[The evaluation of the distal airway inflammation of well controlled asthmatic patients using sputum induction by inhalation of 10% hypertonic saline for 15 minutes].

Background: As the clinical importance of treatment to asthmatic distal airway has been recognized, this study aimed to evaluate the efficacy of the 10% hypertonic saline-induced 15 minutes long-inhaled method to assess the inflammatory situation in the distal airways.

Methods: The subjects were 16 healthy volunteers and 29 patients with well controlled asthma. They inhaled 5% or 10% hypertonic saline for 15 minutes and the sputum induction rates and induced times were measured. We also investigated the values of surfactant protein D (SP-D) and eosinophil cationic protein (ECP) both in early- and late-phase induced sputum, together with pulmonary function indexes, and the patients' impressions of the method.

Results: The sputum induction rates with 10% hypertonic saline inhalation in both healthy volunteer group and well controlled asthmatic patients group were significantly high compared with those with 5% hypertonic saline inhalation; 75.0% (p=0.004) and 75.9% (p=0.007), respectively. The SP-D levels in late-phase sputum in both healthy volunteer group and well controlled asthmatic patients group significantly elevated compared with those in the early-phase: p=0.045 and p=0.007, respectively. The SP-D levels in late-phase sputum significantly correlated to those of ECP in the well controlled asthmatic patients group (r=0.527, p=0.017). The pulmonary function index FEV1.0% of 18 well controlled asthmatic patients (62.1%) attenuated 2.9+/-2.5% soon after finishing the 10% hypertonic saline inhalation, and recovered after an additional 15 minutes rest. 70 approximately 80% of the subjects in both groups answered that they felt no strain in using the inhaled method.

Conclusion: The late-phase sputum obtained by the 10% hypertonic saline-induced 15 minutes long-inhaled method may be useful in evaluating the inflammatory situation in the distal airways.