US EPA

1976587 

Journal Article 

Compliance of peripheral airways deduced from morphometry 

Okazawa, M; Paré, PD; Lambert, RK 

2000 

Yes 

Journal of Applied Physiology (1985)
ISSN: 8750-7587
EISSN: 1522-1601 

89 

6 

2373-2381 

English 

11090592 

10.1152/jappl.2000.89.6.2373 

WOS:000165736400038 

http://://WOS:000165736400038
Exit
 

Insights into airway mechanics were sought by applying morphometric techniques to rabbit lungs fixed at several lung recoil pressures. Rabbits were treated with either nebulized carbachol followed by iv administration of carbachol or with saline solution (sham). The lungs were held at one of six values of positive end-expiratory pressure (PEEP; 10, 7, 4, 2, 0, and -4 cmH(2)O) while the animal was killed and formalin was circulated through the lungs. The lungs were removed and left in a bath of formalin for 24 h. Standard airway morphometric measurements were made on membranous bronchiole slices taken from representative blocks of tissue. Reductions in PEEP produced the expected reductions in lumen area in the carbachol-treated airways but not in the sham-treated airways for PEEP > 2 cmH(2)O. Sham-treated airways remained more open than expected until they collapsed into an oval shape at PEEPs between 4 and 2 cmH(2)O. The carbachol-treated airways exhibited this behavior at PEEP = -4 cmH(2)O. The smallest airways, which had relatively thicker walls, collapsed less than larger airways. We postulate that this behavior implies that peribronchial stress is greater than lumen pressure on collapse into the oval shape. Resistance to buckling increases with the thickness-to-radius ratio of the airway wall, which explains why the smallest airways are the most open. The development of epithelial folds appeared to follow the theoretical prediction of a previous study (Lambert RK, Codd SL, Alley MR, and Pack RJ. J Appl Physiol 77: 1206-1216, 1994). 

rabbit; airway mechanics; carbachol; elastic buckling