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

Abstract

Background: Sputum production induced by inhalation of hypertonic saline solution has been proposed as a technique to collect secretions and inflammatory cells from the airways of subjects with bronchial asthma or with a history of smoking. The aim of this study was to determine the effect of a sputum induction procedure on spirometric results and arterial oxygen saturation (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 and 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 for 5 min and repeated the cycle no more than four times. Asthmatic patients were pretreated with 200 microg salbutamol (inhaled). During sputum induction, the transcutaneous SaO(2) was continuously measured and baseline, fall, and the differences between baseline and fall SaO(2) were recorded. Additionally, we measured the duration of mild desaturation (change in SaO(2), < 4%) and of marked desaturation (change in SaO(2), > 5%) in each subject. Finally, baseline FEV(1) and changes in FEV(1) as a percentage of baseline values were recorded in all subjects.

Results: We found that baseline and fall SaO(2) values for the three groups were 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; 8 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 FEV(1) was not statistically different 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 FEV(1), > 20%).

Conclusions: This study demonstrated a significant and comparable fall in SaO(2) during sputum induction by inhalation of hypertonic saline solution in asthmatic patients, smokers, and healthy subjects. The results suggest that subjects who are hypoxemic before sputum induction require SaO(2) monitoring during the procedure.