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

Abstract

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.

Keywords: dog; inhalation; lung; radiopharmaceutical; scintigraphy.

FIGURE 1

Diagram of the equipment used for the administration of nebulized ^99mTc‐DTPA. A, PARI Master compressor; B, lead protective layer; C, PARI LL nebulizer; D, spacer; E, silicon mask; F, custom‐made nose‐muzzle mask. ^99mTc‐DTPA, ^99mtechnetium‐diethylenetriamine‐pentaacetic acid

FIGURE 2

Aerosol devices used for delivery of nebulized ^99mTc‐DTPA. Parts are depicted from left to right: A, Custom‐made nose‐muzzle mask + pediatric silicon mask + Aerodawg spacer; B, Custom‐made nose‐muzzle mask + Aerochamber plus facemask and spacer (child‐medium); C, Aerodawg nose mask and spacer. ^99mTc‐DTPA, ^99mtechnetium‐diethylenetriamine‐pentaacetic acid

FIGURE 3

Ventrodorsal 2D scintigraphic lung scans of dogs 2, 3, 4, and 7 after 5‐minute nebulization of ^99mTc‐DTPA through the Aerodawg nose‐muzzle mask (AeroD NM‐mask), Aerochamber plus nosemuzzle mask (AeroC NM‐mask), and Aerodawg nose mask (AeroD nose mask) devices. Esophagus uptake was removed to avoid interference with the pulmonary uptake [blank areas in scans (D), (F), (I), (J), (K), (L)]. ^99mTc‐DTPA, ^99mtechnetium‐diethylenetriamine‐pentaacetic acid

FIGURE 4

Ventrodorsal 2D scintigraphic lung scans of dogs 6, 7, 8, and 10 after 1‐, 3‐, and 5‐minute nebulization of ^99mTc‐DTPA through the Aerochamber plus nose‐muzzle mask device. Esophagus uptake was removed to avoid interference with the pulmonary uptake [blank areas in scans (B), (E), (F), (H), (K)]. ^99mTc‐DTPA, ^99mtechnetium‐diethylenetriamine‐pentaacetic acid

FIGURE 5

Whisker box plot of nebulized ^99mTc‐DTPA uptake expressed as pulmonary/whole‐body (P/WB), extrapulmonary/whole‐body (EP/WB), and pulmonary/extrapulmonary (P/EP) deposition ratios after inhalation through 3 aerosol devices for 5 minutes. N = 10 dogs. Differences were not statistically significant. Error bars represent ranges. *Nose‐muzzle. ^99mTc‐DTPA, ^99mtechnetium‐diethylenetriamine‐pentaacetic acid

FIGURE 6

Mean nebulized ^99mTc‐DTPA uptake in the whole body, the sum of head region and stomach (extrapulmonary tissues) and the lung expressed in counts per minute after 1‐, 3‐, and 5‐minute nebulization. Used device: Aerochamber plus nose‐muzzle mask. N = 10 dogs. Error bars represent 95% confidence interval. P values related to 1‐minute nebulization are represented as asterisks (*P < .05; **P < .01; ***P < .001). There were no significant differences between 3‐ and 5‐minute nebulization. ^99mTc‐DTPA, ^99mtechnetium‐diethylenetriamine‐pentaacetic acid

FIGURE 7

Mean nebulized ^99mTc‐DTPA uptake expressed as pulmonary/whole‐body (P/WB) and extrapulmonary/whole‐body (EP/WB) deposition ratios after 1‐, 3‐, and 5‐minute nebulization. Used device: Aerochamber plus nose‐muzzle mask. N = 10 dogs. Error bars represent 95% confidence interval. The difference in the P/WB ratio was statistically significant (*) between 1‐ and 5‐minute nebulization (P = .03). ^99mTc‐DTPA, ^99mtechnetium‐diethylenetriamine‐pentaacetic acid