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• A PAP machine that provides heated humidity has a chamber that must be filled with water every day or two. Adding heated humidity to the air helps reduce dryness in the nose , which can be especially useful in dry regions or during colder months.
• Pressure relief: A pressure relief feature allows medical providers to set up PAP machines so they deliver air at a slightly lower pressure when a sleeper begins to breathe out. This can reduce the discomfort that some people feel when exhaling while using a PAP machine.
• Pressure ramp: Like pressure relief, a pressure ramp feature may also reduce discomfort. This feature lets a sleeper start their machine at a lower air pressure, then the machine increases the pressure over the next 5 to 45 minutes. This gradual increase can help a person fall asleep more easily.

How Is APAP Different From CPAP?

While APAP and CPAP machines are both types of PAP therapy used to treat obstructive sleep apnea, they differ in the levels of air pressure they release. CPAP releases air at a fixed rate, while APAP releases air at a rate that changes in response to the sleeper’s needs.

Technically, an APAP is a type of CPAP machine that includes technology allowing the machine to auto-adjust how much air it delivers at a given time. Traditional CPAP machines that do not contain this technology are sometimes referred to as fixed-level CPAP devices, because they deliver air at a fixed rate of pressure. In the past, fixed-level CPAP machines were most commonly prescribed, but in recent years, the use of APAP machines is increasing .

An example of an APAP machine next to a CPAP machine.

Since APAP machines auto-adjust in response to a person’s breathing, the initial set-up can usually occur in a person’s home , using the machine itself. By contrast, the initial set-up of a fixed-level CPAP machine requires either an overnight sleep study in a lab or the temporary use of an APAP machine at home.

However, certain factors, such as suspected air leakages or the presence of other health problems, may require a person to have their APAP titration in a sleep lab rather than at home.

While some studies show that people tend to use an APAP machine longer each night than they would a CPAP machine, more evidence is needed to determine which type of machine is more effective at reducing OSA symptoms. Current research suggests both types of PAP therapy are about equally effective.

Another type of PAP therapy sometimes prescribed to people with OSA is bilevel positive airway pressure (BiPAP or BPAP). Doctors usually prescribe BiPAP only to people who have another sleep disorder or who have tried CPAP and APAP therapies but could not tolerate them.

Why Use an APAP Machine?

Using an APAP machine to treat obstructive sleep apnea may provide some advantages over other types of PAP therapy.

• In-home titration: While the set-up of BiPAP and fixed-level CPAP devices often requires an overnight stay in a sleep lab, an APAP device’s settings can be determined in a person’s home with the machine’s auto-adjusting feature.
• Reduced average air pressure: Some people find it uncomfortable to breathe out against the constant pressure of a fixed-level CPAP. Compared to a CPAP, an APAP machine releases air at a lower average pressure throughout the night, making it easier to handle for some users.
• Adjusting to users’ needs: An APAP machine’s ability to automatically adjust air pressure could benefit a person as their needs change at different times. For example, drinking alcohol, gaining or losing weight, and changing sleep positions can all alter the pressure level a sleeper needs from their PAP machine.