For Machine purchases, your prescription should have the physician's information and signature, the type of machine you need (CPAP, Auto CPAP, or BiLevel), and the pressure at which the machine is to be set. Your doctor may also want include what type of humidification is recommended but this is not necessary.For Mask or Humidifier Purchases, your prescription should have the physician's information and signature, along with an order for CPAP Supplies. A prescription for a Machine is also valid for buying Masks and Humidifiers.