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 it…in 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.
