Publication: Pressure volume curve and alveolar recruitment/ de-recruitment. A morphometric model of the respiratory cycle
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Date
2002
Authors
Escolar Castellón, J.de D. ; Escolar, M.A. ; Guzmán, J. ; Roqués, M.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
H y p o t h e s i s : The changes in pulmonary
volume taking place during respiration are accompanied
by the opening and closing of the alveoli, with the
number of alveoli open, at the same transpulmonary
pressure (TPP) differing, depending on whether the lung
is insufflated or deflated.
Material and methods: Seventy 344 Fischer rats divided
into five groups. Group 1 lungs were fixed by instilling
10% formalin through the trachea to a pressure of 25 cm
H2O. The lungs of the next four groups were air- fi l l e d
and fixed via the pulmonary artery: group 2 lungs were
fixed in inflation at 10 cm H2O TPP; group 3 lungs were
fixed in inflation at 20 cm. H2O TPP; the lungs of groups
4 and 5 were fi xed in deflation and, therefore, were
inflated with air up to 27 cm. H2O to drop to 20 cm in
group 4 and to 10 cm in group 5. The lungs were
processed for light microscopy, carrying out a
morphometric study. The results were statistically
processed.
Results: The lungs insufflated with liquid fixative at 25
cm of TPP reached higher values in the va r i a b l e s
Pulmonary Volume, Internal Alveolar Surface (IAS) and
Number of Alveoli, being statistically signifi c a n t
(p<0.05) in comparison with the other four groups. In
the lungs fixed in deflation, the pulmonary volume, IAS
and number of alveoli were greater than in those fixed in
inflation. The lungs fixed to 20 cm in deflation displayed
s i g n i ficant statistical differences compared with those fi xed to 20 cm in inflation. The IAS and number of
a l veoli gave good rates in relation with the pulmonary
volume (r³ 0.65). Three variables were used to measure
the size of the alveoli, alveolar cord, alveolar surface and
Lm, but none showed significant modifications.
Conclusion: This study supports the hypothesis that
changes in lung volume are related to the
increase/decrease in the number of alveoli that are
open/closed and not to the modification in the size of the a l veoli. Alveolar recruitment is the microscopic
expression of pulmonary hysteresis, since the number of
alveoli open in deflation is greater than the number open
during inflation.
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