Background: Sputum induction is a safe and effective technique to study airway inflammation in stable asthma. However, it has the potential to induce bronchospasm and the safety and efficacy of the technique in acute asthma has not been determined.
Objective: The objective of this study was to evaluate the safety and efficacy of a protocol to induce sputum using isotonic saline in adults with acute exacerbations of asthma.
Methods: Adults (n = 47) presenting to the emergency room with acute asthma and an FEV1 > 1.0 L underwent supervised sputum induction with 0.9% saline delivered by an ultrasonic nebuliser. Induction was ceased if there was a fall of 20% or greater from baseline FEV1.
Results: Subjects had moderate to severe exacerbations of acute asthma. An adequate sputum sample was obtained in 87% of subjects. Four subjects ceased induction because of symptom distress. There was a fall > or = 20% in 28% of subjects. Bronchoconstriction was successfully reversed by salbutamol in all subjects. Predictors of significant bronchoconstriction were older age, use of ingested corticosteroids, and a requirement for high-dose nebulized salbutamol for the exacerbation. Maintenance long-acting beta2-agonist therapy protected against bronchoconstriction during sputum induction.
Conclusions: Sputum induction in acute asthma using isotonic saline is highly efficacious in obtaining an adequate sputum sample. There is the potential for significant bronchoconstriction to occur but this can be managed safely with minimal discomfort to subjects.