The most common treatment for OSA has been the use of a continuous positive air pressure (CPAP) machine. Many patients find that they cannot, or choose not to wear the CPAP, and therefore choose the risks associated with OSA. Sometimes the removal of either the excess palatal tissue or the uvula has been performed as a treatment option. The American Sleep Disorder Association (ASDA) has endorsed oral appliance therapy as the third currently acceptable treatment for snoring and sleep apnea. For cases of mild to moderate OSA, a oral appliance will be the treatment of choice. In severe cases of OSA, a CPAP is the preferred treatment. The oral appliance may then be used to use less air pressure with the CPAP (or instead of the CPAP if the patient cannot or refuses to wear the CPAP).