| Background:The impact injury is ordinary accident in peacetime,especially in traffic accidents.Contralateral pulmonary injury can be caused by direct trauma following unilateral blunt chest trauma:the contre-coup effect or can be related secondary lung injury by systemic and local inflammatory reactions ,but relative literatures have been little reported.Objectives:⑴ To study the mechanisms of primary and secondary injuries in contralateral lung after unilateral chest impact,and to find out the role of secondary inflammatory reactions in the occurrence of acute lung injury(ALI) and acute respiratory distress syndrome(ARDS) following blunt chest trauma.⑵ To explore the diagnostic value of single photon emission computerized tomography(SPECT),thoracic computed tomography(TCT),chest X-ray(CXR) on experimental pulmonary contusion,and to understand the injury rule in both lungs after unilateral chest impact.Methods:⑴ By randomized and controlled animal study,forty-eight New Zealand white rabbits were divided into matched control and different time groups after trauma(at 1,6,and 24hrs,respectively).The animal model of unilateral chest impact injury were imitated by BIM-Ⅱ biological impact machine.To analyse the alterations of biological markers(lung wet/dry weight ratio,count of polymorphonuclear neutrophil(PMN) and content of protein in bronchoalveolar lavage fluid(BALF),and pulmonary microvessel permeability) in bilateral lungs,and to measure the expressions of TNF-α and G-CSF mRNA in both lungs with reverse transcription polymerase chain reaction( RT-PCR) technique, and to determine the changes of MIP-2 and LTB4 in plasma,both BALF and lung homogenates with enzyme-linked immunoadsordent assay (ELISA) ,and to evaluate the injury score of important organs after unilateral chest impact.⑵ Using prospective method,to evaluate radiological changes of TCT and CXR on pulmonary contusion,and to draw the curve of bilateral lungs along with time after trauma by region of interesting (ROI) technique in SPECT.Results:⑴ The significant changes of pulmonary biological markers appeared in both lungs at different time after trauma (P﹤0.05～0.01).Increasing of TNF-αand G-CSF mRNA expressed in bilateral lungs,and the significant changes of MIP-2 and LTB4concentration in plasma,both BALF and lung homogenates appeared at different time points following unilateral blunt chest trauma.The result of important organs injury score manifested:the injury score between right lung and chest wall existed significant positive correlation,r=0.477,P＜0.01.The injury score of both lungs correlated fairly with each other,r=0.436,P＜0.05,but between left lung and chest wall there was no significant correlation on the injury score ,r=0.250,P＞0.05. ⑵ At 1,6,and 24 hours after trauma,the pulmonary contusion sensibitity of CXR were 33.33%(3/9),55.56%(5/9),and 75.00%(6/8),respectively.Two of 9(22.22%) contusions escaped detection on conventional radiographs. Two of 2(100%) contusions were visible by TCT at one hour after trauma, and the lesions size of CT were identical with practical pulmonary contusion volume. Respectively, the curves of ROI average count ratio between bilateral lungs with heart were heighten along with time,the peak at six hour after trauma.There were significant differences in bilateral lungs at different time after trauma(P﹤0.01).Conclusions:⑴ Primary and secondary injuries of contralateral lung can be led ,and poly-endogenous inflammatory media were involved in secondary injury of contralateral lung following unilateral blunt chest trauma.The secondary inflammatory reactions may be important mechanisms of occurrence and development in ALI and ARDS after lung contusion.⑵ The injury score between contralateral lung and chest wall there was no significant correlation,and the result demonstrated existing different mechanisms of trauma on contralateral pulmonary primary injury.⑶ The diagnostic sensibitity of pulmonary contusion TCT is superior than conventional radiograph,but TCT is inferior than SPECT on exudation...
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