Use of exhaled breath condensate in the study of airway inflammation after hypertonic saline solution challenge

Hypertonic saline solution inhalation is suspected to produce airway inflammation. The aim of this study was to verify this hypothesis by measuring inflammatory markers in exhaled breath condensate (EBC) collected before and after sputum induction with hypertonic and isotonic saline solution. We enrolled 10 patients with asthma, 10 patients with COPD, and 7 healthy subjects with no history of lung disease. Levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α were measured in EBC by a specific enzyme immunoassay kit. Exhaled pH was measured after deaeration/decarbonation by bubbling with argon (350 mL/min) for 10 min by means of a pH meter. Exhaled IL-6 and TNF-α concentrations were greater and pH was decreased compared to baseline after hypertonic saline solution inhalation in each group of subjects studied. No changes were observed following isotonic saline solution inhalation. Concentrations of IL-6, TNF-α, and pH in EBC correlated. These findings suggest that hypertonic saline solution inhalation could cause a low-grade inflammation in airways, and levels of inflammatory markers such as IL-6, TNF-α, and pH in EBC may be a useful noninvasive way to assess and monitor airway inflammation.