Exhaled Breath Condensate

Abstract

Sampling the lining fluid of the lower respiratory tract has traditionally been done via bronchoalveolar lavage (BAL) and sputum collection. These methods are successful in providing helpful research and clinical information, but BAL is invasive and not well standardized, and the intrusion into the respiratory tract may alter the results. Sputum collection is noninvasive and widely used but difficult to process and produces varied results. Exhaled breath condensate (EBC) is a noninvasive and simple method thought to sample the lower respiratory tract. EBC is a process by which the breath passes through a cooling unit and by condensation (liquefied or frozen), a sample is collected for study. This modality for studying the pulmonary system originated in Russia and recently has captured the interest of many investigators. The lining of the lower respiratory tract contains volatile and nonvolatile substances, many of which have been found in EBC. The measurement of these substances has been found to differ among disease states. Quantifying the levels of these substances in EBC has been difficult because the commercially available kits used to measure these substances may not be sensitive enough for the lower concentrations found in EBC compared with the levels found in BAL or other body fluids. Standard values from normal subjects have yet to be established for comparison with disease states. In addition, sample collecting and establishing conventions to normalize and quantify results have yet to be standardized.