A speaking valve 7 moveable between a first configuration (Fig 15A) allowing for inspiration and expiration through the valve, and a second configuration in which expiration is resisted. Increasing the pressure difference across the valve by increasing the rate of expiration to a pre-determined threshold causes the valve to transition into the second configuration. In the second configuration the valve continues to resist expiration until a predetermined negative pressure difference across the valve causes it to transition back into the first configuration. The valve may comprise a bistable diaphragm 14, with the diaphragm interacting with a valve seat 18 to resist flow through the valve in one of its two stable configurations, said stable configuration corresponding to the second configuration of the valve. Such a valve may be used as part of an airway management device.
