Pressure while machine is titrating between ipap and epap-pressure support should be selected by the physician. bilevel cpap machines - commonly referred to as bipap machines - provide the most flexibility with regard to exhalation pressure relief. a bilevel cpap system delivers two different positive pressure levels - an inspiratory positive airway pressure, or ipap, and an expiratory positive airway pressure, or epap. the difference between these two pressure levels is commonly referred to as the pressure support.this type of pressure relief is similar to pressure relief technologies like c-flex, epr, and softx, with the primary difference being that the pressure support on a bilevel cpap machine can be much higher. that is, the difference between the ipap and epap on a bilevel machine can be much greater than the difference you might experience using one of the aforementioned pressure relief technologies.