Exhaled Breath Condensates: Analyzing the Expiratory Plume
Year: 2012
Type: article
Abstract: The mixture of gases and droplets released during exhalation can be hydrodynamically designated as a "plume."Traditionally, pulmonologists focused on respiratory gases in these plumes, but recent identification of biomarkers in exhaled breath condensates (EBCs) has initiated vigorous efforts to harness this simple, noninvasive approach for diagnostic purposes (.700 citations in PubMed since 2000).A typical condenser removes about half of the approximately 45 ml of liquid water that can theoretically be extracted from each liter of saturated exhaled air.Nearly all of this water evaporates from lung surfaces, but approximately 1/10,000 of the condensate (w4.5 nl) represents droplets released from the airway lining fluid (ALF).The assumption that these droplets are released from airways seems justified because alveolar convection is probably negligible and oral contributions can be minimized.ALF droplets can be generated by detachment from airways or rupture of bubbles from previously occluded airways (1), perhaps associated with audible rales.Passage of exhaled air through the mouth at a site near the condenser makes it difficult to avoid contamination of EBC with salivary fluid.To ensure that saliva represents less than 10% of ALF volume, less than 10 nl of saliva should be collected in each milliliter of EBC, a daunting requirement.However, this was successfully accomplished in 36 of 40 samples when the mouthpiece was separated from the condenser, as judged by a sufficiently sensitive amylase assay (2).Nonvolatile biomarkers (e.g., cytokines, ions, and urea) found in EBCs are exclusively derived from ALF droplets (Figure 1) (3-8).Dilution (D) of ALF by water vapor is generally quite variable, but D can be estimated with nonvolatile "dilutional" standard indicators (S), selected to have similar concentrations in ALF and plasma, for example, urea, cations, or conductivity following lyophilization:Lyophilization is used to extract water and volatiles (e.g., NH 3 and CO 2 ) from ice at temperatures below 250 8 C, and should not be confused with centrifugal evaporation at warmer temperatures, which may denature proteins.The EBC samples can be concentrated by reconstituting the dried samples in smaller volumes of pure water.D must be determined before conclusions
Language: English
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2123362038