PAP Variations

CPAP stands for Continuous Positive Airway Pressure. There are several modifications to basic CPAP machines, including automatic adjusting PAP machines, bilevel PAP machines, and expiratory pressure decrease. What do all of these mean?

Automatic adjusting PAP (also called Autoset) means the machine varies the pressure while the PAP is being used. Standard CPAP machines do not do this. They are set to one pressure. The automatic PAP machine uses brand-specific methods to identify if the pressure that is being delivered to the patient is working or not. If the machine senses that the pressure is too low, it will increase the pressure until it determines that the sleep disordered breathing is under control. The machine does this throughout the night. Why is this beneficial? For most people it does not make a difference. However, some people have a variable pressure needs in different stages of sleep or body positions, while other people have different pressure needs on different nights. Some people simply find this more comfortable than a single pressure.

Bilevel machines allow your physician to set 2 different pressures instead of just one. An inspiratory pressure (also called IPAP, the pressure the machine delivers when you are breathing in) and an expiratory pressure (also called EPAP, the pressure the machine delivers when you breathe out) are set. What is the benefit of 2 pressures? Often when very high pressures are needed to control the sleep apnea (over 20 cm H2O), the CPAP is not well tolerated because people have difficulty exhaling. By setting an expiratory pressure that is lower than the inspiratory pressure, many people find it easier to breathe and therefore more comfortable.

An expiratory decrease machine (also called C-flex) is similar to bilevel PAP. With this mode, the pressure is allowed to decrease during exhalation by a small amount. This is different from bilevel PAP, because the physician still only sets one CPAP pressure and large differences in the pressure are not possible. This mode is more comfortable for some people since exhalation is easier.