Asthma and chronic obstructive pulmonary disease (COPD) are two common inflammatory airway diseases characterized by airway inflammation and mucus hypersecretion. Prediction of the outcome of these diseases may not be performed and the need for non-invasive diagnostic tools capable of identifying inflammation in asthma and COPD becomes therefore obvious. Validation, sensitivity and specificity of most non-invasive methods to detect and monitor inflammatory responses in airways are poor and there is a great need to identify and standardize less invasive, or non-invasive methods for investigation of airway inflammation.

Epithelial lining fluid (ELF) covers the airway surface and contains soluble and insoluble inflammatory cell products and plasma proteins originating and passively transferred from the underlying tissue. Airborne aerosol particles containing ELF saturated with water may be recovered in exhaled air by allowing the air to pass a cold surface, creating exhaled breath condensate (EBC). EBC may then be analysed for various components of interest.

The aims of this thesis were (1) to explore whether a certain profile of inflammatory cell markers in EBC, saliva or serum may be identified in patients with allergic asthma or COPD, (2) to evaluate the efficacy and reproducibility of a measurable marker in EBC using either of the two condensers ECoScreen or RTube and (3) to evaluate the value of chlorine concentrations in EBC as well as reproducibility of assessments of certain compounds in EBC.

Material and methods: Thirty-six patients with asthma, 49 smokers or ex-smokers and 25 healthy volunteers participated in three clinical studies. In addition, efficacy, reproducibility and comparison of the two condensers were studied in an ex vivo set up using aerosols of solutions of saline, myeloperoxidase (MPO) or human neutrophil lipocalin (HNL). Aerosol boluses were transferred by means of a servo ventilator to either of the two condensers. Concentrations of chlorine (presumed to be a marker of mucous secretion) in EBC or saliva were analyzed by means of a sensitive coulometric technique (AOX). The inflammatory cell markers histamine, MPO, HNL, lysozyme, cysteinyl-leukotrienes (CysLT) and eosinophil cationic protein (ECP) were analysed in EBC, saliva and/or serum by means of ELISA, RIA, EIA or immunochemical fluorescence methods, respectively. Lung function tests, including diffusion capacity were measured by standard techniques according to clinical routines.

Results and Conclusions: Chlorine measurements served as the main tool in our tests and intra-assay variability <10% was recorded. However, flow dependency, temperature dependency, substance dependency and concentration dependency characterized yields of EBC. Despite acceptable analytical precision, low concentration levels of inflammation markers, biological variability and occasionally contamination with saliva mean that the feasibility of the EBC method is limited. Despite biological variability, concentrations of chlorine in EBC were significantly higher during than after a mild pollen season, suggesting that chlorine concentrations in EBC are a sensitive marker of allergic airway inflammation. A vast number of confounding factors made interpretations of EBC data obtained from COPD and non-COPD patients difficult and traditional diagnostic tools, such as diffusion capacity (DLCO) and serum lysozyme appeared to best discriminate between COPD and non-COPD.