A continuous positive airway pressure (CPAP) machine is a simple respiratory ventilator used mainly by patients at home, for the treatment of sleep apnea. In sleep apnea, the patient's airway becomes restricted as their muscles relax naturally during sleep, which causes arousal from sleep. The CPAP machine stops this phenomenon by delivering a constant stream of compressed air via a mask, which splints the airway, allowing the patient to breathe freely. The CPAP machine blows air at one set pressure (called the titrated pressure), usually programmed into the machine by the sleep physiologist . The titrated pressure is an average reading from a titration study, and is usually measured in centimetres of water cm/H20.

Newer, more sophisticated models of CPAP machine are coming onto the market for home use, the most popular of which is the auto-titrating CPAP, also known as Intelligent CPAP (iCPAP), or AutoPAP (APAP). This type of machine uses a pressure sensor to enable the machine to alter the CPAP pressure on a breath-by-breath basis by measuring the resistance in the patient's breathing, thus giving the patient exactly the pressure they need at a given moment and avoiding the compromise of fixed pressure CPAP. The iCPAP usually has the capability to record a great deal of information which can be downloaded and analysed by a sleep physiologist to ensure the treatment is having the desired effect.

Currently auto-titrating CPAP machines cost around 3-4 times that of a conventional fixed pressure machine, but as manufacturing costs come down it is more than likely that this type of machine will become prevalent.