| Device |
Mechanism |
| Fixed CPAP |
A single pressure is set. The device attempts to maintain this during inspiration and expiration and throughout the period of use. |
| Automatically adjusting‐CPAP (auto‐CPAP) |
High and low pressure limits are set. The device adjusts its pressure within these limits to try to maintain a patent (clear and open) airway. The pressure does not vary between inspiration and expiration but will vary across the period of use. |
| Bilevel positive airway pressure (Bi‐PAP) |
Two pressure levels are set. The device aims to co‐ordinate with patient breaths to deliver the higher pressure throughout inspiration and the lower pressure throughout expiration. If the patient has no respiratory effort some machines will produce timed or back up breaths. |
| CPAP with expiratory pressure relief (CPAPexp) |
A basic pressure is set for the period of use. The device tracks patient effort and drops from the basic pressure by a preset amount at the start of expiration, increasing back to the basic pressure at the end of expiration. The pressure drops by 1 of 3 amounts selected according to patient comfort. |
| Heated humidification |
The addition of heated humidification to the CPAP circuit increases the humidity and temperature of inspired air; this aims to reduce dryness of the upper respiratory tract and improve comfort. |
| Auto‐CPAPexp |
This device combines the modalities of automatically adjusting continuous positive airway pressure and expiratory pressure relief. |
| Bi‐PAPexp |
This device combines the modalities of bilevel positive airway pressure and expiratory pressure relief. |
| Auto bi‐PAP with pressure relief |
This device reduces the pressure delivered at the end of inspiration and pressure during the early part of expiration, combined with an automatic titration modality. |
| CPAPexp with wakefulness detection |
This CPAP device with expiratory pressure relief incorporates a sensor to detect when the user is rousing from sleep. |
