Both the total and regional aerosol deposition were measured in six adult sheep before and after an induction of asymmetric airway obstructions, either by local instillation of carbachol solution (CS, 0.1%) distal to the right main bronchus or inhalation challenge of the right lung with carbachol aerosol (CA, 10 breaths). Total lung deposition was determined by monitoring inert monodisperse aerosols [1.0 μm mass median aerodynamic diam (MMAD)] breath-by-breath, at the mouth, by means of a laser aerosol photometer. Cumulative aerosol deposition over the first five breaths as a percent of the initial aerosol concentration (AD5) was used as a deposition index. Regional deposition pattern was determined by scintigraphic images of sulfur-colloid aerosol (1.5 μm MMAD) tagged with 99mTc. Radioactivity counts in the right (R) and left lung (L) were expressed as a percent of the whole lung count. Half-lung AD5 was then determined by multiplying AD5 by fractional radioaerosol depositions in R or L. Pulmonary airflow resistance (RL mean ± SE), as determined by an esophageal balloon technique, increased by 111 ± 28 and 250 ± 96% after CA and CS, respectively (P < 0.05). AD5 also increased in all the sheep tested by 29 ± 3 and 52 ± 8%, respectively, after CA and CS (P < 0.05). Radioaerosol deposition pattern was even at base line (R/L = 51:49) but shifted toward the unchallenged L after CS (R/L = 40:60). Deposition pattern after CA was variable: a shift toward L in three, no change in one, and a shift toward the R lung in two sheep. Half-lung AD5 increased in both lungs: 18 ± 6 and 23 ± 5% in R after CS and CA and 79 ± 10 and 36 ± 9% in L after CS and CA, respectively (P < 0.05). Results indicate that total lung deposition increased with asymmetric airways obstruction regardless of deposition distribution and that deposition enhancements occur more in the less obstructed lungs receiving greater airflows.
- Carbachol aerosol
- Radioaerosol imaging
- Regional deposition pattern
ASJC Scopus subject areas
- Orthopedics and Sports Medicine
- Physical Therapy, Sports Therapy and Rehabilitation