The word BiPAP is a proprietary term owned by Philips Respironics, but it has come into common usage to refer to any mode of CPAP that uses bi-level support. Other companies like may use terms such as VPAP by ResMed (variable positive airway pressure) or just bi-level by DeVilbiss to refer to the same type of therapy for sleep apnea and other disorders requiring respiratory support at night. We will use the terms interchangeably.

During inspiration, a BiPAP increases the pressure to push air in. This support on inspiration is sometimes referred to as IPAP (inspiratory positive airway pressure) or pressure support. During exhalation, the pressure drops to a lower level and stays there until the next inspiration. This lower level of exhalation pressure is sometimes called EPAP (expiratory positive airway pressure), PEEP (positive end expiratory pressure), or just CPAP.

BiPAP therapy may be recommended for patients with certain types of lung diseases to help them take in deeper breaths during sleep. Patients with unusual breathing patterns may also benefit from bi-level CPAP therapy. Patients with congestive heart failure may also breathe easier with BiPAP . Sometimes people who need a high level of pressure to overcome their obstructive sleep apnea find bi-level CPAP more comfortable than fixed pressure CPAP or auto CPAP.

The machines listed here only offer bi-level CPAP support for breaths that the patient initiates. Breaths that a patient initiates are referred to as spontaneous. Some bi-level machines have a timed function to support central apnea and other disorders that may benefit from the machine delivering an automatic inspiration at a fixed interval. Those machines are listed in our BiPAP ST/Adapt section .

BiPAP machines may provide fixed pressure bi-level CPAP or auto bi-level CPAP.

Fixed pressure bi-level CPAP: The machine generates a continuous pressure at the airway (CPAP). When the patient takes a breath, the machine detects that activity and increases the pressure to a fixed higher pressure. The increase in pressure creates a pressure differential and supports inspiration. In fixed pressure bi-level CPAP, the inspiratory pressure and expiratory pressures are constant values. If the inspiratory pressure is set at 15 and the expiratory pressure is set at 8, the machine always uses 15 and 8.

Auto bi-level CPAP: Similar to auto CPAP, the machine monitors the patient's breathing and moves the pressures up and down to resolve airway obstructions. Some bi-level machines also monitor the amount of air the patient inhales or exhales and adjust the pressure on inspiration to match a set volume ordered by the physician.

VPAP machines differ in size, range of noise output, and by the types of features they have for reducing potential complications and barriers to consistent, effective use. A BiPAP will be more in tune with the patient so many features that are optional on manual CPAP or auto CPAP machines are routinely present on bi-level machines. Bi-level devices also differ in what data they capture and how that data is stored and retrieved for use by you or by you and your physician.

A ramp setting creates a deliberate lag between the time when the machine is turned on and when the full prescribed pressure is delivered. The ramp gives the patient time to get in bed, read, watch TV, or do a crossword puzzle before the full flow starts. The intentional lag may make it easier to get to sleep.

A ramp feature is commonplace on bi-level machines but how it works varies by model. Some machines have a preset ramp time while other models let the patient set the timer. On some devices, the ramp phase may be gradual: the pressure initializes very low and rises incrementally over the set period. On other machines, the pressure stays dormant until the device detects an airway obstruction. The machine uses the detected obstruction as the signal to ramp up to the ordered pressure level.

Many BiPAP machines have flow shaping features to make the transition between the two different levels of pressure less abrupt. When a machine needs to move the pressure from 7 to 25, for example, it must increase the flow rate considerably. If the flow rate rises too rapidly, it can be jarring to the patient. Flow shaping allows the patient to breathe easier despite the flow and pressure changes.

Oral and nasal dryness, hoarseness, and nose bleeds are potential side-effects of any mode of CPAP therapy. Humidification can prevent or remedy these concerns. Heated humidifiers may be built into a machine or available for purchase separately. Without humidification, the flow from the machine tends to be cool and dry. Humidifiers warm up the air and saturate it with water vapor.

Some BiPAP machines maintain the humidity rate and air temperature at a fixed point, while others provide ambient monitoring and adjust the humidity and temperature level up or down to best meet the need in the moment. The dynamic adjustment helps reduce an effect known as “rain out,” which occurs when warm, humidified gas cools as it travels through the tubing to the patient. Some machines have heated tubing to help minimize condensation accumulation.

Humidifiers require sterile water. On some units, the user pours water into the humidifier. Other machines have detachable containers.

All bi-level equipment tracks some data regarding usage, but there is considerable variation in what information is recorded and monitored and how it is retrieved. Increasingly, machines use a wireless connection to upload data to the internet or a smartphone application. Devices that do not have a wireless connection may have data retrieval via an SD card or USB port. The data may include things like how often the machine was in use and whether the patient had obstructive or apneic events. You or your physician can look at the data to determine if the ordered parameters are working for you. Some machines integrate with smartphone applications both for data capture and sharing and for setting adjustments.

All BiPAP machines need a stable location near the bed with easy access to a power supply. The device should be flat and not jostled. The user must make sure the tubing reaches their bed space without difficulty. Longer hoses are usually available for purchase if needed. Bi-level CPAP machines pull air in from the room through a filter that removes dust and other particles. The filter needs to be replaced as recommended to prevent device obstructions and failures. The hose or tubing requires daily cleaning. The humidifier also requires cleaning and sterile water replenished.

Follow the manufacturer's recommendations for cleaning and part replacements. Adhering to the recommendations keeps the user healthy and prolongs the life of the machine.