Bilevel positive airway pressure (BiPAP) is a noninvasive therapy that delivers pressurized air through a mask into a person's airways. A BiPAP machine has a higher pressure setting for when the patient inhales and a lower pressure setting for when the patient exhales. BiPAP machines are used to treat patients with sleep apnea, and they have been investigated as a noninvasive treatment for patients with cancer who have dyspnea.