Morphological hysteresis of the small airways
J.D. Escolar1, M.A. Escolar1, J. Guzmán2 and M. Roqués3
1Morphological Science Department, Faculty of Medicine, University
of Zaragoza, Spain, 2Anatomy Institute of Biomedical Science,
Autonomous University of Ciudad Juárez, Mexico and 3Pediatrics
Department, La Fe Hospital, Valencia Spain
Offprint requests to: Juan
de Dios Escolar, Department of Morphological Science, Faculty
of Medicine, University of Zaragoza, Domingo Miral s/n 50009,
Zaragoza, Spain. Fax: +34 976761754. e-mail: jescolar@posta.unizar.es
Summary. The resistance to airflow that develops in
most obstructive processes takes place in the small airways. The
aim of the present paper is to describe bronchial hysteresis morphometrically
in a respiratory cycle model. As a working hypothesis, it is proposed
that the changes that take place in the respiratory tract during
the respiratory cycle are related to the bronchial size.
Specimen rat lungs were organized into five groups: In the first
group, the lungs were filled with a liquid fixative to 25 cm of
H2O transpulmonary pressure. The following four groups were inflated
with air and fixed through the pulmonary artery. Groups 2 and
3 were fixed at 10 and 20 cm transpulmonary pressure in inflation.
The last two groups were fixed in deflation and, for this purpose,
the transpulmonary pressure was increased to 27 cm and decreased
to 20 and 10 cm, respectively. The lungs were processed for morphometrical
study and the following variables were quantified: pulmonary volume,
internal area, internal perimeter, wall area, internal area radius
and bronchial wall radius. The diameter of the airways studied
varied between 84.06 µm and 526.4 µm. The results
were classified into three subgroups consisting of small, medium-sized
and large bronchi.
With a single exception - the internal area in the medium-sized
bronchi inflated to 20 cm - all the results obtained in deflation
were higher than those obtained in inflation. The internal area
increased or decreased significantly upon raising or lowering
the transpulmonary pressure respectively, in the small and medium-sized
bronchi. The wall area in the large bronchi showed significant
differences between inflation and deflation at 10 and 20 cm transpulmonary
pressure. The wall area was modified significantly in the lungs
fixed at 20 cm in the small bronchi and at 10 cm in medium-sized
bronchi. The bronchial wall radius was significantly greater in
the large bronchi and smaller in the small bronchi.
The lumen of the medium-sized and small bronchi increases in inspiration
and decreases in expiration. The wall thickness displayed differences
between inflation and deflation. The most marked hysteresis was
presented by the bronchial wall in the large bronchi. Our results
suggest that the behavior of the bronchi varies according to their
size. Histol. Histopathol. 18 19-26 (2003)
Key words: Bronchus, Hysteresis, Rat, Morphometry
DOI: 10.14670/HH-18.19