Apparatus for the administration by inhalation of radioactive particles to human subjects for studies of deposition and clearance

An apparatus is described for the administration of radioactive aerosols to human subjects by inhalation. It is used in studies of total and regional deposition. Separation of inhaled and exhaled airstreams is effected automatically by a solenoid driven valve operated by a pressure transducer responding to the small pressure changes in the mouthpiece caused by the subject's breathing. The respiratory rate and tidal volume of the subject are recorded. Techniques used for the estimation of the amount of aerosol inhaled and exhaled are described. Factors affecting the decay of aerosol concentration in the chamber and their effect on the maximum particle size which can be usefully employed in the apparatus are discussed. (author)