Study objectives: Induced sputum is used to investigate pulmonary diseases. Low-output ultrasonic nebulizers have become available and have potential advantages over high-output nebulizers. We hypothesized that a low-output nebulizer would give comparable results to a high-output nebulizer, with an acceptable safety profile.
Design: Randomized, crossover study.
Setting: University teaching hospital.
Participants: Ten normal subjects and 10 patients with COPD.
Interventions: Participants attended for sputum induction on two occasions in random order using low-output and high-output nebulizers.
Measurements and results: Lung function and oxygen saturation were measured during sputum induction, and tolerability of the procedure was assessed. Cell counts, interleukin 8, and neutrophil elastase were measured in sputum. Use of the high-output nebulizer resulted in a greater FEV1 (mean ± SEM, 0.29 ± 0.04 L vs 0.21 ± 0.04 L; p = 0.04) and percentage drop in FEV1 (25.8 ± 2.6% vs 19.5 ± 2.9%, respectively; p = 0.02) compared with the low-output nebulizer in patients with COPD. There was a shorter tolerated nebulization time with the high-output nebulizer compared with the low-output nebulizer: 12.7 ± 2.0 min vs 16.5 ± 1.8 min, respectively (p = 0.02). Modified Borg scores were lower with the low-output nebulizer than the high-output nebulizer in normal subjects: median, 0 (interquartile range [IQR], 0 to 1) vs median, 1.5 (IQR, 0 to 2), respectively (p = 0.05). There were no differences in cell counts and soluble markers of inflammation.
Conclusions: The low-output ultrasonic nebulizer is comparable to high-output nebulizer for cellular and soluble markers of inflammation, results in a smaller reduction in FEV1, is better tolerated, and is a suitable tool for investigating airway inflammation in patients with COPD.