Exhaled breath condensate explained

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. Despite its promises, it has not been proven for screening or diagnosing diseases of the lung and other conditions, yet. 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 not only the composition of the airway lining fluid and alveoli. EBC may also mix with salivary and gastric droplets. In addition, volatile gases arising from the alveoli, lower and upper airway wall as well as oral cavity dissolve into the exhaled water vapour and influence its pH.[3] 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,[4] [5] hydrogen peroxide,[6] proteins, cytokines, eicosanoids,[7] [8] and macromolecules such as mucin, phospholipids and DNA.[9] [10] 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,[11] 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 have been demonstrated to have pepsin (usually localised to the stomach) in their EBC.[12] Patients with COPD and asthma have been demonstrated to have increased levels of reactive oxygen species[13] and histamine after bronchial challenge (Ratnawatti 2008).

The content of exhaled breath condensate, however, is also strongly affected by physiological factors, such as diet,[14] physical exercise[15] [16] [17] and even pregnancy may affect mediator concentrations.[18]

Collection devices

The chemical properties of the collection 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. Disposable exhaled breath condensate collector. This device is placed inside a metal sleeve which has been chilled in a freezer. The collection temperature gradually increases as it is used at room temperature. After use the disposable condensation tube inside is then removed from the external metal sleeve and the sleeve is returned to the freezer. Condensate is extracted from the walls of the condensation tube using a plunger and swept into a fluid pool for analysis.

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. Bikov A, Lazar Z, Schandl K, Antus BM, Losonczy G, Horvath I. Exercise changes volatiles in exhaled breath assessed by an electronic nose. ACTA PHYSIOLOGICA HUNGARICA 98:(3) pp. 321–328. (2011)
  4. 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.
  5. Bikov A, Antus B, Losonczy G, Horváth I. Exhaled breath condensate pH (Chapter 13). In: Horvath I, J C de Jongste (editors). Exhaled biomarkers: Clinical handbook for the respiratory professional. 249 p.Plymouth: European Respiratory Society Journals Ltd., 2010. pp. 173–182. (European Respiratory Society Monograph; 49.)
  6. Gajdocsi R, Bikov A, Antus B, Horvath I, Barnes PJ, Kharitonov SA. Assessment of reproducibility of exhaled hydrogen peroxide concentration and the effect of breathing pattern in healthy subjects. JOURNAL OF AEROSOL MEDICINE AND PULMONARY DRUG DELIVERY 24:(6) pp. 271–275. (2011)
  7. 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
  8. Bikov A, Gajdocsy R, Huszar E, Szili B, Lazar Z, Antus B, Losonczy G, Horvath I. Exercise increases exhaled breath condensate cysteinyl leukotriene concentration in asthmatic patients. JOURNAL OF ASTHMA 47:(9) pp. 1057–1062. (2010)
  9. 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
  10. 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. 1 February 2008;177(3):337–41
  11. Lazar Z, Cervenak L, Orosz M, Galffy G, Komlosi ZI, Bikov A, Losonczy G, Horvath I. Adenosine Triphosphate Concentration of Exhaled Breath Condensate in Asthma. CHEST 138:(3) pp. 536–542. (2010)
  12. 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))
  13. 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. . Nitric Oxide, 8(1), 26–30.
  14. Bikov A, Pako J, Montvai D, Kovacs D, Koller Z, Losonczy G, Horvath I. Exhaled breath condensate pH decreases following oral glucose tolerance test. JOURNAL OF BREATH RESEARCH 9:(4) p. 047112. (2015)
  15. Bikov A, Lazar Z, Schandl K, Antus BM, Losonczy G, Horvath I. Exercise changes volatiles in exhaled breath assessed by an electronic nose. ACTA PHYSIOLOGICA HUNGARICA 98:(3) pp. 321–328. (2011)
  16. Bikov A, Gajdocsy R, Huszar E, Szili B, Lazar Z, Antus B, Losonczy G, Horvath I. Exercise increases exhaled breath condensate cysteinyl leukotriene concentration in asthmatic patients. JOURNAL OF ASTHMA 47:(9) pp. 1057–1062. (2010)
  17. Bikov A, Galffy G, Tamasi L, Bartusek D, Antus B, Losonczy Gy, Horvath I. Exhaled breath condensate pH decreases during exercise-induced bronchoconstriction. RESPIROLOGY 19:(4) pp. 563–569. (2014)
  18. Eszes N, Bikov A, Lazar Z, Bohacs A, Muller V, Stenczer B, Rigo J Jr, Losonczy G, Horvath I, Tamasi L. Changes in exhaled breath condensate pH in healthy and asthmatic pregnant women. ACTA OBSTETRICIA ET GYNECOLOGICA SCANDINAVICA 92:(5) pp. 591–597. (2013)

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