Dyspnea assessment and adverse events during sputum induction in COPD

BACKGROUND The inhalation of normal or hypertonic saline during sputum induction (SI) may act as an indirect bronchoconstrictive stimulus leading to dyspnea and lung function deterioration. Our aim was to assess dyspnea and adverse events in COPD patients who undergo SI following a safety protocol. METHODS Sputum was induced by normal and hypertonic (4.5%) saline solution in 65 patients with COPD of varying severity. In order to minimize saline-induced bronchoconstriction a protocol based on the European Respiratory Society sputum induction Task group report was followed. Dyspnea change was scored using the Borg scale and lung function was assessed by spirometry and oximetry. RESULTS Borg score changes [median(IQR) 1.5(0-2)] were observed during SI in 40 subjects; 16 patients required temporary discontinuation of the procedure due to dyspnea-general discomfort and 2 did not complete the session due to dyspnea-wheezing. The change in Borg dyspnea score was significantly correlated with oxygen saturation and heart rate changes and with discontinuation of the procedure due to undesired symptoms. 19 subjects presented an hyperresponsive reaction (decline>20% from baseline FEV1). No significant correlation between Borg changes and FEV1 decline was found. Patients with advanced COPD presented significantly greater Borg and oxygen saturation changes than patients with less severe disease (p = 0.02 and p = 0.001, respectively). Baseline FEV1, oxygen saturation and 6MWT demonstrated significant diagnostic values in distinguishing subjects who develop an adverse physiologic reaction during the procedure. CONCLUSION COPD patients undergoing SI following a safety protocol do not experience major adverse events. Dyspnea and oxygen desaturation is more likely to occur in patients with disease in advanced stages, leading to short discontinuation or less frequently to termination of the procedure. Baseline FEV1, oxygen saturation and 6MWT may have a prognostic value for the development of these adverse events and might be useful to be evaluated in advance.