| Objective To explore the time and development of hypoxemia of rabbits with scald injury in hot and humid environment and analyse the cause and pathogenesis of hypoxemia. The study is to offer theoretical bases to establish the assessment criteria of hypoxemia on scald injury in the south battlefields and regions and lay experiments foundation of monitoring and treatment of respiratory function of scald patients in south battlefields and regions.Methods 24 New Zealand male rabbits were divided into 4 groups randomly with equal numbers. Rabbits observed without scald in normal environment was designated as group cwwt, those with scald in normal environment as group cwts, those without scald in hot and humid environment as group gwwt and those with scald in hot and humid environment as group gwts. The dorsal skin of rabbits with scald were immersed in 95 ℃ water for 30s. This procedure produced a full thickness burn of 30% total body surface area (TBSA). The hot and humid environment condition was Tdb38℃ and relative humidity 65%?%; The normal environment was Tdb2?1 ℃ and relative humidity 55% ?5%. The exposure time of each group was 120 minutes. During the test, the basic vital body and blood-gas indexes were taken once per 40 minutes. The rabbits of each group were skilled at 120min and rem em*I cm lung to have histological assessment.Results (1) Changes in vital signs : Tr , RF as well as HR of the rabbits in group gwts and group gwwt increased gradually during the experiment(P<.05), MAP decreased gradually (P<.05); HR of the rabbits in group cwts increased gradually after scald (P<.05), MAP decreased gradually(P<0.05), but Tr and RF had no changes during the experiment (P>.05); The indexes of vital signs of rabbits in group cwwt had no changes during the-4-experiment (P>0.05). Based on the comparison of inter-group at the same time, the width of the change of each index is that group gwts>group gwwt>group cwts>group cwwt (P<.05).(2) Changes of blood gas: PaO2 of the rabbits in group gwts decreased in the SOmin period after scald (P<.05), SaO2 decreased in the 120min period (P<.05), PaCO2 decreased gradually and PA-aO2 increased gradually (P<.05). PaO2 and SaO2 of the rabbits in groups gwwt and cwts didn't change during the experiment (P>0.05), but PaCO2 decreased gradually and PA-aO2 increased gradually (P<.05). The indexes of blood gas of rabbits in group cwwt didn't change during the experiment (P>0.05). Based on the comparison of inter-group at the same time, the width of the change of each index is that group gwts>group gwwt>group cwts>group cwwt (P<.05).(3) Histological changes of lung: Compared with the histological change in group cwwt, histological manifestation of damage to the lung occurred in group cwts gwwt gwts were characterized by the widening of alveolar wall with inflammatory cellular and red blood cell infiltration, the group gwts was more serious than the other groups.Conclusion (1) The changes in vital signs of the rabbits with scald in hot and humid environment were more serious than that of each single factor. The changes were in accord with the development of hypoxemia; (2) The rabbits in the group gwts were injured mainly by hot and humid environment and scald with earlier hypoxemia, Obvious hypoxemia were observed at 80 minute after scald, at that tune the slight decrease of PaO2 may affect obviously SaO2. Hypoxemia after scald in hot and humid environment develops faster than that of scald in normal environment, it develops to type I respiratory failure at 120 minute after scald; (3) Hypoxemia after scald in hot and humid environment was caused by oxygenation failure resulting with VA/Q imbalance and disfunction of-5-diffusion capacity, with compensatory increasing of ventilatory function; (4) Histological damage to the lung after burn in hot and humid environment is more serious than that of burn in normal environment, it is characterized by the widening of alveolar wall with inflammatory cellular and red blood cell... |
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