Journal of Applied Physiology, Vol 69, Issue 6 2104-2112, Copyright © 1990 by American Physiological Society
Persistence of enhanced aerosol deposition in the lung after recovery from carbachol-induced airway obstruction
C. S. Kim, L. Garcia, M. A. Eldridge and A. Wanner
Pulmonary Division, University of Miami School of Medicine, Mount Sinai Medical Center, Miami Beach, Florida 33140.
Time course recovery from induced airway obstruction by carbachol infusion
(CI; 0.2 microgram.kg-1.min-1 for 40 min), carbachol aerosol (CA; 10
breaths of 2% solution), and histamine aerosol (HA; 25-50 breaths of 5%
solution) challenge was investigated in conscious sheep (n = 6 each). Total
lung aerosol deposition and airway caliber as assessed by pulmonary airflow
resistance (RL) were measured every 20-30 min up to 4 h after the
challenges. Aerosol deposition was measured by monitoring aerosol
concentration continuously with a laser aerosol photometer while the sheep
rebreathed 1.0-micron-diam inert oil droplets delivered by a 0.25-liter
bag-in-box system driven by a respiratory pump at a breathing frequency of
30 breaths/min. Total accumulated deposition at the fifth breath (AD5) as
percentage of the initial aerosol concentration was determined and used as
an aerosol deposition index. Percent changes in AD5 from baseline were
compared with corresponding changes in RL. Both RL and AD5 increased after
Cl, CA, and HA: 192-477% for RL and 23-44% for AD5 (P less than 0.05). Mean
RL return to baseline values 1 h after CI and HA and 2 h after CA. Mean AD5
returned to baseline at 1 h post-HA. In contrast, mean AD5 remained
elevated for 2-4 h after CI and CA (P less than 0.05), and the increased
AD5 could not be reversed by a bronchodilator aerosol. The persistence of
enhanced aerosol deposition long after the return of RL to baseline
suggests that complete recovery of airway conditions after CI and CA takes
much longer than predicted by RL.(ABSTRACT TRUNCATED AT 250 WORDS)
