Cause Of Bronchial Provocation Test In The Diagnosis Of Chronic Cough

ObjectiveThe diagnosis and treatment of cough failure will cause: antimicrobial drugs abuse, For diagnosis of unclear and repeated inspection, Not only to increase the patient suffering, and increased its economic burden. It has been confirmed that duffing forced-oscillation technical judgement asthma patients' bronchial proocation tests is reliable, but its specificity of asthma and diagnosis standard still need further discussion.The objective of this study was to detect the airway sensitivity with Astograph method, as well as to explore its significance in the etiological diagnosis of chronic cough.MethodsChinese Medicine Respiratory Diseases Asthma Study Group Proposed the diagnostic criteria for chronic cough in 2009:(1) Cough time is at least 8 weeks; (2) Cough is main complain or the only symptom; (3) Normal chest X-ray examination. 231 volunteers were involved in this study, According to the criteria of chronic cough diagnostic,231 patients with chronic cough were involved in our study. The test is after the approval of the Hospital Clinical Medical Ethics Committee and obtaining all participants' Informed consent.The routine pulmonary function tests were held under the instruction of Practical Guide for pulmonary function tests,1.Basic clinical characteristics were first, after which the volunteers were taught how to follow our instructions during a pulmonary test. Routine pulmonary function was tested with a spirograph(Master Screen-PFT Jaeger Co, Hoechberg,Germany) to decide whether a volunteer fit the airway provocation test. The routine pulmonary function tests were held under the instruction of Practical Guide for pulmonary function tests, each volunteer was repeatly tested three times, and the experimental variation should be no more than 5%, from which the best values were chosen; The airway provocation test was held with an astograph (Astograph Jupiter-21, Japan),in which escalatory doses of methacholine was inhaled to provoke constriction of airways. Dmin value were recorded at the same time, When the respiratory resistance increased to twice of the basic respiratory resistance (Rrs cont) and Dmin≤15 was a positive standard.2.According to the principle of voluntarily,15 participants whose bronchial provocation test were positive with Astograph were asked to take Spirometry and impulse oscillation measurements before and after the standard methacholine provocation test (APS aerosol excitation system, Hoechberg,Germany). The IOS is after the Astograph more than 24 hours.And to avoid the effect of forced expiratory we follow the order: inhaling methacholine, determinating of respiratory resistance,FEV1,PEF and repeat the above process. Those whose BPT positive were given inhaled salbutamol after IOS determination.3.Following up the volunteers in- the next 6 months. Results1. Among 231 volunteers involved in our study,117 cases (50.6%)were found BPT positive, while 114 were negative. Among the 117 positive cases.There was no significant difference in male and female group about BPT positive rate and CVA percentage.110 volunteers were diagnosed as CAV, which comprised 68.6% of the total cough cases, and 5 positive cases were diagnosed as postinfectious cough, while the left 2 were COPD patients of zero grade. The highest CAV occurance rate was seen in group aged below 30 years, while the lowest occurance rate(23.1%) was seen in group aged over 60 years. The specificity of BPT was 94.0% to the diagnosis of CVA. In the 110 negative cases,41 cases (17.7%)were diagnosed as UACS,25 cases (10.8%)were diagnosed as EB,22 cases (9.5%)were due to ACEI drugs intake, while the etiological diagnosis of the left 2 cases was still unknown.2. We used 1 unit,3 unit,6 unit,15 unit of Dmin as the critical value. The diagnosis of asthma sensitivity and specificity were different. When we make Dmin≤ 6unit as the positive criteria for the diagnosis of asthma, the sensitivity was 74.1% and the specificity was 90.5%.3.15 patients received impulse oscillation determination, confirmed by follow-up 10 patients were asthma, and 5 cases were non-asthmatic patients,whose bronchial provocation test were positive, before the standard provocative test there was no significant difference in R5, R20, X5,FEV1, FVC, PEF (P>0.05) both in Asthma group (10 cases) and non-asthmatic group (5 cases). After the standard provocative test there was a significant difference in R5, FEV1, PEF both in Asthma group (10 cases) and non-asthmatic group (5 cases). Dmin value in asthma group is much lower in non-asthmatic group.4. CVA, postinfectious cough and COPD are the three main causes of chronic cough with positive BPT, but they also have their own characteristics. CVA group had an evident lower Dmin and Cmin than the other two groups(P<0.001). There was also a significant difference in the appearance of dose-resistance curve, mainly in the increasing rate of airway resistance. In CVA group, the resistance increased in a dynamic type, but fell rapidly after inhalation of bronchodilators, and the dose-resistance curve looked like an isosceles triangle, however, in COPD and postinfectious goup, the resistance increased slowly, especially in the postinfectious goup, it even showed an appearance similar to BPT negative curve.Conclusion1. Astograph and IOS were the same predictive value in BPT. Astograph method helps to diagnose the cause of airway hyperresponsiveness.2. BPT was highly specific to CVA diagnosis, thus, developing CVA screening in chronic cough patients could help to make a correct diagnosis as well as give a precise treatment as early as possible, so that cut off its way towards a characteristic asthma.3. A great variety of factors can lead to chronic cough, and two or more factors may exist in one single patient at the same time, thus, careful follow up should be payed more attention during the etiological diagnosis of chronic cough, and if the therapy is not curative, it is necessary to alter the treatment timely.