Safety of sputum induction with isotonic saline in adults with acute severe asthma

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 FEV. 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 greater than or equal to 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 beta (2)-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 branchoconstriction to occur but this can be managed safely with minimal discomfort to subjects.