| Objective: Using mechanical compression method to prepare guinea pig model of pressure ulcers,To explore the effects and mechanisms of vacuum sealing drainage(VSD)technique in facilitating the healing of stage 3 pressure ulcers in guinea pigs model.Methods: 1)Modelling: healthy male white guinea pigs weighting 600-670 g were selected and intraperitoneally anesthetized by injecting 10% chloral hydrate(300mg/kg).The IRI stage 3 pressure ulcer was induced on the right trochanter of guinea pigs by exerting repeated pressure.2)Grouping and implementing intervention: this experiment is divided into a blank group(n=20),a conventional group(n=20),and a VSD group(n=20).There was no intervention or treatment was provided to blank group.The conventional group received conventional care with sterile porous polyurethane sponge dressing and gauze covering,and daily sterile application replacement.The VSD group received conventional dressing,VSD intervention with sterile porous polyurethane sponge dressing,the paster closed surgery,negative pressure treatment,and daily sterile application replacement.3)Evaluation:randomly selected 5 guinea pigs from the 3 groups respectively to observe their healing condition;shrinkage in wound area;pathological changes of wound tissue;bacterial content of wound tissue;detecting the guinea pig serumusing of nitric oxide synthase(NOS)and superoxide dismutase(SOD)content;detecting CD34 and vascular endothelial growth factor(VEGF)in wound area respectively at the 1 day,3 days,7days and 11 days after intervention.Calculating the microvascular density(MVD)and the average optical density value(MOD)by the image pro plus graphic processing software.Results: 1)Wound observation: at 1 day after more hematodes exudate and obvious skin tissue oedema were observed in the conventional group and blank group,By contrast,the wound hematodes exudate of VSD group reduced compared to that before intervention.At3 days after intervention,in the blank group,the wound was dark and dull;more blood exudate was secreted by comparing to other two groups;and no obvious change was found in terms of tissue oedema.In the conventional group,the wound turn to be red;less blood exudate was found compared to blank group;the skin tissue oedema was improved than that before intervention;and the wound began to shrink gradually.The wound in the VSD group turned to be red,with a small amount of red exudate.Comparing to conventional group and blank group,the skin tissue oedema in the VSD group was improved,with scattered granulation tissue growth and rapid wound contraction.At 7days in blank group darkened and hardened with a small number of exudate.Moreover,the tissue oedema reduced than that before intervention;and the wound shrink gradually.In the conventional group,the wound was seen red with less exudate;though there was still oedema on the tissue,there was a small amount growth in granulation tissue.By comparison,the wound in the VSD group,the wound was seen ruddy;no exudate and obvious tissue oedema were observed;large amount of granulation tissue growth and a significant wound shrinkage were found.At 11 days after intervention,in the blank group,a small amount of blood exudation could be seen after acupuncturing;also,an improvement of tissue oedema was found than before.But the shrinkage of wound was delayed compared to other two groups.In conventional group,the wound was smooth and red,and with obvious growth of granulation tissue.However,the wound shrinkage was slower than that in the VSD group.The wound healed with no exudation in the VSD group.2)Wound area shrinkage rate: there were no statistical differences among the three groups at 1 day after intervention(P>0.05).At 3 days after implementing intervention,a further comparison showed that the shrinkage rate was higher in conventional group compared to blank group(P<0.01),and the shrinkage rate in VSD group was higher than that of the conventional group and blank group(P<0.01).At 7 days and 11 days after intervention,conventional group had a more improved shrinkage rate than that in the blank group(P<0.01).In addition,higher shrinkage rate of wound area was found in the VSD group(P<0.01).3)Pathological changes in wound tissue: At 1 day after intervention,each group experienced a large number of inflammatory cell infiltration and significant subcutaneous tissue oedema.Specifically,the infiltration of inflammatory cells and the oedema condition in the VSD group were smaller than other two groups,and had a certain amount of granulation tissue growth.At 3 days,there was a promotion in the infiltration of inflammatory cells and tissue oedema among groups.This improvement was even greater,and the growth of granulation tissue was more obvious in the VSD group.At 7 days,cells infiltration and tissue oedema were in better condition than conventional and blank groups.At 11 days,there was still inflammatory cell infiltration in the blank group.In conventional group,a great number of granulation tissue hyperplasia and vitreous degeneration were found.In the VSD group,skin tissue was healed obviously.Scars were formed with hyperplasia from subcutaneous collagen fiber.4)Bacterial content of wound tissue: at 1 day,3,7,and 11 days,the amount of bacteria in wound tissue in the conventional group was also lower by comparing to blank group(P<0.01).And this objective was significantly lower in the VSD group than the conventional group and blank group(P<0.01).5)Serum content of NOS and SOD:(1)the content of NOS in the conventional group was significantly lower than that in the blank group(P<0.01),but higher than that in the VSD group(P<0.01).(2)On the contrary,the result found that the content of SOD was significantly higher than that in the blank group(P<0.01),but lower than that in the VSD group after all(P<0.01).6)CD34 in wound area and MVD:The positive expression of CD34 gradually increased in each group after intervention(VSD group >conventional group>blank group).Results of MVD from VEGF was higher in the conventional group when compared with blank group(P<0.01).This figure showed that the MVD was significantly higher in the VSD group than that in other groups(P<0.01).7)VEGF in wound area and MOD: The positive expression of VEGF gradually increased in each group after intervention(VSD group >conventional group>blank group).Results of MOD from VEGF was higher in the conventional group when compared with blank group(P<0.01).This figure showed that the MOD was significantly higher in the VSD group than that in other groups(P<0.01).Conclusion: This study suggested that the VSD is effective for IRI stage 3 pressure ulcers in guinea pigs model by promoting the healing of wound tissue,improving the wound area shrinkage,reducing the pathological impairment in wound area,and inhibiting the growth of bacteria in wound tissue.The mechanisms of this intervention may possibly be associated with inhibiting the level of NOS in wound tissue,increasing the level of SOD,and enhancing the expression of CD34 and VEGF in granulation tissue. |
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