Thickness of the air-blood tissue barrier in infants

The harmonic mean barrier thickness of the alveolar air-blood tissue barrie r was measured in nine SIDS cases, six cases of unnatural death (three with asphyxiation, three without asphyxiation) and six cases showing interstiti al pneumonia (LP, three cases with lymphomonocyte infiltration of alveolar walls, three cases with peribronchiolar infiltration). Approximately 550-60 0 measurements were carried out in each case using micrographs with a final magnification of 11,000. The T-h values ranged between 0.37 mum and 0.39 m um in the SIDS group, in deaths due to asphyxiation and IP with a peribronc hiolar type of infiltration, were lowest in the unnatural deaths without as phyxiation (0.32 mum) and highest in cases showing TP with alveoloseptal in filtration (0.44 mum). The differences between the groups were significant (H-test, H-cor = 5.927). Compared to "normal" unnatural deaths (T-h = 0.32 mum), cases with interstitial cell infiltration of the alveolar septa showe d a nearly 40% increase of the barrier thickness which indicates a correspo nding decrease of the diffusion capacity. A decreased diffusion capacity ca n cause hypoxemia which could be an additional trigger mechanism in the dea th process.