technetium-tc-99m-sulfur-colloid and Airway-Obstruction

Aerodynamic forces provide the primary means of distributing aerosol medications within the lungs. Partial airway obstructions can limit both air flow and aerosol penetration into diseased zones. We hypothesize that low surface tension additives may help to disperse aerosol medications after deposition in the airways, improving dose uniformity and drug delivery to underventilated regions. To test this, we performed a pilot scintigraphy study of surfactant and saline deposition and postdeposition dispersion.. Because inhaled antibiotics for cystic fibrosis provide an example of where self-dispersing medications may be useful, we administered calfactant and saline aerosols with added Technetium 99m sulfur colloid (Tc-SC; 100 nm filtered) on different days in randomized order to eight cystic fibrosis (CF) subjects (average FEV(1)%, p=85 ± 12%). Nebulized delivery was matched (similar aerosol sizes and volume delivery rates, fixed breathing patterns). Tc-SC distribution in the lungs was imaged continuously for 30 min after delivery.. Both aerosols were well tolerated. Aerosol distribution was mostly peripheral (58/42%) and initially similar for saline and surfactant. Changes in whole lung counts after 30 min were also similar. Peripheral lung activity decreased more rapidly on average with calfactant though the difference versus saline was not statistically significant. Central to peripheral count ratio decreased with saline and increased with calfactant and c/p changes approached significance (-0.05 ± 0.16 vs. 0.10 ± 0.10; p=0.07 Wilcoxon).. Our results lack statistical significance, but suggest that inhaled calfactant increased peripheral clearance, due to either surfactant-based dispersion or mucociliary effects. Further studies are needed to define the potential for low surface tension carriers to improve drug delivery.

Topics: Administration, Inhalation; Adult; Aerosols; Airway Obstruction; Biological Products; Cystic Fibrosis; Drug Delivery Systems; Female; Humans; Lung; Male; Middle Aged; Nebulizers and Vaporizers; Particle Size; Pilot Projects; Pulmonary Surfactants; Radionuclide Imaging; Technetium Tc 99m Sulfur Colloid; Time Factors; Young Adult

The use of single photon emission computed tomography (SPECT) and radiolabeled aerosols for lung scanning offers theoretical advantages over conventional gamma camera imaging. We verified the feasibility of using such a system to define particle deposition. First, in two dogs, we detected segments of the lung which had received fewer radiolabeled particles because of obstruction to the airway by a balloon or a lead shot. Second, by comparing axial computed tomography (CT) images to their SPECT counterparts, we were able to demonstrate the effectiveness of SPECT in delineating large thoracic structures such as major vessels and central airways. We feel that SPECT also provides excellent images for qualitative work. We then used SPECT to study aerosol deposition in 13 normal subjects and eight patients. We found that the normal subjects had uniform peripheral deposition, but the eight with abnormal lung function had patchy deposition. Furthermore, we found that regions of abnormal deposition not seen on conventional views could be delineated by tomography. We conclude that this technique will improve our understanding of aerosol deposition in humans by providing a three-dimensional visualization of the lungs and airways.

Topics: Aerosols; Airway Obstruction; Animals; Dogs; Humans; Injections, Intravenous; Lung; Particle Size; Pulmonary Ventilation; Technetium Tc 99m Aggregated Albumin; Technetium Tc 99m Sulfur Colloid; Tomography, Emission-Computed