What Is Adaptive Servo-Ventilation (ASV)?
ASV is a specialised therapy mainly used for central sleep apnea. Here's how it works, who it's typically prescribed for, and an important safety point for people with certain heart conditions.
In this guide
What is ASV?
Adaptive Servo-Ventilation (ASV) is a type of non-invasive ventilation used primarily to treat central sleep apnea (CSA), as well as mixed/complex sleep apnea and Cheyne-Stokes respiration. Unlike standard CPAP, which delivers a steady or auto-adjusting pressure aimed at obstructive apneas, ASV continuously monitors the patient's breathing pattern and adjusts support breath-by-breath to smooth out irregular breathing patterns typical of central sleep apnea.
How ASV works
ASV devices rely on algorithms that track the patient's own breathing pattern in real time and adjust pressure support accordingly — increasing support during periods of reduced breathing effort, and backing off when the patient is breathing adequately on their own. In effect, the device "fills in" only when needed, rather than delivering a fixed or simply auto-ranging pressure.
ASV devices use the same masks and tubing as standard CPAP and BiPAP units — no specialised accessories are required.
The benefits of ASV
Compared to standard CPAP or BiPAP, ASV's main advantage is its ability to respond dynamically to central apnea events and unstable breathing patterns — particularly Cheyne-Stokes respiration — that fixed-pressure or purely auto-adjusting therapies aren't designed to address. For appropriately selected patients with central or complex sleep apnea, this can mean more stable breathing overnight and better tolerated therapy than BiLevel therapy alone.
Important: ASV and heart failure
ASV is contraindicated for a specific group of heart failure patients
Following the 2015 SERVE-HF clinical trial, ASV therapy is contraindicated for patients with symptomatic chronic heart failure with reduced ejection fraction (LVEF ≤45%) and predominant central sleep apnea. The trial found an increased risk of cardiovascular mortality in this specific patient group when treated with ASV, leading manufacturers including ResMed to update their labelling and safety guidance accordingly.
This is a formal contraindication, not simply a "less suitable" option — patients in this category should not be started on ASV therapy, and those already on it should have this reviewed with their cardiologist and sleep specialist.
This is exactly why ASV — more than most PAP therapies — must only be prescribed after proper diagnostic testing, including an assessment of cardiac function where relevant.
Other conditions where ASV isn't recommended
Beyond the heart failure contraindication above, ASV therapy is generally not recommended for patients with:
- Chronic hypoventilation
- Moderate to severe chronic COPD
- Restrictive thoracic disease
- Neuromuscular disease
- Chronically elevated arterial CO₂ (PCO₂)
This list isn't exhaustive. Whether ASV is appropriate always depends on a full diagnostic workup by your doctor or sleep specialist, not on this general summary.
ASV vs. CPAP vs. BiPAP
CPAP, BiPAP and ASV are the three main forms of positive airway pressure therapy, typically prescribed in that order of escalation when earlier therapies aren't effective enough.
CPAP
A single, continuous pressure. Usually the first-line therapy for obstructive sleep apnea.
BiPAP
Two separate pressures — one for inhalation, one for exhalation. Often considered next if CPAP alone isn't sufficient.
ASV
Pressure support that adapts breath-by-breath, mainly for central or complex sleep apnea rather than as a general step-up from CPAP.
Your doctor decides between these based on your diagnostic testing — this isn't a therapy you or your equipment provider should choose without a formal sleep study and prescription.
ASV devices
ResMed AirCurve 10 ASV with Heated Humidifier
A widely used ASV device with an integrated heated humidifier for comfortable overnight therapy.
See the AirCurve 10 ASV →Frequently asked questions
Is ASV safe for everyone with central sleep apnea?
No — ASV is contraindicated for patients with symptomatic chronic heart failure with reduced ejection fraction (LVEF ≤45%) and predominant central sleep apnea, following findings from the SERVE-HF trial. Suitability always needs to be confirmed by your doctor, including a cardiac assessment where relevant.
What's the difference between ASV and BiPAP?
BiPAP delivers two fixed pressures — one for inhaling, one for exhaling. ASV goes further, continuously adjusting support breath-by-breath in response to your actual breathing pattern, which is particularly useful for central and complex sleep apnea.
Can I switch from CPAP or BiPAP to ASV myself?
No — the choice between CPAP, BiPAP and ASV should always be made by your doctor based on proper diagnostic testing, not decided independently.
Does ASV use special masks?
No — ASV devices use the same masks and tubing as standard CPAP and BiPAP machines.
Please note: this guide is for general information and isn't medical advice. ASV carries a specific contraindication for certain heart failure patients — whether it's appropriate for you must be determined by your doctor or sleep specialist based on proper diagnosis, including cardiac evaluation where relevant.
