ADMINISTRATION of a therapeutic agent by inhalation of its aerosol is an established procedure. Some medicinal aerosols, particularly wetting or humidifying agents, must be administered into a tent continuously for many hours or even several days for complete and effective therapy.
Many difficulties attend the use of ordinary methods of prolonged aerosol administration. The nebulizers in common use have a maximum capacity of only about 10 cc. of liquid; so an automatic and continuous source of additional liquid is required. This is achieved, basically, by inserting a needle through the side stopper of a nebulizer and dripping the therapeutic solution from a clysis bottle into the nebulizer through this needle.
This method is simple and would be ideal except that the fluid level is utterly impossible to control. No matter how carefully the rate of drip is measured, the nebulizer will either run dry or overflow ("rain") onto the patient
MILLER JB. APPARATUS FOR PROLONGED CONTINUOUS AEROSOL ADMINISTRATION. AMA Am J Dis Child. 1952;84(5):616-621. doi:10.1001/archpedi.1952.02050050090006