Mucosal fluid evaporation is not the method of heat dissipation from fourth-degree laryngopharyngeal burns.

This study was designed to explore whether mucosal fluid evaporation represents a method of heat dissipation from thermal air inhalation injury and to assess laryngopharyngeal tissue damage according to heat quantity changes of dry air and vapour. Fifteen adult male beagles were divided into five groups to inhale heated air or vapour for 10 min as follows: control group (ordinary air), group I (91-110 °C heated air), group II (148-175 °C heated air), group III (209-227 °C heated air), and group IV (96 °C saturated vapour). The heat quantity changes of the dry air and vapour were calculated via thermodynamic formulas. The macroscopic and histological features of the laryngopharynxes were examined and assessed by various tissue damage grading systems. Group IV exhibited the most serious laryngopharyngeal damage, including cilia exfoliation, submucosal thrombosis, glandular atrophy, and chondrocyte degeneration, which is indicative of fourth-degree injury. The quality, heat quantity, and proportional reduction of heat quantity of vapour in group IV were all higher than those in the other groups. Furthermore, we found that mucosal fluid evaporation is not the method of heat dissipation from thermal air inhalation injury used by the airways. Laryngopharyngeal tissue damage depends chiefly on the heat quantity of vapour in the air.

Circulational heat dissipation of upper airway: Canine model of inhalational thermal injury.

BACKGROUND: The upper airway has powerful heat-absorbing ability, in which the blood circulation may play an important role. OBJECTIVE: This study aimed to explore the circulational heat-dissipating ability, and to investigate the contribution of blood circulation to the heat-absorbing ability of upper airway. METHODS: 18 adult, male Beagle dogs were divided into three groups to inhale thermal dry air of 70-80°C, 150-160°C or 310-320°C for 20min. Blood temperatures and blood flow rates of bilateral common jugular veins (CJVs) were measured. Dogs' breathing rates and air temperatures in middle trachea were also measured. According to the formula "Q=c·m·ΔT", the heat dissipated by blood (Q-blood) and the heat release by air (Q-air) were calculated out. The contribution of circulational heat dissipation to the heat-absorbing ability of upper airway was defined as "C-blood". RESULTS: The blood temperature rise of CJV was 2.24±0.60°C. The blood flow rate of CJV was 44.5±5.9ml/min. The air temperature in middle trachea was 63.5±18.9°C. The mean breathing rate was 51.8±7.5/min. The calculated "Q-blood" and "Q-air" were 13197.3±4408.6J and 33540.2±24578.7J, and the "C-blood" was 55.2±25.0% (21.7-88.8%). CONCLUSION: Circulational heat dissipation plays an important role in the heat-absorbing process of upper airway when inhaled air is less than 160°C. However, for air higher than 160°C, some other mechanism might be dominant in the upper airway's heat-absorbing ability.

[Analysis of 59 cases of frostbite in plain region].

OBJECTIVE: To retrospectively survey frostbite in patients living in plain regions, and to analyze the features of frostbite and the results after hospitalization. METHODS: Fifty-nine patients with frostbite, aged from 15 to 85 years admitted in Beijing Jishuitan Hospital from 1992 to 2007, were enrolled in this study. Occupation, cause of the injury, initial visit time, position and degree of depth (assessed according to the standard of burn injury) of frostbite, and amputation rate of patients were recorded and analyzed. RESULTS: Most patients of the 59 cases were workers or unemployed, the main reasons of injury were prolonged contact with material in a low temperature, with impaired consciousness, and having an out-door activity. The average first visit time was 11 days after the exposure. Frostbite was superficial 2(nd) to deep 2(nd) degree in 12 patients, while 47 patients were found to have 3(rd) to 4(th) degree injury. Limbs, or fingers and toes were amputated from 40 patients. The differences between patients visited within 3 days after frostbite and patients visited later than 3 days in respect of degree of depth of frostbite and amputation rate were statistically significant (P < 0.05). There was no significant difference in amputation rates in different body parts of frostbite (P > 0.05). CONCLUSIONS: Patients in plain regions mainly suffer frostbite at the distal portions of the extremities. They should visit hospital early after injury so that the degree of frostbite can be alleviated and rate of amputation can be lowered.