The acronym (CPAP) stands for continuous positive airway pressure. CPAP is used to treat sleep apnea patients, who have upper airway obstruction. Bilevel positive airway pressure (BiLevel), is similar to CPAP therapy however BiLevel therapy is used to treat more than just sleep apnea. The bilevel machine is able to detect how much pressure a patient needs and supply the adequate amount of air pressure on inhalation and exhalation.