Background: Microaspiration is often considered a potential cause of cough. The aim of this study was to investigate the relationship between microaspiration, the degree and type of gastroesophageal reflux, and the frequency of coughing in patients with chronic cough. Methods: One hundred patients with chronic cough (mean [± SD] age, 55.8 years [± 11.0 years]; 65 women) and 32 healthy volunteers (median age, 43.5 years [interquartile range (IQR), 30-50.8 years]; 16 women) were recruited. Patients with chronic cough performed 24-h objective cough frequency with simultaneous esophageal impedance/pH monitoring and measurement of pepsin concentrations in sputum and BAL. Twelve healthy volunteers underwent bronchoscopy/BAL, and 20 underwent impedance/pH monitoring. Results: Patients with chronic cough had significantly more reflux episodes than healthy volunteers (median, 63.5 reflux episodes [IQR, 52.5-80.0] vs 59.0 [IQR, 41.8-66.0]; P = .03), although the absolute difference was small, and there was no difference in numbers of events extending into the proximal esophagus (median, 17.2% [IQR, 8.0%-26.0%] vs 20.3% [IQR, 5.1%-32.1%]; P = .36). BAL pepsin levels were also similar in chronic cough to control subjects (median, 18.2 ng/mL [range, 0-56.4 ng/mL] vs 9.25 ng/mL [range, 0-46.9 ng/mL]; P 5.27). Sputum but not BAL pepsin weakly correlated with the number of proximally occurring reflux events(r = 0.33, P = .045) but was inversely related to cough frequency(r = -0.52, P = .04). Sputum pepsin was, therefore, best predicted by combining the opposing influences of cough and proximal reflux(r = 0.50, P = .004). Conclusions: Proximal gastroesophageal reflux and microaspiration into the airways have limited roles in provoking chronic cough. Indeed, coughing appears to be protective, reducing pepsin concentration in the larger airways of patients with chronic cough. Trial registry: ISRCTN Register; No.: ISRCTN62337037; URL: www.isrctn.org.
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机译：背景：微吸通常被认为是咳嗽的潜在原因。这项研究的目的是调查慢性咳嗽患者微吸痰，胃食管反流的程度和类型以及咳嗽频率之间的关系。方法：一百例慢性咳嗽患者（平均[±SD]年龄，55.8岁[±11.0岁]; 65名女性）和32名健康志愿者（中位年龄，43.5岁[四分位间距（IQR），30-50.8岁];招募了16位女性）。慢性咳嗽患者进行24小时客观咳嗽频率，同时进行食道阻抗/ pH监测并测量痰液和BAL中的胃蛋白酶浓度。 12名健康志愿者接受了支气管镜/ BAL，20名接受了阻抗/ pH监测。结果：慢性咳嗽患者的反流发作明显多于健康志愿者（中位数，63.5反流发作[IQR，52.5-80.0] vs 59.0 [IQR，41.8-66.0]; P = .03），尽管绝对差异很小，进入食道近端的事件数量没有差异（中位值为17.2％[IQR，8.0％-26.0％]和20.3％[IQR，5.1％-32.1％]; P = 0.36）。在慢性咳嗽中，BAL胃蛋白酶水平也与对照组相似（中位数为18.2 ng / mL [范围，0-56.4 ng / mL]与9.25 ng / mL [范围，0-46.9 ng / mL]; P 5.27）。痰液但不是BAL胃蛋白酶与近端发生反流事件的数量弱相关（r = 0.33，P = .045），但与咳嗽频率呈负相关（r = -0.52，P = .04）。因此，最好结合咳嗽和近端反流的相反影响来预测痰中的胃蛋白酶（r = 0.50，P = .004）。结论：胃食管反流和向气道的微小抽吸在引起慢性咳嗽方面作用有限。的确，咳嗽似乎具有保护作用，可以降低慢性咳嗽患者较大气道中的胃蛋白酶浓度。试用注册：ISRCTN注册;编号：ISRCTN62337037;网址：www.isrctn.org。
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