An adapter (600) for connecting a ventilation hose (624) to a ventilator is described. The ventilation hose (624) comprises at least a hose inhalation conduit (628). The adapter comprises an adapter inhalation conduit (630) having a first end (602) arranged for connection to the hose inhalation conduit (628) of the ventilation hose (624) and a second end (606) arranged for connection to an inhalation gas supply of the ventilator. An adapter exhalation conduit (622) is provided having a first end (604) arranged for connection to a hose exhalation conduit (626) and a second end (608) openable to atmosphere. Means (638) are provided for closing the second end for providing a positive end expiration pressure. A flow sensor (616) is provided for generating a signal representing a flow of fluid arriving via the first end (604) of the adapter exhalation conduit (622).
