Exhaled breath condensate
Encyclopedia
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). 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.
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, hydrogen peroxide, proteins, cytokines, eicosanoids, and macromolecules such as mucin, phospholipids and DNA. 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. Patients with COPD and asthma
have been demonstrated to have increased levels of reactive oxygen species and histamine after bronchial challenge (Ratnawatti 2008)
Examples of devices include:
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.
Overview
Exhaled breath condensate reflects the composition of the airway lining fluid and alveoli. The primary constituents of EBC include:- Aerosolised particles of airway lining fluid collected from the airways induced by airflow, probably by turbulence.
- Water vapour condensation produced around the aerosolised particles
- 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, hydrogen peroxide, proteins, cytokines, eicosanoids, and macromolecules such as mucin, phospholipids and DNA. 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
Pepsin
Pepsin is an enzyme whose precursor form is released by the chief cells in the stomach and that degrades food proteins into peptides. It was discovered in 1836 by Theodor Schwann who also coined its name from the Greek word pepsis, meaning digestion...
(usually localised to the stomach) in their EBC. Patients with COPD and asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
have been demonstrated to have increased levels of reactive oxygen species and histamine after bronchial challenge (Ratnawatti 2008)
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 metalsExamples of devices include:
- Simple, custom-made. These include glass tubes cooled by ice, Teflon tubing in ice or in dry-ice or water-cooled glass condensers.
- Refrigeration systems. These allow the regulation of the collection temperature usually within a pre-set range.
- 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 oxideExhaled nitric oxide
In medicine, exhaled nitric oxide can be measured in a breath test for asthma or other conditions characterized by airway inflammation. Nitric oxide is a gaseous molecule produced by certain cell types in an inflammatory response. The fraction of exhaled NO is a promising biomarker for the...
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.