Biomedical Engineering Reference
In-Depth Information
In a morphometric analysis of pulmonary muscular arteries in these speci-
mens, Santos et al. (13) showed a significant enlargement of the intima,
compared with patients with mild COPD and control nonsmokers.
Conversely, medial thickness was slightly reduced in patients with severe
emphysema, when compared with patients with mild disease (13) (Fig. 1).
Contrasting with these findings, Turato et al. (14) did not find differ-
ences in intimal and medial thickness between patients with mild-to-
moderate COPD who underwent lung resection and patients with
severe emphysema who underwent LVRS.
C.
Smokers with Normal Lung Function
Structural changes in pulmonary arteries are not restricted to patients with
COPD. Morphometric studies performed by the authors (6) and others (15)
have shown that, compared with nonsmokers, pulmonary muscular arteries
of heavy smokers who have normal lung function show intimal thickening,
the magnitude of which does not differ significantly from that in patients with
mild COPD (6) (Fig. 1). These observations are in agreement with a former
post-mortem study conducted by Hale et al. (8) showing that cigarette smok-
ing was associated with morphologic changes in pulmonary muscular arteries
that evolve in parallel with small airway disease and emphysema.
D. Correlation with Lung Function and Pulmonary
Hemodynamics
In patients with mild-to-moderate COPD, the severity of pulmonary vascu-
lar remodeling is weakly correlated with the degree of airflow obstruction
and the magnitude of hypoxemia (4,6). Nevertheless, morphometric mea-
surements of pulmonary muscular arteries in patients with mild airflow
obstruction without hypoxemia may not differ from measurements in
patients with severe airflow obstruction with hypoxemia (5,13). Further-
more, in patients with severe disease, no correlation has been shown
between vascular changes and arterial blood gas measurements or the degree
of pulmonary hypertension (11,12).
The authors have shown that in patients with mild-to-moderate
COPD, the thickness of the intima was correlated with the impairment of
ventilation-perfusion distributions, and that intimal thickening was asso-
ciated with reduced efficiency of hypoxic vasoconstriction in maintaining
adequate ventilation-perfusion matching (4).
III. CHANGES IN VASCULAR CELLS
A.
Endothelial Cells
Endothelial cells play a pivotal role in regulating vascular homeostasis.
Changes in endothelial cell phenotype and function are thought to be at
