Structural changes in the pulmonary vessels are usually first
evident in the muscular pulmonary arteries. Current methods for
quantitating the media, intima and artery size are inadequate
because they produce measurements that are affected by artery
collapse/constriction or the irregular distribution of intimal
abnormality within and between vessels, or they are unacceptably
tedious. New techniques were developed in this study to overcome
these problems; using a semi-automatic digitising system
measurements are produced, directly from histological sections, of
medial and intimal area, and artery size is defined as total length
of internal elastic lamina (IEL).Technique validation was carried out on thirteen subjects with
a variety of cardio-pulmonary disorders. At an appropriate
magnification reproducibility of the measurements is excellent.
Although only cross-sectional arteries with a well-defined IEL
('digitisable') may be measured these are representative of the
total population.The relationship between medial area and artery size is a
curved one, best linearised by taking the square root of medial
area. This latter relationship was used to investigate the effect
of different tissue preparation procedures on the measurements
obtained, specifically by comparing slopes of the regression lines.
Complete arterial distension by an injection medium caused the IEL
to stretch, x 1.5. However, neither the pressure/method used for lung inflation/fixation nor the tissue embedding medium affected the
above relationship. Tissue shrinkage was considerable with paraffin
embedding/sectioning and negligible with glycol methacrylate in
which more arteries were considered 'digitisable'.A new method for expressing intimal abnormality was devised,
the Intima Index, namely intimal area expressed as a proportion of
the area enclosed by the IEL in its theoretically unwrinkled state.
Values range from >0 to ^1 indicating minimal through to total lumen
occlusion. Subjects are compared by calculating mean Intima Indices
for arteries sub-divided by size.The medial and intimal areas of cross-sectional but
'undigitisable' arteries may be obtained by simply delineating the
boundaries of intima-media, and media-adventitia. The total length
of the IEL in such arteries is readily obtained by multiplying the
length of the intima-media boundary by a factor based on a by-eye
estimate of the degree of lamina 'crinkling'.The effects of age and smoking on muscular pulmonary arteries
were studied in thirty-two resection specimens and twenty-three
autopsy specimens. The amount of medial muscle was unaffected by
age, sex or smoking habit, and varied considerably between subjects.
In small arteries it correlated with absolute weight of right
ventricle.In the autopsy group the amount of intimal abnormality,
although very varied, increased with age in all sizes of artery but
was most prominent in the smaller ones; contrary to previous reports no lobar differences were evident. These trends were
strongest in smokers.The resection group was unsuitable for this study, the results
suggesting that superimposed on the effects of age and smoking there
is a degree of intimal fibrosis which results either directly or
indirectly from the presence of the bronchial carcinoma itself
