Objective   To investigate the different features of shock in both enclosed and outer space induced by blast injury combined with hemorrhage.    Methods   A total of 150 SD rats were divided randomly into 3 groups: enclosed space

outer space and control groups. Observation period lasted for 270 min after injury. Blast wave pressure was recorded and analyzed with data acquisition system. Mortality rate was calculated. Arte

rial blood gas detection

gross observation and pathological examinations were performed at 30

90

150

and 210 min after injury. Lung moisture content was also been counted [lung moisttue rate=(wet weight－dry weight)/wet weight×100%

]

.    Results   Compared with the outer group

enclosed group had 3-time longer time for shock wave pressare

high peak value of pressure

high reflected waves

and with the characteristics of complex wave. The mortality in enclosed group (53.8%) was higher than that of  in outer group (38.5%)

and the later one higher than control group (no death

P0.05). After the rats had haemorrhagic shock

the arterial blood pressure in enclosed space group was consistently below 40 mmHg

and it was upon 60 mmHg and then decreased rapidly in outer group after blast injury

with statistically significant difference at 30

150 and 210 min(P0.05). Lung edema in enclosed group was obvious than outer group at 270 min. Alveolar collapse

red cells accumulation

inflammatory cells infiltration and widen lung interval existed in lung pathology. Blood gas at different phases between enclosed and outer groups showed different alternation trends. Arterial oxygen saturation (SaO

2

)

haematocrit (Hct) and lactic acid (LAC) value were higher than those in enclosed group (P0.05).    Conclusion   There are different features of shock among enclosed and outer space induced by blast injury and hemorrhage and simple hemorrhage shock. The complex blast waves causes severe injury

early shock

higher mortality and worse compensatory capacity in enclosed rats.