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Bilevel positive airway pressure (BPAP)

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Bilevel positive airway pressure (BPAP), Variable positive airway pressure (VPAP), or bilevel is a continuous positive airway pressure (CPAP) mode used during noninvasive positive pressure ventilation. Bilevel refers to two pressures delivered for every breath cycle; an inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP). Pressure Support (PS) is the difference between IPAP pressure and EPAP pressure. BPAP can be described as a Continuous Positive Airway Pressure system with a time-cycled change of the applied CPAP level. CPAP, BPAP and other non-invasive ventilation modes have been shown to be effective management tools for chronic obstructive pulmonary disease and acute respiratory failure.

Often BPAP is incorrectly referred to as "BiPAP". BiPAP® is the name of a portable ventilator manufactured by the Philips-Respironics Corporation; it is just one of many ventilators that can deliver BPAP.

VPAP® is a trademark for bilevel capable portable ventilators manufactured by ResMed, Inc.

Modes of BPAP

S (Spontaneous) – In BiPAP-S or VPAP-S mode the device triggers IPAP when flow sensors detect spontaneous inspiratory effort and then cycles back to EPAP. BiPAP-S or VPAP-S refers to fixed pressure bilevel machines with no backup rate.
Auto (Spontaneous) - The BiPAP Auto or Vauto bilevel uses a pressure range for EPAP and IPAP (or EPAP plus PS). Like Auto-CPAP, these machines can raise pressure within the set range to respond to flow limitation, snores, obstructive apnea and hypopnea.
T (Timed) – In timed mode the IPAP/EPAP cycling is purely(machine-triggered, at a set "backup rate", typically expressed in breaths per minute (BPM).
S/T (Spontaneous/Timed) – Like spontaneous mode, the device triggers to IPAP on patient inspiratory effort. But in spontaneous/timed mode a "backup" rate is also set to ensure that patients still receive a minimum number of breaths per minute if they fail to breathe spontaneously.
ASV (Adaptive Servo Ventilator) – A considerably more complicated mode. It combines some of the features of S/T mode with a rapid increase in the pressure support to induce a breath, or a larger breath if the patient's respiratory rate decreases or respiratory volume decreases. ASV provides a continuous EPAP pressure that prevents obstructive apnea, and variable pressure support as needed, when needed to resolve hypopnea, central apnea and periodic breathing. The newest ASV machines have an Auto mode that can increase EPAP to prevent obstructive apnea or decrease EPAP when the airway is patent.
AVAPS/iVAPS (Average Volume Assured Pressure Support/Intelligent Volume Assured Pressure Support) is another advanced mode somewhat like ASV, but more tailored for patients with hypoventilation.

The distinction between "bilevel" and other classes of CPAP machines or ventilators is not always clear cut and may vary depending on where it is used. The particular term used may be chosen for insurance or administrative reasons rather than strictly technical reasons.

Some machines classified as CPAP or APAP provide Exhalation pressure relief, which is a limited form of what is technically bilevel. For insurance and administrative reasons, these machines are almost never referred to as "bilevel" machines.

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