Comparison of pulmonary deposition of nebulized (99m)technetium‐diethylenetriamine‐pentaacetic acid through 3 inhalation devices in healthy dogs

BACKGROUND: Inhalation treatment frequently is used in dogs and cats with chronic respiratory disease. Little is known however about the performance of delivery devices and the distribution of aerosolized drugs in the lower airways. OBJECTIVE: To assess the performance of 3 delivery devices and the impact of variable durations of inhalation on the pulmonary and extrapulmonary deposition of nebulized (99m)technetium‐diethylenetriamine‐pentaacetic acid ((99m)Tc‐DTPA). ANIMALS: Ten university‐owned healthy Beagle dogs. METHODS: Prospective crossover study. Dogs inhaled the radiopharmaceutical for 5 minutes either through the Aerodawg spacer with a custom‐made nose‐muzzle mask, the Aerochamber spacer with the same mask, or the Aerodawg spacer with its original nose mask. In addition, dogs inhaled for 1 and 3 minutes through the second device. Images were obtained by 2‐dimensional planar scintigraphy. Radiopharmaceutical uptake was calculated as an absolute value and as a fraction of the registered dose in the whole body. RESULTS: Mean (±SD) lung deposition for the 3 devices was 9.2% (±5.0), 11.4% (±4.9), and 9.3% (±4.6), respectively. Differences were not statistically significant. Uptake in pulmonary and extrapulmonary tissues was significantly lower after 1‐minute nebulization, but the mean pulmonary/extrapulmonary deposition ratio (0.38 ± 0.27) was significantly higher than after 5‐minute nebulization (0.16 ± 0.1; P = .03). No significant differences were detected after 3‐ and 5‐minute nebulization. CONCLUSION AND CLINICAL IMPORTANCE: The performance of a pediatric spacer with a custom‐made mask is comparable to that of a veterinary device. One‐minute nebulization provides lower pulmonary uptake but achieves a better pulmonary/extrapulmonary deposition ratio than does 5‐minute nebulization.