CPAP success usually means Obstructive Sleep Apnea. Continuous Positive Airway Pressure devices use air to blow the obstructions out of the way. It usually requires a sleep lab test to get a CPAP prescribed. Sometimes, an at home test will be done first if your insurance company is cheap and needs pre-auth. Then, a sleep lab test is done to test out the effectiveness of a CPAP. Many go straight to the sleep lab and get a CPAP fitted during the night after observing OSA. There are many permutations of how the system works depending on insurance and local preferences.