The Tolerability and Safety of Repeated Sputum Induction in Patients with Moderate to Severe Chronic Obstructive Pulmonary Disease

Abstract

Background: Sputum induction is a method used over the years to investigate airway inflammation in patients with asthma and chronic obstructive pulmonary disease (COPD), to establish correct disease phenotype. Sputum production and expectoration are induced by inhaling hypertonic saline, which can also provoke adverse effects such as bronchoconstriction, lung hyperinflation, and dyspnea. The aim of this retrospective study was to assess the tolerability and safety of sputum induction in patients with more severe COPD stages. Methods: A total of 76 sputum inductions were performed in 20 patients with moderate or severe COPD (median FEV1 1.6 L 95%CI 1.47-1.71, or 51% 95% CI 47-54% of predicted) over a period of 32 days. Unique advantage of this study is multiple sputum induction in same patient. After premedication with 200 µg salbutamol, subjects inhaled increasing concentrations of aerosolized saline (0.9%, 3%, 4% and 5%), each for 7 minutes. FEV1 was recorded prior to induction and after each inhalation interval. Results: The median fall of FEV1 at the end of sputum induction was 127 mL (95%CI 90-176 mL) or 10% (95%CI 7-11%) from baseline post-bronchodilator value. In 11 cases (14%) the procedure was terminated due to an excessive bronchoconstriction (fall in FEV1>20% from baseline). None of the subjects reported adverse events. Conclusions: Sputum induction is safe and well tolerated by patients with moderate to severe COPD, which supports its use in clinical and research practice. Patients with a more severe airway obstruction may have a higher risk of excessive bronchoconstriction, precaution measures should be anticipated in those patients.