A consists of a single pressure setting that stays the same all night long. Many of these models are equipped with a ramp feature, which starts the machine out on a low-pressure setting and then gradually increases throughout the night. Once the reaches the prescribed pressure setting, it will stay there for the remainder of the evening. Many users prefer a model with a ramp feature because the starting pressure is much more gentle as opposed to an immediate high-level burst, which can be overwhelming for some people.
