Evaluating Bronchodilator Response in Patients With Bronchiectasis

Bronchiectasis are defined as irreversible dilatation of the bronchial tree. Patients with bronchiectasis suffer of chronic cough and sputum production, and are predisposed to recurrent airway infections. Many systemic diseases can cause bronchiectasis: cystic fibrosis (CF), primary ciliary dyskinesia (PCD), primary immune deficiencies (PID) and idiopathic bronchiectasis (IB) represent a significant proportion of patients with bronchiectasis starting in early age.

Pulmonary function testing (PFT) and specifically forced expiratory volume in one second (FEV1) is a common modality used to estimate lung disease progression and pulmonary exacerbations in patients with bronchiectasis. Although patients with bronchiectasis tend to have non reversible obstructive patterns on pulmonary function tests (PFTs), reversible obstruction is not uncommon. While bronchodilator response (BDR) is a main characteristic of asthma, the pathophysiology causing this phenomenon in bronchiectasis patients is less clear. The improvement in FEV1 after inhalation of bronchodilators can be attributed to bronchodilation or improved mucociliary clearance. It can be speculated that for some of the bronchiectasis patients, hyper-reactive airways or asthma can contribute to the reversible pattern. Despite the wide scale use of bronchodilators in bronchiectasis the evidence for its efficacy is lacking. While some studies found that BDR is associated with more severe disease, other studies did not find such associations.

According to ATS/ERS statement, the proper way to determine BDR, is by first recording three attempts of spirometry, then delivering bronchodilators, and after a waiting time, obtaining again at least three attempts of spirometry. The most resent ATS/ERS technical standard suggests that change of >10% relative to the predicted value for FEV1 or forced vital capacity (FVC) be considered a positive BDR.

While in most scenarios it is reasonable to assume that the change in FEV1 measured after the waiting time can be attributed solely to the affect of bronchodilators, this is not necessarily the case in bronchiectatic diseases. Theoretically, in bronchiectasis, the forced expiration maneuver used in spirometry testing can potentially cause changes in lung function, for example by inducing cough and mobilization of sputum. Evidence for this assumption can be seen in that respiratory therapy in terms if positive expiratory pressure (PEP) therapy can improve various parameters of lung function when tested again closely after the therapy.

The goal of this study is to determine if bronchodilator response in bronchiectatic disease might be influenced by other factors apart from the direct effect of bronchodilators. Secondary objectives are to assess if BDR is associated with age, gender, specific bronchiectatic disease, baseline FEV1, and other clinical factors such as sputum cultures, IgE levels, eosinophil levels, computed tomography (CT) score, family history of asthma and use of inhaled steroids.