COMPARISON OF SPONTANEOUS AND INDUCED SPUTUM FOR INVESTIGATION OF AIRWAY INFLAMMATION IN CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Background-Although sputum induction is used as a technique to investi gate lower airway inflammation in asthmatic subjects, advantages over spontaneous sputum in patients with chronic obstructive pulmonary dise ase (COPD) have not been investigated. Methods-Samples of spontaneous sputum and sputum induced with 3% hypertonic saline for 14 minutes wer e collected from 27 patients with chronic obstructive pulmonary diseas e (COPD) who usually produced spontaneous sputum. Spirometric indices and oxygen saturation (Sao(2)) were measured at seven minute intervals . The spontaneous, seven and 14 minute sputum samples were analysed fo r total and differential cell. counts, cell viability, and interleukin 8 levels. Results-Analysis of the sputum revealed that median cell. v iability was higher hn the seven minute (62.8%; p = 0.004) and 14 minu te (65%; p = 0.001) induced sputum samples than in spontaneous sputum (41.2%). There was no significant difference in total and differential cell counts or in interleukin 8 levels between spontaneous and induce d sputum. During the sputum induction procedure the mean (SD) fall in forced expiratory volume in one second (FEV1) was 0.098 (0.111) 1 (p < 0.001) and in forced vital capacity (FVC) was 0.247 (0.233) 1 (p < 0. 001). There was a small but significant fall in Sao(2) during sputum i nduction (p = 0.03). Conclusions-Induced sputum contains a higher prop ortion of viable cells than spontaneous sputum. There are no significa nt differences between the sputum samples obtained at seven minutes an d at 14 minutes of hypertonic saline nebulisation. Sputum induction is safe and well tolerated in patients with COPD.