Effect of sputum induction on spirometric measurements and arterial oxygensaturation in asthmatic patients, smokers, and healthy subjects

Background: Sputum production induced by inhalation of hypertonic saline so lution has been proposed as a technique to collect secretions and inflammat ory cells from the airways of subjects with bronchial asthma or with a hist ory of smoking. The aim of this study was to determine the effect of a sput um induction procedure on spirometric:results and arterial oxygen saturatio n (SaO(2)) in asthmatic patients, smokers, and healthy subjects. Methods: We recruited 14 subjects suffering from asthma (11 men and 3 women ; age range, 18 to 49 years), 14 subjects with a history of smoking (5 men and 9 women; age range, 23 to 64 years), and 9 healthy volunteers (7 men an d 2 women; age range, 28 to 54 years). To obtain a sample of induced sputum , all subjects inhaled a mist of 3% hypertonic saline solution nebulized fo r 5 min and repeated the cycle no more than four times. Asthmatic patients were pretreated with 200 mu g salbutamol (inhaled). During sputum induction , the! transcutaneous SaO(2) was continuously measured and baseline, fall, and the differences between baseline and fall Sao, were recorded. Additiona lly, we measured the duration of mild desaturation (change in SaO(2), < 4%) and of marked desaturation (change in SaO(2), > 5%) in each subject. Final ly, baseline FEV1 and changes in FEV1 as a percentage of baseline values we re recorded in all subjects. Results: We found that baseline and fall Sao, values-for the three groups w ere similar. However, in each group a significant mean change in SaO(2) was evident during sputum production (asthmatic patients, 6.0%; smokers, 5.3%; healthy subjects, 6.0%). Moreover, the mean durations of mild desaturation were 7 min, 21 s in asthma patients; min, 24 s in smokers; and 7 min, 16 s in healthy subjects. Similarly, the durations of marked desaturation were 1 min, 25 s in asthmatic patients, 1 min, 19 s in smokers, and 1 min, 21 s in healthy subjects. The mean (+/- SD) fall in FEV1 was not statistically d ifferent among the three groups(asthmatic patients, 1.36 +/- 5.6%; smokers, 7.58 +/- 11.76%; and healthy subjects, 0.05 +/- 9.6%). However, one smoker did experience excessive bronchoconstriction (fall in FEV1, > 20%). Conclusions: This study demonstrated a significant and comparable fall in S aO(2) during sputum induction by inhalation of hypertonic saline solution i n:asthmatic patients, smokers, and healthy subjects. The results suggest th at subjects who are hypoxemic before sputum induction require SaO(2) monito ring during the procedure.