Adaptive Servo-Ventilation (ASV)
ASV is an advanced, non-invasive ventilation therapy. Unlike standard CPAP which treats obstructions, ASV is designed to treat central apnoeas—where the brain fails to signal the respiratory muscles.
How ASV Works
An ASV machine continuously monitors the patient's breathing volume and rate, establishing a moving baseline target (usually about 90% of the patient's recent average minute ventilation).
When the machine detects a drop in respiratory effort (a central apnoea or hypopnea), it rapidly increases pressure support on inhalation to force air into the lungs, effectively breathing for the patient. Once spontaneous breathing resumes, the machine smoothly drops back down to a minimal support level.
Primary Indications
- Central Sleep Apnoea (CSA): Idiopathic or narcotic-induced.
- Complex Sleep Apnoea (Treatment-Emergent Central Sleep Apnoea): A condition where applying CPAP to treat obstructive apnoeas inadvertently causes the patient to develop central apnoeas.
- Cheyne-Stokes Respiration (CSR): A specific waxing and waning breathing pattern often associated with neurological or cardiovascular issues.
The Heart Failure Contraindication
Following the SERVE-HF trial, ASV is strictly contraindicated for patients with symptomatic chronic heart failure who have a reduced Left Ventricular Ejection Fraction (LVEF ≤ 45%) and predominant Central Sleep Apnoea. In this specific population, ASV was shown to significantly increase cardiovascular mortality. A cardiology workup is often required before initiating ASV.