An electronically actuated in-line droplet delivery device for delivering a fluid as an ejected stream of droplets to the pulmonary system of a subject, the device comprising: a housing configured in a substantially in-line orientation; a mouthpiece positioned at an airflow exit of the device and in-line or parallel with the housing; one or more airflow entrances on one or both of opposite exterior sides of the device; an air inlet flow element positioned in the airflow at each airflow entrance of the device; a reservoir disposed within or in fluid communication with the housing for receiving a volume of fluid; an electronically actuated ejector mechanism in fluid communication with the reservoir and configured to generate the ejected stream of droplets; at least one differential pressure sensor positioned within the housing, the at least one differential pressure sensor configured to activate the ejector mechanism upon sensing a pre-determined pressure change within the mouthpiece to thereby generate the ejected stream of droplets; the ejector mechanism comprising a piezoelectric actuator and an aperture plate, the aperture plate having a plurality of openings formed through its thickness and the piezoelectric actuator operable to oscillate the aperture plate at a frequency to thereby generate the ejected stream of droplets; wherein the housing, the one or more air inlet flow elements, and the mouthpiece are configured to facilitate non-turbulent airflow across an exit side of the aperture plate and to provide sufficient airflow through the housing during use; and wherein the ejector mechanism is configured to generate the ejected stream of droplets wherein at least about 50% of the droplets have an average ejected droplet diameter of less than about 6 microns, such that at least about 50% of the mass of the ejected stream of droplets is delivered in a respirable range to the pulmonary system of the subject during use. a housing configured in a substantially in-line orientation; a mouthpiece positioned at an airflow exit of the device and in-line or parallel with the housing; one or more airflow entrances on one or both of opposite exterior sides of the device; an air inlet flow element positioned in the airflow at each airflow entrance of the device; a reservoir disposed within or in fluid communication with the housing for receiving a volume of fluid; an electronically actuated ejector mechanism in fluid communication with the reservoir and configured to generate the ejected stream of droplets; at least one differential pressure sensor positioned within the housing, the at least one differential pressure sensor configured to activate the ejector mechanism upon sensing a pre-determined pressure change within the mouthpiece to thereby generate the ejected stream of droplets; the ejector mechanism comprising a piezoelectric actuator and an aperture plate, the aperture plate having a plurality of openings formed through its thickness and the piezoelectric actuator operable to oscillate the aperture plate at a frequency to thereby generate the ejected stream of droplets; wherein the housing, the one or more air inlet flow elements, and the mouthpiece are configured to facilitate non-turbulent airflow across an exit side of the aperture plate and to provide sufficient airflow through the housing during use; and wherein the ejector mechanism is configured to generate the ejected stream of droplets wherein at least about 50% of the droplets have an average ejected droplet diameter of less than about 6 microns, such that at least about 50% of the mass of the ejected stream of droplets is delivered in a respirable range to the pulmonary system of the subject during use.