Microscopic demonstration of carbon deposits, observed coating the respiratory mucosa at autopsy, confirms smoke inhalation (Fig. 18; ref. 52). Microscopic examination of a burn can assess whether it occurred while the individual was alive. A few polymor-phonuclear leukocytes are seen migrating out of blood vessels at about 4 h (52,87). Leukocytic infiltration at the periphery of the burn is evident by 6 h. In most deaths at the scene, burns are postmortem, as the toxic effects of CO and smoke evolve rapidly. Certain histological findings can be caused by autolysis, e.g., mucosal detachment in upper airway
(see Subheading 4.1. and ref. 52). Elongation and palisading of epithelial nuclei in the respiratory tract is a postmortem heat effect (52). Hyperemia and edema of the airway mucosa are a vital but nonspecific reaction (52). The combination of pseudogoblet cells, increased mucus secretion, and vesicular detachment of respiratory epithelium has been considered indicative of antemortem heat effects, even in the absence of soot and increased COHb (52). Examination of lungs from deaths that occurred rapidly shows nonspecific findings (acute congestion, edema ). Although indicative of circulation following bony trauma, minor to moderate fat embolism has been seen in the lungs of some fire deaths in which blunt trauma has been excluded (see Chapter 8, Subheading 12.1. and refs. 42, 47, and 52).
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