Breath Analysis

Exhaled breath constitutes an attractive specimen for forensic and medical investigations. Compared to alternative methods, exhaled breath is always readily accessible, and sampling is both convenient for the donor and non-invasive in nature. Exhaled breath may contain as many detectable components as blood or urine. There are already several FDA approved breath-related tests, but for volatile compounds.

Exhaled breath contains both volatile and non-volatile compounds. The part that contains the non-volatile components is present in the form of aerosol particles. Particles of sizes about 1 μm in diameter, most of them <1 μm in diameter, are always present in human breath. These particles are formed during inhalation, when the small airways re-open and the lining fluid bursts. The particles consist of surfactant, a liquid that is secreted in the distal airways and is crucial for lung function. The exact surfactant composition is functionally important and complex, and consists of lipids, mainly phospholipids, and proteins.

Both the proteins and the lipids are considered important for mechanical and protective functions. Both components may be affected by disease. Thus, surfactant is an interesting source of potential biomarkers.

In 2010, the detection of amphetamine in exhaled breath at about 24 hours after intake was reported. This initiated a new set of work that has explored drug breath testing further. The potential for this new drug testing technology was illustrated by a study of illicit drug users recovering from acute intoxication. Actual drug intake was determined on the basis of self-report, plasma and urine analysis. The results demonstrated that all studied drug substances were detected in the collected exhaled breath samples at the time they were clinically recovered.

Simple sampling of aerosol particles carrying non-volotailes in breath

• Aerosol particles from the airway lining fluid carry non-volatiles from distal parts of the lung.
• The airway lining fluid is composed of lipids and proteins.
• DPPC, PC16:0/16:0 dipalmitoylphosphatidylcholine is a characteristic component of surfactant.
• The aerosol particles are trapped in the three collectors of the BE sampling device by impaction.
• The amount of DPPC is correlated to the mass of captured particles.
• Particles from 12 normal breaths this is enough material to perform the analysis of drugs.
• The actual volume of air is not critical to measure as it is not correlated to the amount of particles.
• For diagnosis, exhaled breath offers a unique possibility of non-invasive collection of material from the airways.
• Being non-invasive, exhaled breath collection can be easily performed on large groups of healthy individuals and respiratory patients, thus providing enough power for case control omics studies designed for discovery of new biomarker candidates.
• Exhaled breath sampling is well suited for repeated sampling, opening up for unbiased hypothesis-generating longitudinal studies in the respiratory research, as well as follow-up targeted studies.

Text by Prof. Olof Beck, Karolinska Institute