What is the difference?

CPAP stands for continuous positive airway pressure. BiPAP refers to Bilevel or two-level positive airway pressure. BiPAP is a trademark of Respironics.
While CPAP generally delivers a single pressure, BiPAP delivers an inhale pressure and an exhale pressure.

Which is better?

Each is used for a special purpose. Historically, BiPAP was more expensive than CPAP. BiPAP is often used when CPAP is not tolerated by the user. There are new technologies that increase comfort with CPAP.

BiPAP is sometimes used in patients who have pulmonary (lung) issues, like COPD. The difference in pressures helps to eliminate extra CO2 carbon dioxide gas from the body.

CPAP and BiPAP machines look similar. The attachments are the same.

There are other type of ventilatory support devices, including Adaptive Servo Ventilation (ASV).

ASA is sponsored by Philips and has received funding from them.

CPAP Masks

CPAP, BiPAP, ASV Machines


Philips DreamCPAP



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The CPAP machine is designed to deliver air pressure through the nostrils into the back of the throat in order to keep the airway open. The pressure is adjustable. There are several potential modifications to the way the air can be delivered in order to keep the airway open during sleep.

The BiPAP or bilevel machine is very similar to the C-PAP machine. Utilizing the identical setup as a CPAP with tubing and masks, the BiPAP uses a different pressure setting. While CPAP delivers one pressure, BiPAP delivers two pressures. These two pressures are known as inhalation positive airway pressure (IPAP) and exhalation positive airway pressure (EPAP).

BiPAP is often used with individuals who need extra respiratory support. It is often prescribed for patients with congestive heart failure/coronary artery disease and pulmonary or neurologic medical disorders. Patients with neuromuscular disorders may also benefit from the pressure differential of a bilevel positive airway pressure device.

The BiPAP is usually preset with two settings. The effort when inhaling and exhaling is monitored. When the  person sleeping doesn’t breathe for a programmed period of time, the BiPAP may be set to deliver a breath. This is usually set as a minimum breath or ‘back-up rate’ that sets a minimum breaths per minute (BPM).

This setting is designed so that the patient breathes a set frequency of breaths per minute. One of the many  advantages of the BiPAP machine is that the strain is decreased during expiration. This limits the amount of energy expended during exhalation. In other words, it is easier to breathe out with BiPAP than with CPAP.

New BiPAP machines are similar in size to CPAP devices. They are about the size of a lunchbox. Many are very quiet. They’re designed to be silent so as not to interrupt the sleeper. Most BiPAP units offer a humidifier option to prevent the drying of the mucosal membranes.

In summary, the primary difference between CPAP and BiPAP, or bilevel, machines is the pressure differential. While CPAP has one pressure. BiPAP has two pressures. The ordering sleep physician usually decides what type of breathing treatment should be used. A sleep study often aids in the decision making of this process.

BiPAP is a trademark of Respironics and is a promotional partner of ASA.

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