What is Positive Airway Pressure (PAP)?

There are three types of positive airway pressure (PAP) machines used to treat sleep apnea.

These sleep apnea machines look similar, but differ in the way they moderate the flow of air:

  • Continuous Positive Airway Pressure (CPAP) or
  • Automatic Positive Airway Pressure (APAP) or
  • Variable Positive Airway Pressure (VPAP), also known as BiLevel (BiPAP)

In terms of usage, CPAP and APAP are the most common sleep apnea machines with VPAP being used as therapy for some sleep apnea patients or to treat other respiratory diseases.

CPAP & APAP devices work by delivering a gentle flow of air to the back of your throat using a mask, this flow of air creates positive air pressure which forms an air splint that stops your airway from collapsing. Similarly, to CPAP and APAP devices the VPAP machines also creates an air splint, but provides additional support during exhalation.


The key differences between CPAP and APAP

CPAP & APAP are generally used as sleep apnea machines, whereas VPAP can be used to manage other respiratory disorders in addition to sleep apnea. The key differences between these machines is the way they keep your airways open by either producing a continuous, automatically-regulated or variable positive air pressure.


CPAP delivers one level of pressure continuously throughout the night.
This pressure will not change unless it is updated by a sleep technician or doctor.
An overnight sleep test in a laboratory is required to determine and setup the correct air pressure for sleep apnea therapy. You will be required to revisit the sleep lab up to four times a year to make sure your pressure levels are correct.


APAP machines automatically adjusts the pressure using an algorithm. The algorithm senses when your body is about to have an event and automatically adjusts the pressure depending on how severe the event is to keep your airways open.

Unlike CPAP devices, with APAP machines you will not need to go to a sleep lab overnight to determine the correct pressure for therapy – it is automatically calculated.

An APAP device will also accommodate other environmental factors, such as if you drink any alcohol before bed (which can make your sleep apnea worse).


VPAP is also automated using an algorithm. In addition to blowing out a gentle stream of air, it will also help you exhale. VPAP is only suitable for some patients and should be considered under the guidance of your sleep physician or doctor.

Getting treated for sleep apnea using either CPAP / APAP sleep apnea machines can help reduce other serious health issues. With the right support, many patients begin to feel relief from some symptoms after a few days of treatment.




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