RT Journal Article SR Electronic T1 Principles of CPAP and auto-adjusting CPAP devices JF Breathe JO breathe FD European Respiratory Society SP 42 OP 50 VO 5 IS 1 A1 Farré, R. A1 Montserrat, J.M. YR 2008 UL http://breathe.ersjournals.com/content/5/1/42.abstract AB Educational aims To explain that the nocturnal events experienced by patients with OSAHS are caused by an abnormal increase in the collapsibility of the upper airway. To show that CPAP is an effective mechanical treatment for preventing upper airway obstruction and, therefore, normalising sleep in OSAHS patients. To outline the working principles of CPAP devices and to describe their practical performance. To describe the rationale and functioning of auto-adjusting CPAP devices for the treatment of OSAHS patients. Summary Obstructive apnoea–hypopnoea syndrome (OSAHS) is very prevalent. It causes a considerable reduction in patients' quality of life and induces important short- and long-term consequences, such as traffic accidents and cardiovascular diseases. The application of continuous positive airway pressure (CPAP) by means of a nasal mask is currently the most widespread and effective treatment for OSAHS. The present review article will address the following questions. • What is the physiological rationale of CPAP? • What are the principles of CPAP equipment? • How can we optimise its use? • What are auto-adjusting CPAP devices and how do they operate? • To what extent are they useful in the treatment of OSAHS?