| Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) is a kind of acute respiratory failure with high mortality, prone position ventilation ( PPV) can improve the oxygenation of ALI/ARDS. Rencently, PPV becomes a focus as a lung protective strategy and a method to elevate oxygenation function as a result of growing knowledge to ALI/ ARDS in which the lung isn't injured equally. So far, the mechanism for PPV improving oxygenation is not yet clear completely. We reproduced the rabbit's ALI model through oleic acid, aim to find the effect and possible mechanism of prone position and rotation treatment according to observe the model lung changes of oxygenation function, breathing mechanics, cytokine, lung pathology and lung CT, etc.Methods1. 1 Experimental groupsThe rabbits were divided into four groups, group 1:8 normal control rabbits; group 2: 8 experimental rabbits on supine position; group 3:8 experimental rabbits on prone position; group 4: 8 experimental rabbits rotating continuously.1.2 ALI model manufactureRabbits were anesthetised with an intraabdominal injection of 20% Ure-thane ( 5ml/kg ) ,then put the rabbits supine on the experimental table. The rabbits were tracheotomized and intubated with an 4mm interior diameter endo-tracheal tube , mechanical ventilation was initiated in A/C model with a VT of10ml/kg, a frequency of 30 breaths/ min , I: E =1:2. The external carotid artery was intubated to start arterial pressure and heart rate monitor; Swan-Ganz duct was inserted into the external jugular vein . Afterwards , oleic acid (0.08ml/kg ) was injected slowly into the external jugular vein of rabbits ,but rabbits in group 1 were injected with equal normal saline. Arterial blood gas a-nalysis was done every half an hour, in case PaO2/FiO2 < 300, ALI model was manufactured successfully.1.3 The body alterationAfter the AO model was manufactured successfully, rabbits in group 1 and group 2 still maintained lying supine for an hour ; rabbits in group 3 altered to lie on prone for an hour; rabbits in group 4 carried on the rotation continuously with 3 rings per minute on the specially made plat for an hour. Afterwards, carrying on various target examination.1.4 Target examination1.4.1 Hie examination of PaO2, PaCO2 and intrapulmonary shunt. Collecting arterial blood and doing gas analysis to achieve PaO2, PaCO2,SaO2, Hb. Through Swan-Ganz duct, collecting mixed venous blood to achieve PvO2, PvC02, SvO2. According to the formula, calculating intrapulmonary shunt.1.4.2 The examination of TNF-a and IL-6Collecting venous blood 4 ml , isolating serum to be conserved under -701. After all animal tests were finished, measuring serum concentration of TNF-a and IL- 6 by radio-immunity assay.1.4.3 Lung compliance measurement0.4 mg Pancuronium was injected to inhibit the breathing of rabbit , inserting esophageal ballon tube , then increasing VT to 15ml/kg, dropping breathing frequency to 10 breaths per minute, dropping the peak inspiratory flow to 5L/ min , maintaining I: E = 1:2 by means of regulating the inspiratory break time. In these conditions, Bear 1000t/es ventilator described out P-V curve automat-edly , and gave out the lung compliance, PIP,LIP automatedly on the basis of this curve.1.4.4 CT scanAfter an hour of ALI model was manufactured successfully, all rabbits were carried on helix CT scanning. Rabbits in group 2 were turned to prone from supine and keeping this position ten minutes, then accepted second CT scanning as CT group 5 ; Rabbits in group 3 were turned to supine from prone and keeping this position ten minutes, then accepted second CT scan as CT group 6. The CT scanning results were saved in hard disk, after that, CT section was analyzed as follows: choose the section at the top of diaphragma, dividing meanly the section into five strips from ventral to dorsal direction, marked as strip 1, strip 2, strip 3, strip 4, strip 5 on right lung and strip 6, strip 7, strip 8, strip 9, strip 10 on left lung, respectively; Fi...
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