Abstract: A valve for directing flow of breath to and from a patient has a first port adapted to be connected to a source of breath, a second port adapted to be connected to a patient and first obturating means in the form of a diaphragm for controlling flow between the first and second ports. A passage in the valve is in continuous communication with the second port through apertures in the diaphragm and second obturating means formed by a further diaphragm controls flow from the second port through the passage. The further diaphragm is arranged to prevent flow through the passage when the first-mentioned diaphragm is allowing flow between the first and second ports.