CPAP guide

CPAP or BiPAP? The differences simply explained

CPAP, auto-CPAP, BiPAP and ASV – the terms are often mixed up. Here we explain how these devices work technically. Which type of device is suitable is always decided by your doctor or sleep lab.

FR

Author: Farshad Raisiyan – Managing Director, Desstronic UG
B.Sc. Electronics, M.Sc. Mechatronics. In 2018 he led research & development of a turbine-driven surgical ventilator, from concept and engineering prototype to technical documentation and the CE conformity process. At Desstronic he tests used CPAP and BiPAP devices: pressure and flow measurement, noise and vibration checks, device documentation.
Updated: 19 October 2026. Technical information, not medical advice.

CPAP: one constant pressure

CPAP stands for “Continuous Positive Airway Pressure”. The device delivers a constant positive pressure during inhalation and exhalation, stated in cm H₂O (or hPa). The pressure value is set by your doctor.

Auto-CPAP (APAP): pressure within a range

An auto-CPAP device such as the ResMed AirSense 10 AutoSet adjusts the pressure itself – but only within a range that your doctor has set with a minimum and maximum pressure. The technical range of the AirSense 10 is 4 to 20 cm H₂O.

EPR: expiratory relief on CPAP

Many ResMed CPAP devices offer EPR (Expiratory Pressure Relief), which slightly lowers the pressure during exhalation. It is still a CPAP device – a BiPAP device works with two separately set pressure levels. Whether EPR is enabled is decided by your provider.

BiPAP or bilevel: two pressure levels

A bilevel device uses a higher pressure for inhalation (IPAP) and a lower one for exhalation (EPAP). The difference is called pressure support. “BiPAP” is a widely used name, “bilevel” the general term.

Modes, using the ResMed AirCurve 10 as an example

S (spontaneous): the device switches between IPAP and EPAP as soon as it detects your own inhalation or exhalation.
ST (spontaneous/timed): like S, plus a set backup rate.
VAuto: automatically adjusts the pressure values within set limits.
CS PaceWave (ASV): adaptive servo-ventilation that adjusts support breath by breath. ASV has specific contraindications and is only used after medical assessment.

Overview

CPAP: one fixed pressure – e.g. AirSense 10 Elite.
Auto-CPAP: automatic within a set range – e.g. AirSense 10 AutoSet, prisma SMART.
BiPAP / bilevel: two levels (IPAP/EPAP) – e.g. AirCurve 10 S, ST, VAuto.
ASV: variable, breath by breath – e.g. AirCurve 10 CS PaceWave.

All of them are used only on prescription and with settings made by your doctor, sleep lab or provider.

Devices in the shop

CPAP devices are in our CPAP category, bilevel and ASV devices under ventilators & BiPAP.

Frequently asked questions

What is the difference between CPAP and BiPAP?

CPAP delivers one constant pressure; BiPAP (bilevel) uses two separate pressure levels for inhalation (IPAP) and exhalation (EPAP).

Is EPR the same as BiPAP?

No. EPR slightly lowers the pressure during exhalation on a CPAP device. A BiPAP device has two independently set pressure levels.

Can I choose between CPAP and BiPAP myself?

No. The type of device and its settings are decided by your doctor or sleep lab.

What do IPAP and EPAP mean?

IPAP is the inspiratory (inhalation) pressure, EPAP the expiratory (exhalation) pressure of a bilevel device.

We do not replace medical advice. Only change therapy pressure and settings as prescribed by your doctor.

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Desstronic UG

Research, development & prototyping in electronics and mechatronics.
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