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 monitors and adjust to correct the patient's breathing problem.
In one way, ASV is similar to CPAP therapy that is used in the treatment of obstructive sleep apnea, but there are significant differences.
ASV's pressure target is adjusted according to 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.
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 re-adjusts itself to the patient's normal breathing pattern.
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 therapy 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 a lower pressure 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 the patient usually 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 pattern 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
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.
[Update]: "SERVE-HF did not meet its primary endpoint, however this study provides valuable, practice-changing guidance on how to best care for people with chronic heart failure," said Prof. Martin Cowie, M.D., the co-principal investigator of the study and Professor of Cardiology at Imperial College, London."
Note: ASV is consistently in use in appropriate patients, with most sleep physicians continuing to avoid this therapy for patients with heart failure and LVEF