What is ASV? Treating Complex and Central Sleep Apnea
What is ASV (Adaptive Servo Ventilation)?
Adaptive Servo Ventilation (ASV) is a non-invasive ventilatory treatment option created specifically for the treatment of adults who have obstructive sleep apnea and central and/or complex sleep apnea. It's one of the newer positive airway pressure (PAP) units on the market that continuously monitor the patient's breathing problem.
Want to learn how split night studies work to detect central apneas a patient? The AAST offers a CEC-eligible course module on Split Night with Central Apnea here.
In a way ASV is similar to (CPAP) therapy that is used in the treatment of obstructive sleep apnea but there are significant differences. (Not sure how CPAP works, excatly? Refresh your memory here.)
ASV's pressure target is adjusted according to the input from the patient. What that means is that the target is not a fixed value but rather adapts to the patient's breathing patterns. Because the device continuously adjusts itself to meet the patient's needs, the discomfort often reported by PAP patients is avoided altogether since the machine's pressure changes are subtle in a way that makes the patient feel comfortable.
How ASV machines work
Whenever the ASV machine detects abnormalities in breathing, it intervenes with just enough support to maintain the patient's breathing at 90% of what had been normal for that patient prior to the abrupt change in breathing. When the patient's breathing problem ends, the machine adjusts itself to this normalcy.
When the patient's breathing is stable, ASV provides just enough pressure support to provide an approximate 50% reduction in the work of breathing for the patient, therefore making the machine use much more comfortable for the patient.
How is ASV different from other PAP treatment options?
Until ASV entered the market as a treatment option, sleep technologists worked with three positive airway pressure (PAP) machines.
1. CPAP (Continuous Positive Airway Pressure), which delivers the same pre-set pressure continuously.
2. BPAP (Bilevel Positive Airway Pressure), which senses when the patient is beginning to exhale and responds by dropping the delivered pressure transiently to make exhalation easier.
3. BPAP with intermittent mandatory ventilation (IMV), which also senses when the patient stops breathing and responds with a delivery of breaths at a pre-set pressure and a pre-set rate.
The most common complaints associated with PAP therapy are related to the discomfort caused by the fact that it is usually the patient that has to get used to the machine and not the other way around.
But ASV devices are unique in that they are "smart." They continuously adapt to the patient's breathing patterns and are considered to be more comfortable for the right patient than the three PAP options listed above.
ASV is for the following types of patients:
- Patients with complex sleep apnea (central apneas emerging with use of CPAP or bilevel PAP therapy).
ASV is NOT for the following types of patients:
- Those who have chronic and profound hypoventilation.
- Those who have moderate to severe chronic obstructive lung disease.
- Those who have chronically elevated partial pressure of carbon dioxide on ABG (arterial blood gas) (> 45 mm Hg).
- Those who have restrictive thoracic or neuromuscular disease.
A word of caution when prescribing ASV to patients
On May 13th, 2015, ResMed issued a press release and related Urgent Field Safety Notice, “An update on Phase IV SERVE-HF Study of Adaptive Servo-Ventilation (ASV) Therapy in Central Sleep Apnea and Chronic Heart Failure.” ResMed and regulatory authorities cautioned against the use of ASV therapy in patients with symptomatic chronic heart failure (NYHA 2-4) and reduced LVEF</=45%, AND moderate to severe predominant central sleep apnea.
On May 15th, Respironics responded to the update. Respironics is conducting their own investigation and working with ResMed in order to better understand the ResMed study data. Until more information is available both companies are recommending that physicians should assess individual risks before prescribing ASV therapy for the at-risk patient population. No other patient populations have been identified as at-risk for adverse outcomes.
The AASM released a statement on May 15th as well. The AASM recommends that:
- Physicians stop prescribing ASV to treat central sleep apnea in patients with symptomatic heart failure and LVEF ≤ 45%,
- Before starting a patient on ASV, each patient should be assessed for the presence of heart failure, and if heart failure symptoms are present, an objective assessment of LVEF be performed to see if they are in the higher risk group, and
- Prior patients with symptomatic heart failure and with an ejection fraction ≤ 45% whom you have treated with ASV since 2005 should be contacted to advise them of the risks and strongly consider recommending that they stop ASV treatment. Which alternative treatments for central sleep apnea to recommend, if any, will need to be individualized.
What is the role of the sleep technologist in this situation?
- Be sure your medical director is aware of the results of the SERVE-HF study and discuss the information in the links below.
- Develop a plan with your medical director for responding to this urgent announcement. The role of the sleep technologist may include:
- Helping to identify patients currently treated with ASV (one method would be to review ASV titrations)
- Contacting patients and providing information as authorized by your medical director.
- Review your policy and procedures manual and consider with your medical director whether modifications to achieve compliance with current treatment recommendations are necessary. Any patient authorized for ASV titration should be evaluated for heart failure.
- Monitor the AAST and AASM web sites for additional information.
The AAST also has great resources on ASV, Check out the following online modules: