Emphysema is defined as the increase beyond normal in the size of airspaces distal to the terminal bronchiole. Such increases in airspace size are associated with a reduction in alveolar wall surface area <i>per</i> unit volume of lung tissue (AWUV). This study involved the development and assessment of the fast interval processor (FIP) as a new automated technique for measuring AWUV on histological sections of lung tissue. A minimum of 726 individual field AWUV measurements were made from each lung specimen, and frequency distributions of these AWUV values were compiled for each of the 165 specimens in the study. Various aspects of the frequency distributions were then used to establish the normal range of AWUV values with advancing age in non-smokers, and to assess the effects of age, sex and cigarette smoking on the amount and distribution of microscopic emphysema within the lung. Mean AWUV was found to decrease with advancing age in adult non-smokers, and this decrease was considered to be normal. A range of normal mean AWUV values was established for subjects between the ages of 21 and 93 years. No evidence was found to suggest that senile emphysema exists in non-smokers. Microscopically assessed emphysema (MAE) was defined as the condition where the mean AWUV measurement of a lung was below the lower limit of the normal range. Only 26% of the smokers studied had MAE as defined in this way, suggesting the existence of a suceptible sub-group of smokers. Neither the susceptibility to, nor the severity of, MAE were dose-related to tobacco consumption in the cigarette smokers studied. There were no sex differences in the incidence of MAE. MAE was found to be related to macroscopic panacinar emphysema, but was not related to macroscopic centriacinar emphysema. The 5th and 10th percentile values of the AWUV frequency distribution were found to be related to the presence of centriacinar emphysema. These results indicate that the early (microscopic) lesions in centriacinar emphysema are also focal in their distribution, and do not develop on a background of generalised MAE.
|University of Edinburgh
|Electronic Thesis or Dissertation
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