May Addison K, Brady Jacob S, Romano-Keeler Joann, Drake Wonder P, Norris Patrick R, Jenkins Judith M, Isaacs Richard J, Boczko Erik M
Division of Trauma and Surgical Critical Care, Vanderbilt University, Nashville, TN.
Division of Trauma and Surgical Critical Care, Vanderbilt University, Nashville, TN.
Chest. 2015 Jun;147(6):1494-1502. doi: 10.1378/chest.14-1687.
Ventilator-associated pneumonia (VAP) remains a common complication in critically ill surgical patients, and its diagnosis remains problematic. Exhaled breath contains aerosolized droplets that reflect the lung microbiota. We hypothesized that exhaled breath condensate fluid (EBCF) in hygroscopic condenser humidifier/heat and moisture exchanger (HCH/HME) filters would contain bacterial DNA that qualitatively and quantitatively correlate with pathogens isolated from quantitative BAL samples obtained for clinical suspicion of pneumonia.
Forty-eight adult patients who were mechanically ventilated and undergoing quantitative BAL (n = 51) for suspected pneumonia in the surgical ICU were enrolled. Per protocol, patients fulfilling VAP clinical criteria undergo quantitative BAL bacterial culture. Immediately prior to BAL, time-matched HCH/HME filters were collected for study of EBCF by real-time polymerase chain reaction. Additionally, convenience samples of serially collected filters in patients with BAL-diagnosed VAP were analyzed.
Forty-nine of 51 time-matched EBCF/BAL fluid samples were fully concordant (concordance > 95% by κ statistic) relative to identified pathogens and strongly correlated with clinical cultures. Regression analysis of quantitative bacterial DNA in paired samples revealed a statistically significant positive correlation (r = 0.85). In a convenience sample, qualitative and quantitative polymerase chain reaction analysis of serial HCH/HME samples for bacterial DNA demonstrated an increase in load that preceded the suspicion of pneumonia.
Bacterial DNA within EBCF demonstrates a high correlation with BAL fluid and clinical cultures. Bacterial DNA within EBCF increases prior to the suspicion of pneumonia. Further study of this novel approach may allow development of a noninvasive tool for the early diagnosis of VAP.
呼吸机相关性肺炎（VAP）仍是重症外科患者常见的并发症，其诊断仍存在问题。呼出气体中含有反映肺部微生物群的雾化液滴。我们推测，吸湿冷凝湿化器/热湿交换器（HCH/HME）过滤器中的呼出气体冷凝液（EBCF）会含有细菌DNA，其在质量和数量上与因临床怀疑肺炎而获取的定量支气管肺泡灌洗（BAL）样本中分离出的病原体相关。
纳入48例在外科重症监护病房接受机械通气且因疑似肺炎接受定量BAL（n = 51）的成年患者。按照方案，符合VAP临床标准的患者接受定量BAL细菌培养。在进行BAL之前，立即收集时间匹配的HCH/HME过滤器，通过实时聚合酶链反应研究EBCF。此外，对BAL诊断为VAP的患者连续收集的过滤器便利样本进行分析。
51份时间匹配的EBCF/BAL液样本中有49份在已鉴定病原体方面完全一致（κ统计一致性> 95%），且与临床培养结果高度相关。配对样本中定量细菌DNA的回归分析显示具有统计学意义的正相关（r = 0.85）。在一个便利样本中，对连续的HCH/HME样本进行细菌DNA的定性和定量聚合酶链反应分析显示，在怀疑肺炎之前细菌载量增加。
EBCF中的细菌DNA与BAL液及临床培养结果高度相关。在怀疑肺炎之前，EBCF中的细菌DNA会增加。对这种新方法的进一步研究可能会开发出一种用于VAP早期诊断的非侵入性工具。
