Temperature distribution in the upper airway after inhalation injury.

OBJECTIVE: The aim of the study was to establish an animal model of laryngeal burn and to investigate the temperature distribution of heated air in the upper airway. METHODS: The animal model was established by inhalation of dry heated air at 80, 160 and 320 °C in 18 healthy, male, adult hybrid dogs. Time for inducing injury was set at 20 min. The distribution of temperatures after heated-air inhalation was examined at different locations including the epiglottis, laryngeal vestibule, vocal folds and trachea. RESULTS: The temperatures of the heated air decreased to 47.1, 118.4 and 193.8 °C at the laryngeal vestibule and to 39.3, 56.6 and 137.9 °C at the lower margin of vocal folds in the 80, 160 and 320 °C groups, respectively. CONCLUSION: Due to its special anatomy and functions, the larynx has different responses to dry heated air at different temperatures. The air temperature decreases markedly when the air arrives at the larynx. By contrast, the larynx has a low capacity for blocking high-temperature air and retaining heat. As a result, high-temperature air often causes more severe injury to the larynx and the lower airway.

[Quantification of type I and III collagen content in normal human skin in different age groups].

OBJECTIVE: To quantify the content of type I, III collagen and their ratio in normal human skin of different age, and to explore the regulation of changes. METHODS: The normal human skin specimens were obtained from 6 spontaneously aborted fetus and 56 burn patients of different ages, including infants (newborn -3 years), pre-school group ( > 3, < or =7 years), adolescent group ( >7, < or = 18 years), youth and middle age group ( > 18, < or = 50 years), and elderly group ( > 50 years), were studied. The total collagen content were determined by hydroxyproline method. The contents of type I, Ill collagen and their ratio were examined by immunohistochemistry. RESULTS: The total collagen content decreased along with increase in age, and it was highest in fetus [(543 +/- 13) microg/g]. The ratio between type I and Ill collagen increased along with increase in age. The content of type III collagen was highest in fetus [(278 +/- 7) microg/g], and it decreased along with increase in age. The content of type I collagen content was [(265 +/- 7) microg/g] in fetus, and it was increased slightly in infant and pre-school groups, then decreased along with advance in age. CONCLUSION: Decomposition of type III collagen in normal human skin may exceed its synthesis after birth immediately, leading to its reduction. Synthesis of type I collagen in normal human skin is dominant before 8 years old, and it shows an opposite tendency afterwards.