Experimental Study On Pulmonary Function Induced By CO₂ Pneumoperitoneum In The Rabbit Models With Chronic Pulmonary Function Failure

Objective: Laparoscopic technology has been widely used in most of clinical practice. In the most cases, the laparoscopic procedures are carried out under CO₂ artificial pneumoperitoneum. A lot of basic experiments and clinical trials have found that the pneumoperitoneum has potentially hazardous side effects. Some studies indicated that hepatic, renal and lung ischemia developed during pneumoperitoneum, and that their functions were impaired after pneumoperitoneum. But most of researches were concentrated on organs of normal body. The purpose of this study was initiated to investigate the changes and possible mechanisms of pulmonary function induced by CO₂ pneumoperitoneum in the rabbits with chronic respiratory disease.Methods: The rabbit models with chronic pulmonary function failure were established by intravenous injection 8% papain into auricle vena and inhalation 5% papain of ultrasonic atomization. After a period of 9 weeks stabilization of animal models, the arterial blood sample were collected from arteria femoralis to analyze blood gas (pH, PaCO₂, PaO₂). Pulmonary function was checked and an X-RAY film of chest was taken. 45 rabbits with abnormal level of these parameters and x-ray abnormal appearance were randomly divided into 9 groups. The CO₂ pneumoperitoneum was established through Veress needle with an automatic insufflator. The pressure was maintained 10mmHg(1.33kPa) in 4 groups, 15mmHg(1.97kPa) in the other 4 groups (one group of gasless serve as a sham included) respectively for 2 hours. Animals in each group were collected and blood gas was analyzed from the arterial blood samples by arteria femoralis at instant, 1h, 2h after the start of pneumoperitoneum and lh, 2h, 3h, 4h, 5h, 6h, 18h after the end of pneumoperitoneum. And the pulmonary function was checked by impulse oscllometry at instant, 2h, 4h, 6h and 18h after the end of pneumoperitoneum. The animals were killed and lung tissue was collected at instant, 2h, 6h and 18h after the end of pneumoperitoneum. 500mg tissue of lung wasmade into homogenate. Xanthine-oxidatase, Barbiturate hyposulfite, Colorimetry, and prismatic-ultraviolet light methods were used to measure superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), Myeloperoxidase (MPO), catalase (CAT), maleic dialdehyde (MDA) and glutathione (GSH) in lung homogenate, respectively. The rest of lung tissue was fixed in 10% phosphate-buffered formalin, dehydrated, embedded in pafraffin, sectioned and stained with hematoxylin and eosin (H-E). Histological changes of lung tissues were examined under light microscopy.Results: 1. The levels of pH, PaCCh were elevated and the level of PaO2 was reduced at the pressure of CO2 pneumoperitoneum in this experiment. The variation of these parameters was the most significant at 2h after the end of pneumoperitoneum. And these variations recovered in some degree at 18h after the end of pneumoperitoneum, but the level of these parameters was lower than that of before pneumoperitoneum. These variations were more significant in 15mmHg (1.97kPa) groups than lOmmHg (1.33kPa) groups. 2. Reduced SOD, CAT, GSH-PX AND GSH was observed in the lung tissue after pneumoperitoneum, and the level of these parameters were the lowest at 2h after the end of pneumoperitoneum. And these variations had some recovery at 18h after the end of pneumoperitoneum, but the level of these parameters was lower than that of before pneumoperitoneum. The variations of MDA and MPO are quite opposite to other parameters. All above variations were more significant in 15mmHg (1.97Kp) groups than lOmmHg (1.33kPa) groups. 3. Increased airway resistance was observed after the end of pneumoperitoneu by impulse oscllometry. These variations were more significant in 15mmHg (1.97Kp) groups than lOmmHg (1.33kPa) groups 4. Pathological examination of lung revealed characteristics of choric pulmonary function failure on animal models. 5. The X-ray of lung appearance corresponded with chronic obstructive pulmonary disease.Conclusion: These effects of CO2 pneumoperitoneum are only transient and reversible on normal body in clinical practice. But they were remained on pulmonary function of rabbit with chronic obstructive pulmonary disease in our study. Their behaviors included the hemodynamic changes and respiratory resistance increase. Furthermore, with the rise of CO2 pneumoperitoneum pressure, the variation was more severe. It was possible that a great shock in the pulmonary function occurred for body with chronic pulmonary function failure.We may draw a conclusion that degressive pulmonary function and hypoxia were observed in rabbits with chronic pulmonary function failure after established CO2 pneumopentoneum. Three aspects were the points. 1. Blood gas: The levels of pH, PaCO2 were elevated and the levels of PaO2 were reduced. 2. Breathing physiology: These airway resistances that reveal breathing physiology showed elevation such as total airway resistance, center resistance and total air passage resistance. 3. Oxidative stress reaction: The activities of antioxidant enzymes including SOD, CAT, GSH-PX and GSH were reduced in the lung tissue. While the activities of MDA and MPO, which reflected oxidative impair in the lung tissue, were elevated. 4. Pathological examination: The lesion of pulmonary tissue due to CO2 pneumoperitoneum is obvious under light microscopy. These variations were more significant in 15mmHg (1.97Kp) pressure groups than lOmmHg (1.33Kp) pressure groups.The purpose of this study was initiated to investigate the changes and possible mechanisms of pulmonary function induced by CO2 pneumoperitoneum in the rabbits with chronic pulmonary function failure. In this study, we wondered how to select appropriate measures for reducing lesion induced by CO2 pneumoperitoneum. And our study gave some safe and feasible rationales for patients with chronic pulmonary function failure, who would have to face a laparoscopic operation under CO2 pneumoperitoneum. For patients with chronic pulmonary function failure, the methods of therapy depended on their overall conditions. A thorough examination of lung and heart and drugs for improving pulmonary and cardiovascular function were necessary before operation. In operation, we should reduce pressure of CO2 pneumoperitoneum and operational time as long as possible in the condition of not disturbing operation. And the hemodynamic changes of patients should be closely monitored at the early stage of establishment CO2 pneumoperitoneum. While preventing hypercapnia and acidosis, we should improve blood supply of lung and decrease oxidative free radicals in body. In the end, we would reduce lesions and risks induced by CO2 pneumoperitoneum. So applications of laparoscopic technology would be wider and safer.