Study On The Relationship Between Gastric Colonization And Ventilator Associated Pneumonia Occur In Patients With Chronic Obstructive Pulmonary Disease And Several Of Its Influential Factors

Objective:In order to provide some clues to keep the chronic obstructive pulmonary disease(COPD)patients undergoing mechanical ventilation away from ventilator associated pneumonia(VAP),we set out to investigate:①the part the intragastric bacteria plays in the pathogenesis of VAP in COPD patients,②the influences of the physiochemical features of the gastric fluid,including pH value,SIgA and TBA level on the colonization of the intragastric bacteria and③the effects of acid inhibitors, mucosal protective agents and the type of nutrition support on the above mentioned features of the gastric fluid of the mechanical ventilated COPD patients.Methods:35 COPD patients undergoing mechanical ventilation were enrolled in our study.Bacteriological examination was made for the samples of lower respiratory tract,gastric fluid and pharyngeal swab by means of semi-quantitative cultivation. SIgA and TBA level in the gastric fluid was measured by means of double antibody sandwich radiation immunological test and enzymatic cycling assay,respectively.The pH value of the gastric fluid was determined by precision pH test paper.The administration of acidic inhibitor,mucosal protective agents and the type of nutritious support was recorded,and the occurrence of VAP was assessed.All the experimental data were processed and analyzed by SPSS13.0 statistic software package.Results:①Of all the 121 gastric fluid samples obtained from the 35 patients, intragastric bacteria colonization was spotted in 40 samples belonging to 21 cases. Totally,45 bacterial strains were isolated,which were mainly Acinetobacter baumannii,Klebsiella pneumoniae,Pseudomonas aeruginosa,Escherichia coli and Stenotrophomonas maltophilia.Among all these colonized cases,16(16/21) developed VAP,which was significantly higher than the non-colonized group(5/14, p＜0.05).In 6 cases,6 strains manifested a colonization order of gastric cavity, oropharynx and lower respiratory tract.All the colonies obtained from various positions share the same antibiotic sensitive spectrum,indicating the homogeneity among them.②The pH value and TBA level of the gastric fluid from the colonized group(5.65±1.03 and 57.06±54.75μmol/L,respectively)was significantly higher than that of the non-colonized group(4.56±1.51 and 25.36±16.62μmol/L,respectively) (p＜0.01).The frequency of omeprazole administration in the colonized group(22/40) was higher than that of the non-colonized group(28/81,p=0.032).The SIgA level in the gastric fluid of the colonized group(12.67±20.1μg/L)was higher than that of the non-colonized group(12.18±14.22μg/L),although the difference was statistically insignificant(p＞0.05).③Significant difference was spotted between the pH value of the gastric fluid from the 2 omeprazole treatment groups(group A,5.50±0.69;group B,6.32±0.57)and the 2 non-omeprazole treatment groups(group C,3.30±0.67;group D,4.23±1.41)(p＜0.01).No significant difference was found within the 2 omeprazole treatment groups and the 2 non-omeprazole treatment groups(p＞0.05).There was no significant difference among the four groups in TBA level,which was 43.42±58.94, 31.78±23.18,20.14±12.86,and 36.39±30.25μmol/L for group A,B,C and D, respectively.The SIgA levels in the gastric fluid of the 2 TPN groups(group A, 3.50±5.13μg/L and group C,1.97±0.896μg/L)were significantly lower than those of the 2 EN groups(group B,24.27±22.30μg/L and group D,13.81±15.45μg/L) (p＜0.01),while no significant difference existed within the 2 TPN groups and the 2 EN groups(p＞0.05).④No correlations had been spotted between pH and TBA (r=0.175,P=0.055),pH and SIgA(r=0.169,P=0.064)and TBA and SIgA(r=0.094, P=0.307)in the gastric fluid samples.Conclusions:①The positive cultivation results of pathogenic bacteria in the gastric fluid,pharyngeal swabs and the lower respiratory tract samples revealed a colonization order of gastric cavity,oropharynx and lower respiratory tract and further demonstrated that retrogradation and aspiration was one of the infection routes of VAP in mechanical ventilated COPD patients.②Higher pH value of gastric fluid was a risk factor of intragastric bacteria colonization and omeprazole could increase the risk of the colonization by elevating this index,which indicated that compared with omeprazole,mucosal protective agent aluminum phosphate could provide more protective effects against VAP.③The gastric fluid pH value of the mechanical ventilated COPD patients trended to be much higher,which could be attributed to the influential factors such as morbid state,nasogastric feeding,age and gastroduodenal reflux.④TPN could decrease the SIgA level in the gastric fluid of mechanical ventilated COPD patients.However,since the SIgA level was affected by not only the type of nutrition support but also other factors such as infection,no difference had been spotted between the colonized and the non-colonized groups.⑤Bile reflux was a risk factor of intragastric bacteria colonization.No correlation existed between TBA level and pH value in gastric fluid.