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. 2012 Apr 15;185(8):803-4.
doi: 10.1164/rccm.201109-1702ED.

Exhaled breath condensates: analyzing the expiratory plume

Richard M Effros  1 , Richard Casaburi, Janos Porszasz, Edith M Morales, Virender Rehan
Affiliations

Exhaled breath condensates: analyzing the expiratory plume

Richard M Effros et al. Am J Respir Crit Care Med. .
No abstract available

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Figures

Figure 1.
Figure 1.
Contributions of diffusion and convection to formation of the expiratory plume. Rapid diffusion of water (evaporation) occurs from the fluid lining the surfaces of the airways (e.g., bronchi), the airspaces (e.g., alveoli), and mouth into the expiratory flow. Exhaled water vapor remains in the gas phase until it is cooled and captured as droplets in the condenser. Droplet formation within the lungs is largely confined to the airways, where turbulence is encountered. These droplets contain airway lining fluid and are the source of virtually all of the nonvolatile biomarkers, ions, and dilutional indicators that reach the condensate. They are presumably formed by convective detachment from the surface fluid on the airway surfaces or by expulsion of aqueous films spanning airway openings (perhaps causing audible rales). Because the rate of droplet formation is so miniscule compared with the movement of gases from the lungs, transport of nonvolatile constituents is generally much slower than diffusive transport of volatile molecules. Most of the NH3 and many other gases (e.g., from bacterial metabolism) diffuse into the exhaled stream from the mouth, nose, and upper gastrointestinal tract. High concentrations of these volatile molecules are much more readily maintained at sites (e.g., oral cavity) relatively remote from exchange vessels. Diffusion of respiratory gases occurs primarily between the gas, tissues, and blood in the alveoli, but the site of diffusion of more soluble vapors (such as acetone) is typically greater in the airways.
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