ABSTRACr Standard morphometric methods were applied to the lungs of 36 boys and 20 girls aged from 6 weeks to 14 years, dying as a result of trauma or after short illnesses. Individual lung units, alveolar dimensions, and number of alveoli per unit area and volume did not differ between boys and girls, but boys had bigger lungs than girls for the same stature. This resulted in a larger total number of alveoli and a larger aveolar surface area in boys than in girls for a given age and stature. There may be more respiratory bronchioles in boys than girls. There was rapid alveolar multiplication during the first two years of life and alveolar dimensions and number of alveoli-per unit area and volume did not change much during this period. There was little or no increase in the total number of alveoli after the age of 2 years but the data are hard to interpret. There is a wide scatter of the total number of alveoli in the growing lung, in keeping with the observation that the total number of alveoli is very variable in adults. Prediction data are given for the various morphometric variables studied.In 1962 Dunnill' applied the morphometric technique developed by Weibel2 to postnatal lung development in 10 children of unstated sex between birth and 8 years. He found that there were 20 million alveoli at birth and that alveolar multiplication was rapid in the first few years of life. He reasoned, from the then available data in adults, that alveolar multiplication slowed after the age of 4 years and stopped at 8 years He found a very precise linear relationship between alveolar surface area and body surface area and a correlation coefficient of +0-999 can be calculated from his data. Davies and Reid,3 although more interested in the growth of the pulmonary arteries, studied alveolar growth in five children between birth and 11 years (three boys and two children of unstated sex) and found similar results for total alveolar number, their figures being about 10% higher than Dunnill's. Thurlbeck and Angus4 studied lungs from 14 subjects of unstated sex from birth to 19 years and likewise found a rapid increase in total number of alveoli in the first four years of life. Their report, however, differed from the two previous ones in that their data showed a much greater scatter of total alveolar number. Dunnill' and Davies and Reid3 suggested that alveolar dimensions changed little in the first few years of life. Dunnill's data, however, show an increase in alveolar diameter that can be calculated to be significant. Reid and Davies showed a fall in alveoli per unit volume in their cases; Dunnill by contrast found no change between birth and the age of 4. In three of the cases of Davies and Reid death was from trauma; one child died after surgery; and one was stillborn. The age of the last is uncertain but the lung volume was about one-quarter that of a full-term infant.' The cases in the other two series were derived from hospital necropsies on children dying from non-respiratory causes.Thus the number of cases studied so fa...
We studied the lungs of seven patients of various ages who had Down's syndrome, to determine whether they had abnormalities in pulmonary development. Six of the seven had hypoplastic lungs. Five had congenital heart disease, but pulmonary hypoplasia was of equal severity, irrespective of the presence or absence or the type of congenital heart disease. Three other patients with congenital heart disease but without Down's syndrome had lungs that were equally diminished in volume. However, these lungs lacked the structural abnormalities seen in Down's syndrome, which consisted of a diminished number of alveoli in relation to acini and enlarged alveoli and alveolar ducts. The patients with Down's syndrome also had a smaller total number of alveoli and a smaller alveolar surface area. We speculate that the smaller alveolar surface area is accompanied by loss of capillary surface area, which is responsible for the aggravation of pulmonary hypertension in Down's syndrome.
ABSTRACr The radial alveolar count method of Emery and Mithal has been re-evaluated on 76 normal postnatal lungs. Results of reproducibility assessments suggest that each observer should establish normal control values when beginning with the method, and should subsequently use control cases to maintain strict reproducibility. The use of 10 fields per case was found to be inadequate to obtain satisfactory reproducibility, even for a single observer. Prior inflation of the lungs significantly increased the radial counts, and this factor may help to explain the large discrepancy between the results of this study and that of Emery and Mithal. The radial counts correlated well with the chronological age of the child (r = +0*76; p < 0.001).Alveolarisation of the acinus occurs primarily between birth and 2 years; significant but slower growth is seen up to 8 years, after which the results plateau, suggesting that alveolarisation is complete. The radial count method appears to provide a relatively simple and reasonably satisfactory assessment of alveolar development, as originally proposed by Emery and Mithal.There is a wide variation in estimations by different observers of the number of alveoli in the human lung at a particular age and of the time at which alveolar multiplication ceases. These discrepancies have been attributed to several causes'-different methods of preparation of the lungs for analysis; variation in results between different observers when the same sections are examined; difficulty in recognition of alveoli; and the small number of cases from which current data have been derived. Additional theoretical limitations are imposed by the alveolar shape constant (a3) that study were made from a respiratory bronchiole to the edge of the acinus. A respiratory bronchiole was defined as a bronchiole lined by epithelium in one part of the wall. From the centre of such a bronchiole a perpendicular was dropped to the edge of the acinus (connective tissue septum or pleura), and the number of alveoli cut by this line was then counted. Ten such counts were made from each of 309 cases and the mean for each case was estimated. Results were expressed as average figures in different age groups, and an increase in the radial alveolar count throughout the whole of childhood was documented. By the use of this method of choosing bronchioles adequate reproducibility of results was said to have been achieved.Although the information derived by this method differs from (and is less than) that obtained by conventional alveolar counting, the technique has obvious merits. Large numbers of cases may be rapidly examined. It is claimed that the method overcomes
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