A VPAP machine is a breathing device that delivers two different levels of air pressure to keep your airway open while you sleep. VPAP stands for variable positive airway pressure, and it’s ResMed’s brand name for what’s more broadly known as bilevel or BiPAP therapy. The “variable” part means the machine switches between a higher pressure when you breathe in and a lower pressure when you breathe out, making it easier and more comfortable to exhale against the airflow.
How a VPAP Machine Works
A VPAP delivers air through a mask fitted over your nose or nose and mouth, just like a standard CPAP. The key difference is in how it manages pressure. A CPAP pushes air at one constant pressure all night long. A VPAP uses two distinct pressure settings: one called IPAP (the higher pressure during inhalation) and one called EPAP (the lower pressure during exhalation).
When you inhale, the machine ramps up to the higher pressure, helping to splint your airway open and pull air deeper into your lungs. When you exhale, the pressure drops to the lower setting, so you’re not fighting against a wall of air on the way out. This cycling happens automatically with each breath. Typical EPAP settings fall between 4 and 6 cm H₂O, while IPAP settings generally range from 10 to 20 cm H₂O, though your prescribing provider will set these based on a sleep study or titration.
The Backup Rate Feature
Some VPAP machines include a timed backup rate, often labeled as “ST” (spontaneous/timed) mode. This feature is important for people who occasionally stop making the effort to breathe during sleep. If the machine detects that you haven’t taken a breath within a set window, it automatically delivers a breath for you at the higher pressure. The backup rate is typically set about two breaths per minute below your natural resting breathing rate, with a common starting point around 15 breaths per minute. During a central apnea, where your brain temporarily stops signaling your muscles to breathe, the backup rate kicks in and ventilates you until spontaneous breathing resumes.
Who Benefits From a VPAP
VPAP therapy is prescribed for a wider range of breathing problems than a standard CPAP. The most common reasons include:
- Obstructive sleep apnea that hasn’t responded well to CPAP, or where CPAP feels intolerable because of the constant pressure on exhalation
- Central sleep apnea, where the brain intermittently fails to trigger a breath
- Complex sleep apnea, a combination of obstructive and central events that can emerge or persist during CPAP therapy
- COPD and other chronic lung diseases that cause carbon dioxide to build up in the blood because the lungs can’t ventilate effectively
- Heart failure, where fluid congestion in the lungs makes breathing harder during sleep
For complex sleep apnea specifically, advanced bilevel devices with adaptive algorithms have shown strong results. In a controlled trial, about 90% of patients using adaptive servoventilation (a more advanced form of bilevel therapy) achieved an acceptable breathing score after 90 days, compared to roughly 65% of those on CPAP alone. That means about a third of complex sleep apnea patients remain inadequately controlled on CPAP, which is one of the main reasons providers step up to bilevel therapy.
VPAP vs. CPAP vs. BiPAP
The terminology can be confusing because these devices overlap. CPAP is the simplest option: one fixed pressure, all night, every breath. BiPAP (or BPAP) is the general term for any bilevel device that provides two pressures. VPAP is simply ResMed’s trademarked name for their bilevel machines. Functionally, a VPAP and a BiPAP from another manufacturer do the same thing.
Some newer VPAP models go further by incorporating volume-targeting technology. Instead of locking in a fixed higher pressure, the machine automatically adjusts the inhalation pressure breath by breath within a preset range (for example, 7 to 25 cm H₂O) to make sure each breath delivers a target volume of air. This is particularly useful for people whose breathing effort fluctuates throughout the night, such as those with neuromuscular conditions or severe COPD.
What Using a VPAP Feels Like
If you’ve tried CPAP and found it hard to breathe out against the pressure, a VPAP will likely feel like immediate relief. The pressure drop on exhalation is noticeable. Most people describe the sensation as more natural, closer to how breathing feels without a machine. The mask options are the same as CPAP: nasal pillows, nasal masks, or full-face masks, depending on whether you breathe through your mouth at night.
Average nightly usage on bilevel devices tends to mirror CPAP. In clinical studies, patients on both types of therapy averaged about 4.5 to 4.7 hours of use per night, and reported similar improvements in daytime sleepiness and quality of life. The advantage of VPAP isn’t necessarily that people wear it longer, but that it controls breathing events more effectively in patients who need more than a single pressure level.
Safety Considerations
VPAP therapy is safe for the vast majority of people it’s prescribed to, but certain conditions require caution. People who have had recent surgery on their airway or digestive tract should not use positive pressure devices until healed. Those with difficulty protecting their airway, frequent vomiting, or excessive mucus production may not be good candidates.
For heart failure patients, VPAP is generally beneficial, but providers use extra care in specific situations: severe right-sided heart failure with liver congestion, hypertrophic obstructive cardiomyopathy, or severe aortic valve disease. In these cases, the pressure changes can reduce blood flow returning to the heart in ways that worsen symptoms rather than help. Patients with very unstable blood pressure or cardiogenic shock are also typically not started on pressure therapy until they’re stabilized.