CPAP and BiPAP machines treat sleep apnea, a condition that causes a person's breathing to become shallow or stop temporarily while asleep. The lack of oxygen often causes the individual to snore loudly, wake up with a dry mouth, and feel exhausted during the day. It can also lead to high blood pressure, and in extreme cases, a heart attack or stroke.There are three main types of sleep apnea. The most common form is obstructive sleep apnea, which occurs when throat muscles relax, closing the upper airway during sleep. The other primary forms are central sleep apnea and complex sleep apnea syndrome. The former occurs when your brain doesn't send the necessary signals to your muscles that are needed to control breathing. Complex sleep apnea (or treatment-emergent central sleep apnea) occurs when both of the other two forms appear simultaneously. CPAP and BiPAP machines both work to stabilize the flow of air while sleeping. For both products, users wear a mask that provides a constant flow of pressurized air that prevents the soft palate, tongue and uvula from blocking the airway. A CPAP machine provides higher air pressure when you exhale, and a BiPAP provides higher pressure air when you inhale. Your health care provider will determine the best option based on your unique situation and medical history.