PERFLUOROCARBON COMPOUND AEROSOLS FOR DELIVERY TO THE LUNG AS POTENTIAL F-19 MAGNETIC-RESONANCE REPORTERS OF REGIONAL PULMONARY PO(2)

RATIONALE AND OBJECTIVES. Perfluorocarbon (PFC) aerosols present the o pportunity for simultaneous analysis of lung structure and pulmonary o xygenation patterns. The authors investigated techniques to nebulize n eat liquid PFCs for inhalation as a new method of PFC administration a nd tested the hypothesis that PFC aerosols may be developed for effici ent delivery to the lung in an experimental rat model allowing the pot ential for sequential monitoring of pulmonary status via quantitative fluorine-19 (F-19) magnetic resonance (MR) partial pressure of oxygen (pO(2)) imaging. METHODS. Pneumatic aerosol generators were configured to produce a neat liquid PFC perfluorotributylamine (FC-43) aerosol, Perfluorocarbon inhalation breathing protocols for the rat model inclu ded: spontaneous direct breathing from an aerosol chamber, and use of a tracheotomy tube to bypass nasal breathing. The PFC aerosol delivery into the rat lung was documented through F-19 MR imaging in correlati on with high-resolution anatomic proton MR images. Theoretical model c alculations for PFC mass deposition were compared with experimental re sults. RESULTS. The pneumatic generator produced a PFC aerosol droplet within the theoretically targeted range (geometric mean particle diam eter of 1.2 mu m; concentration of similar to 4 x 10(7) droplets per c m(3)). No measurable aerosol reached the lungs during spontaneous brea thing because of the efficient filtering capabilities of the turbinate d nasal passages. With tracheotomy, aerosol depositions within the lun g were achieved in mass quantities consistent with theoretical expecta tions; however, the distribution patterns were nonuniform and unpredic table, Oxygen-enhanced F-19 imaging was demonstrated. CONCLUSIONS. Per fluorocarbon aerosols of controlled size distribution can be produced at sufficient concentration with pneumatic generators for distribution to the terminal pulmonary architecture and visualization using F-19 M R imaging. The potential exists for in vivo oxygen-sensitive imaging i n the pulmonary system and development of sophisticated experimental a nimal models of systemic oxygen transport as a function of pulmonary s tatus.