Exhaled particles and their role in clinical airway research

The standard method to examine the lung and understand the complex processes taking place in this organ is by bronchoscopy. A method that is less stressful for patients would be beneficial under many aspects. In the alveolar lining fluid deep down in the lung, tiny particles are generated and exhaled with each breath – and these can be collected non-invasively. They are a rich source of information for elucidating pulmonary function, structure, and metabolic processes.

After exhaled particles have been collected and separated, they allow a fingerprint of the biochemical composition of the lung mucosal fluid to be generated, for example to monitor pulmonary drug levels. Exhaled particles also provide interesting physical information about the origin and location of an airway occlusion. Furthermore, comprehensive analysis of respiratory particle emissions can help determine the structure of the airways.


"Exhaled Particle Size Index"

What is special at Fraunhofer ITEM: the particles can be measured during every single breath and, through the ratio of large vs. small particles deposited, this can enable insights into airway dimensions. Fraunhofer ITEM researchers are currently working to establish the "Exhaled Particle Size Index" for this purpose. Collected exhaled particles could play a key role in experimental medicine in the future, for example for biomarker analyses.


Potential of exhaled particle analyses

  • Insights into the function of the lung, e.g. superspreading
  • Insights into airway dimensions
  • Biochemical analyses of alveolar lining fluid
  • Monitoring of pulmonary drug levels
  • Noninvasive pathogen diagnosis using genomic analyses

Exhaled particles: "We get deep insights into the lung – non-invasively!"

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Exhaled particles are very small and provide a fingerprint of the epithelial lining fluid. We have developed a technique by which we can determine the deposition of exhaled particles with every single breath. 

Exhaled particles are an intriguing method with broad potential for non-invasive monitoring of the lung.


Schwarz K, Holz O, Hohlfeld JM, Exhaled particles. In: Beauchamp J, Davis C, Pleil J (eds.) Breathborne Biomarkers and the Human Volatilome. Elsevier, Amsterdam. 2020, 121-133.

Schwarz K, Biller H, Windt H, Koch W, Hohlfeld JM. Characterization of exhaled particles from the human lungs in airway obstruction. J Aerosol Med Pulm Drug Deliv. 2015 Feb; 28 (1): 52-8.

Haslbeck K, Schwarz K, Hohlfeld JM, Seume JR, Koch W. Submicron droplet formation in the human lung. J Aerosol Sci. 2010; 41: 429-38.

Schwarz K, Biller H, Windt H, Koch W, Hohlfeld JM. Characterization of exhaled particles from the healthy human lung – a systematic analysis in relation to pulmonary function variables. J Aerosol Med Pulm Drug Deliv. 2010 Dec; 23 (6): 371-9.


Jens Hohlfeld

Contact Press / Media

Prof. Dr. Jens Hohlfeld

Division Director of Airway Research

Phone +49 511 5350-8101