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Exhaled breath condensate

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Exhaled breath condensate (EBC) is the exhalate from breath, that has been condensed, typically via cooling using a collection device (commonly to 4°C or subzero temperatures using a refrigerating device).[1] EBC reflects changes in the respiratory fluid that lines the airways and is an inexpensive, non-invasive tool that has potential for scientific research, screening or diagnosing diseases of the lung and other conditions. It has long been appreciated that the exhaled breath is saturated by water vapour (e.g. by wind musical instrument players), but using it for studies of the lung was probably first described in the Russian scientific literature.[2]

Overview

Exhaled breath condensate reflects the composition of the airway lining fluid and alveoli. The primary constituents of EBC include:

  1. Aerosolised particles of airway lining fluid collected from the airways induced by airflow, probably by turbulence.
  2. Water vapour condensation produced around the aerosolised particles
  3. Water soluble volatile gases dissolved into the water vapor condensate

As EBC reflects the composition of the airway lining fluid, it contains most molecules found in the airway, but these are probably diluted by water vapour. Thus, these can range from simple ions, e.g. H+ measured as pH [3], hydrogen peroxide, proteins, cytokines, eicosanoids [4], and macromolecules such as mucin, phospholipids and DNA [5][6]. Dilution is an issue that is a problem with all methods of sampling the airway and lungs including sputum collection and bronchoalveolar lavage. Suggestions to allow for dilution include using a denominator such as protein, urea or conductivity, but no single method is universally accepted at present.

Increasing evidence indicates that in disease states EBC contains molecules reflective of that disease or greater concentrations of particular markers. For example, patients with gastroesophageal reflux disease patients have been demonstrated to have pepsin (usually localised to the stomach) in their EBC [7]. Patients with COPD and asthma have been demonstrated to have increased levels of reactive oxygen species [8] and histamine after bronchial challenge (Ratnawatti 2008)

Collection devices

The chemical properties of the collection device will influence device will influence the device and its characteristics. Some devices can contaminate the sample, or react with oxidative markers particularly if containing metals

Examples of devices include:

  1. Simple, custom-made. These include glass tubes cooled by ice, Teflon tubing in ice or in dry-ice or water-cooled glass condensers.
  2. Refrigeration systems. These allow the regulation of the collection temperature usually within a pre-set range.
  3. Cooled metal sleeve device. This uses a cooled metal jacket stored in a freezer which is then used at room temperature and has a plunger to collect condensate from the walls of the device. The collection temperature gradually increases once it is used at room temperature.

Potential applications

EBC has potential uses in combination with exhaled breath analysis. There is significant interest in Exhaled nitric oxide analysis in conjunction with EBC analysis but in addition, the analysis of the breath has many applications. Well known examples include and estimation of the breath alcohol level, but others included non-invasive measurements to estimate blood glucose, and well as using it for diagnosing other systemic and local lung diseases, such as lung cancer.

Footnotes

  1. ^ Liu, J., Conrad, D. H., Chow, S., Tran, V. H., Yates, D. H., & Thomas, P. S. (2007) Collection devices influence the constituents of exhaled breath condensate. Eur Respir J, 30(4), 807-808.
  2. ^ Sidorenko, G. I., E. I. Zborovskii, et al. (1980). "[Surface-active properties of the exhaled air condensate (a new method of studying lung function)]." Ter Arkh 52(3): 65-8
  3. ^ Vaughan J, Ngamtrakulpanit L, Pajewski TN, Turner R, Nguyen TA, Smith A, Urban P, Hom S, Gaston B, Hunt J. Exhaled breath condensate pH is a robust and reproducible assay of airway acidity. Eur Respir J. 2003 Dec;22(6):889-94.
  4. ^ Montuschi P Analysis of exhaled breath condensate in respiratory medicine: methodological aspects and potential clinical applications. Ther Adv Respir Dis. 2007 Oct;1(1):5-23
  5. ^ Jackson AS, Sandrini A, Campbell C, Chow S, Thomas PS, Yates DH. Comparison of Biomarkers in Exhaled Breath Condensate and Bronchoalveolar Lavage. Am. J. Respir. Crit. Care Med. 2007; 175(3): 222 - 227
  6. ^ Carpagnano GE, Foschino-Barbaro MP, Spanevello A, Resta O, Carpagnano F, Mulé G, Pinto R, Tommasi S, Paradiso A. 3p microsatellite signature in exhaled breath condensate and tumor tissue of patients with lung cancer. Am J Respir Crit Care Med. 2008 Feb 1;177(3):337-41
  7. ^ Krishnan, A., Chow, S., Thomas, P., Malouf, M., Glanville, A., & Yates, D. (2007). Exhaled breath condensate pepsin: a new noninvasive marker of GERD after lung transplantation. J Heart Lung Transplant, 26((2 Suppl. 1))
  8. ^ Massimo, C., Alberto, P., Romano, C., Rossella, A., Matteo, G., Maria, V. V., et al. (2003). Nitrate in exhaled breath condensate of patients with different airway diseases. doi:10.1016/S1089-8603(02)00128-3. Nitric Oxide, 8(1), 26-30.
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