The role of the methacholine inhalation challenge in adult patients presenting with chronic cough.

One hundred and twenty two patients who were presenting with chronic persistent cough for more than 3-4 weeks were studied. Using anatomical and stepwise approach, we could identify the cause of chronic cough in 96% of the patients. The most common causes were due to postnasal drip syndrome (PND) (45%) and bronchial asthma (26%). We also demonstrated the important role of methacholine inhalation challenge in the diagnostic work up. The procedure could identify the patients who had bronchial hyperresponsiveness (BHR) in 52% of the cases. The severity degree of the BHR was classified into three levels. Mild or nonspecific BHR was defined as PC20 16-25 mg/ml. This could be found in many diseases such as PND and bronchiectasis. Moderate degree of BHR (PC20 8-16 mg/ml) was found in patients with PND and asthma. PC20 of less than 8 mg/ml was considered to be the most severe degree and it seemed to be specific for the diagnosis of asthma (positive predictive value 100%). Other condition that caused chronic cough were drug-induced, especially angiotensin-converting enzyme inhibitors, gastroesophageal reflux disease (GERD), idiopathic pulmonary fibrosis, subgottic cancer and idiopathic cough. These conditions may require invasive diagnostic work up, such as fiberoptic bronchoscopy and tissue biopsy. The treatment of chronic cough was according to the etiology. Thus, the patients presenting with chronic cough should be investigated to identify the cause, and it was not just only the administration of cough suppressant drugs in these patients.

Methacholine inhalation challenge in patients with chronic cough induced by angiotensin-converting enzyme inhibitors.

Angiotensin-converting enzyme inhibitors (ACEI) cause cough in some patients, but the mechanism of this side effect is not clear. Five patients (group I) who had developed chronic cough induced by ACEI were evaluated to determine the bronchial hyperreactivity (BHR) by challenge with methacholine inhalation using a reservoir method at Respiratory Unit, Chulalongkorn Hospital University. Five patients (group II) who did not experience coughing associated with ACEI were also challenged as controls. The results revealed that two patients (40%) in group I demonstrated BHR with the mean PC20 at 15 mg/ml of methacholine solution. On the other hand, none of the patients in group II disclosed BHR. We concluded that coughing during ACEI therapy may be due to an increased inflammatory state in the airway in some susceptible subjects.

Effect of inhaled corticosteroids on bronchial hyperresponsiveness in patients with mild asthma.

We studied the effect of inhaled budesonide on bronchial hyperresponsiveness (BHR) in twenty mild asthmatic patients. The study was conducted as a randomized, double-blind, placebo-controlled study. Before entering the study, the patients performed methacholine inhalation challenge (MIC) using a reservoir method to assess BHR. Then, they were randomly allocated to receive budesonide turbuhaler (200 micrograms/dose) or placebo turbuhaler two inhalations, twice daily for eight weeks. During the study, each patient recorded daily asthma score and daily number of puffs of beta 2 agonist and they were assessed at weeks 4 and 8. At the end of the treatment, MIC was repeated again. Patients receiving budesonide showed a significant improvement in airway responsiveness compared with those receiving placebo (p < 0.05). They also showed a significant improvement in asthma severity score and a significant decrease in beta 2 agonist bronchodilator use. This study also suggested that inhaled corticosteroids may be the primary treatment in patients, even with mild asthmatic and well-controlled symptoms.

Standardization of methacholine inhalation challenge by a reservoir method.

Standardization of methacholine inhalation challenge (MIC) by a reservoir method was performed at Respiratory Unit, Chulalongkorn Hospital. One hundred subjects, including 20 non-smoking healthy subjects, 20 patients with isolated chronic cough, 20 patients with isolated allergic rhinitis, 20 patients with stable chronic obstructive bronchitis, and 20 patients with mild bronchial asthma, were scheduled to perform the test. The aerosolized methacholine was produced by an atomized nebulizer of the Provocation test I (Pari-Starnberg) and the aerosol was kept in a reservoir bag. It was inhaled by each subject via a slow vital capacity. Increasing concentrations of methacholine (0, 0.5, 1, 5, 10, and 25 mg/ml were used. None of the healthy subjects had increased bronchial hyperresponsiveness (BHR). Sixty percent of patients with chronic cough, 60% of patients with allergic rhinitis, 95% of patients with chronic obstructive bronchitis, and 100% of patients with asthma were found to be positive in the MIC tests. No serious effect from methacholine during and after the tests was found. It was concluded that MIC can be easily performed by a reservoir with reproducible results to demonstrate BHR.