| Explosive weapons, with characteristics such as wide antipersonnel area, multi-factor injuries and big casualties, are widely used in modern wars. Explosive weapons mainly cause injuries through the high-energy explosive fragment and shock wave produced at the moment of explosion. The injury caused by explosive weapons are usually serious, complicated and hige early mortality. Therefore, the injury research of explosive weapons is catched more and more attention.Some domestic and overseas scholars have made short-distance animal injury experiments by using the compound fragment of shock wave or the small explosion source, all of them were carried out in open air, and mainly compound injury. However, in the building and confined space, such as military fortifications, tunnels, mines and vehicles, the explosion injury on people is mainly caused by the shock wave. The explosive produces enormous energy in explosion process makes the air expand and forms spherical high pressure. The pressure is much higher than normal air pressure, which is called"overpressure". When the shock wave interacts with the objects it encounters, part of the wave are reflected. In the mutual overlap region of the reflected wave and the incoming wave, the pressure in some part can be as several times high as the overpressure, so the mortality of explosion is higher and the destructiveness is bigger. Cooper and other researchers indicated that the shock wave is transmitted in the body in the form of stress wave, shock wave and shear wave and damages internal organs after affecting the body. The stress wave is a kind of vertical pressure wave, with higher energy, its transmitting speed is similar to the speed of sound. Stress wave will produces high pressure while transmitting between organs. When traveling to the interface of two regions with different acoustic impedance such as the lung, different pressure is produced on two sides of the interface, and then result in organ injury. The noise in indoor explosion can makes echo in a confined space, which makes the sound far higher than that in outdoor, and leads to high stress reaction on organisms, so that makes the pathological change more complicated. In addition, indoor explosion consumes a large amount of oxygen, produces thick explosion smoke and a large quantity of gases such as carbon monoxide, which aggravates the hypoxia of the injured biology. These factors indicate that there is a great difference between the indoor blast injure and outdoor explosion injure.Objectives: To establish the indoor explosion conditions, and explore the effect of the shock wave generated by the indoor explosion on physiological effects in dogs and the changes law of early hemorrheological guidelines.Methods: 22 healthy dogs, male or female, weight is 12.71±0.81 kg for each one. According to the quality of explosives and the distance between the explosive source and the dogs, randomly divided the dogs into three injure groups (6 dogs in group A: 40g/1.0m; 6 dogs in groupB: 80g/1.0m; 5 dogs in group C: 80g/0.8m) and 5 dogs in a control group without injury. After anesthesia dogs were fixed on vulnerating-bench. The distance between the appendix ensiformis of the dog and the ground was 1m. The injury of dogs were generated in detonation tower and VXI-1115 Dynamic Tester(sampling frequency of 2 Mb/s) and PCB137 free field pressure sensor were used to collect the pressure data produced by explosion in detonation tower. The breathing, heart rate, blood pressure, arterial blood gas, hemorrheological changes indicators and changes of heart pathology were observed at four time points of 1 h, 3h, 5h, and 12 h after injury.Results After injury, five dogs were dead instantly. Non-dead injured dogs showed a brief apnea, then a fast shallow breathing. 30-60 minutes later, the breathing became slow and deep (3-8 times/min) which was significantly lower than that of control. The heart rates of dogs after injury were significantly lower than that of the control group. 40 minutes later, the heart rate dropped to the lowest point (54.2 times / min), and then gradual increased, which reached the peak in 2 to 3 hours, and then decreased, which were significantly different to the control group. ST segment changes of ECG were observed in all the injured dogs. After injury, the average blood pressure of dogs was 56.4 mmHg, which then gradually increased and reached the peak in 2 hours. The average contractive pressure was 85.25 mmHg, it was still lower than that of control group (P <0.05). The result of arterial blood gas of dogs after injury indicated that, the greater of energy of explosion shock wave was, the more serious injury of dogs was. It showed that CO2 accumulation, and the decreasing of partial pressure of oxygen and SaO2 and pH. The results of myocardial pathological biopsy showed that myocardial injury also increased with the increase of overpressure, the heart wall hemorrhage, myocardial fiber necrosis or fracture, erythrocyte accumulation in muscle fibers, diffuse congestion between the papillary muscles and chorda tendineae, a small number of infiltration of inflammatory cells in mesenchymal, thick stain of myocardial cells, and the edema change of surrounding. In the hemorrheology, whole blood viscosity, plasma viscosity, erythrocyte aggregation index, whole blood reduced viscosity, RBC rigidity index were significantly higher than that in the control group, and erythrocyte rigidity index were lower than that of control group.Conclusion Our study showed that indoor explosion had a significant impact on the body physiology and hemorrheology in a short period of time after injury. The decreases of respiratory rate, heart rate and blood pressure of dogs were related to the vagus nerve of animals, and also related to myocardial cells damaged. The lower blood volume may be caused by pulmonary hemorrhage. The hemorrheological changes was closely related to the physical, chemical factors such as wide vascular endothelial cell injury, stress inflammatory mediated cytoskeleton contraction, as well as the lower of blood pH value. |
