Abstract: The present invention provides a breath-actuated inhalation device comprising: an aerosol generator comprising a vibrator and a membrane; and a reservoir for liquid to be aerosolized which is in fluid communication with the membrane. A method for operating the device is also provided. The vibrator is driven intermittently so that the aerosol generator has periods of aerosol generation during a patients inhalations and periods of little or no aerosol generation preceding and/or succeeding the inhalations Scans are performed in which an electrical parameter of the vibrator is measured as the membrane is vibrated at a plurality of frequencies. The spectrum obtained from a scan during an inhalation is compared with a spectrum obtained from a scan during the period preceding or succeeding that inhalation in order to determine whether liquid is present in the reservoir.

Abstract: The present invention provides a vibrating membrane nebulizer with an aerosol generator comprising a vibrator and a membrane, a reservoir for liquid to be aerosolized, a channel and an optical sensor for detecting the presence of aerosol in the channel. The device determines whether aerosol is present in the channel on the basis of the output signal from the optical sensor, in order to detect when the reservoir becomes empty, and stops vibration of the membrane if it determines that no aerosol is present. A method for operating the device is also provided.