Columbus OH 43207

Tel: [614] 443-7800
Fax: [614] 443-6960


  Copyright 20010 Robert W. Clark M.D. Inc.