呼吸机相关性肺炎--胃肺感染路径的前瞻性研究

目的　探讨胃肺感染路径在呼吸机相关性肺炎 (VAP)发生中的作用 ,为预防和治疗VAP提供科学依据。　方法　选择 4 3例接受机械通气 (MV)的患者 ,采用随机自身前后对照法 ,用 99m锝五乙酸 (99m Tc DTPA)标记胃内容物后 ,测定患者平卧或半卧位时口咽部分泌物及深部气管吸出物的放射性水平。留取口咽部、气管吸出物和胃液作培养 ,1次 2d。可疑VAP者取支气管肺泡灌洗液 (BALF)作细菌定量培养。采用稀有限制区聚合酶链反应 (IRS PCR)法对同一VAP患者胃内定植菌与VAP致病菌进行细菌同源性鉴定。测定BALF中分泌型免疫球蛋白A(sIgA)含量。　 结果　MV患者胃食管返流率较高 (89.7% ) ,误吸率相对较低 (2 8.5 % )。患者误吸率和深部气管吸出物的放射性水平 ,平卧位时均显著高于半卧位 (P <0.0 1);胃内定植菌与VAP致病菌有较高的同源性 (5 5 8% ) ;VAP患者BALF中sIgA含量显著低于非VAP患者 (P <0.0 1)。　结论　MV患者普遍存在胃、食管返流和误吸 ;胃内定植菌是VAP病原菌的重要来源之一 ;BALF中sIgA含量降低是MV患者发生VAP的危险因素。

Prospective study on the gastro-pulmonary infection route of ventilator-associated pneumonia

OBJECTIVE: To explore the role of gastro-pulmonary infection route in the development of ventilator-associated pneumonia (VAP), so as to improve the management of VAP. METHODS: Forty-three patients who received mechanical ventilation (MV) were enrolled in the study. Intra-gastric contents were labeled with (99)mTc-DTPA. Randomized two-period crossover trial was employed to determine the radioactive level in the oropharyngeal and bronchial secretion when patients were in supine or semi-reclining position. Gastric juice, oropharyngeal secretion and tracheal lavage fluid were collected for bacterial culture every other day. Bronchoalveolar lavage fluid (BALF) was harvested from those suspected of VAP for quantitative bacterial culture. Infrequent-restriction site amplification (IRS-PCR) was employed in the identification of the identity of the bacteria from intra-gastric colonization with those causing VAP. The sIgA content in the BALF was determined. RESULTS: The gastroesophageal regurgitation rate was higher (89.7%) with lower aspiration rate (28.5%) in patients receiving MV. Moreover, the aspiration rate and the radioactivity of deep tracheal aspirates in patients in supine position were significantly higher than those in semi-reclining position (P < 0.01). There was high homology of the bacteria isolated from intra-gastric colonization with that causing VAP (55.8%). The sIgA content in BALF in VAP patients was evidently lower than that in non-VAP patients (P < 0.01). CONCLUSION: Regurgitation and aspiration of stomach contents are very common in patients receiving MV. Intra-gastric colonized bacteria might be one of the important origins causing VAP. The lowering of sIgA in BALF in patients with MV could be a risk factor for VAP.