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Background: The multitude of metabolites generated by physiological processes in the body can serve as valuable biomarkers for many clinical purposes. They can provide a window into relevant metabolic pathways for health and disease, as well as be candidate therapeutic targets. A subset of these metabolites generated in the human body are volatile, known as volatile organic compounds (VOCs), which can be detected in exhaled breath. These can diffuse from their point of origin throughout the body into the bloodstream and exchange into the air in the lungs. For this reason, breath VOC analysis has become a focus of biomedical research hoping to translate new useful biomarkers by taking advantage of the non-invasive nature of breath sampling, as well as the rapid rate of collection over short periods of time that can occur. Despite the promise of breath analysis as an additional platform for metabolomic analysis, no VOC breath biomarkers have successfully been implemented into a clinical setting as of the time of this review. Aim of review: This review aims to summarize the progress made to address the major methodological challenges, including standardization, that have historically limited the translation of breath VOC biomarkers into the clinic. We highlight what steps can be taken to improve these issues within new and ongoing breath research to promote the successful development of the VOCs in breath as a robust source of candidate biomarkers. We also highlight key recent papers across select fields, critically reviewing the progress made in the past few years to advance breath research. Key scientific concepts of review: VOCs are a set of metabolites that can be sampled in exhaled breath to act as advantageous biomarkers in a variety of clinical contexts. [ABSTRACT FROM AUTHOR]

Breath composition analysis is a fast and non-invasive alternative to commonly used methods of detecting lung cancer, such as biopsy. One issue in the study of breath composition is the availability of appropriate sampling and sample-preparation methods that are able to fully capture the gas and droplet phases of exhaled breath. In this article, we detail the application of a filter-incorporated needle-trap device (NTD) to capture gaseous compounds and droplets in breath samples. In addition, a thin-film microextraction method was also employed to conduct extractions from only the gas phase. In comparing the NTD (total concentration) and TFME (free concentration) results, it is possible to obtain a more comprehensive view of the sample, as this approach captures both the free and droplet-bound concentrations, which can in turn provide a better characterization of the cancer. Furthermore, the developed devices were applied for the on-site sampling of lung cancer patients. The complete interpretation of the results and their relationship to the state of the disease and patient health status requires a large cohort of patients and considerable medical expertise; therefore, this study focuses on method development and the application of the proposed device for fast and sensitive on-site detection of biomarkers in patients.

The analysis of exhaled breath has attracted considerable interest for use in disease diagnosis and for monitoring treatments. Mass spectrometry (MS)-based approaches have been proven to be powerful analytical tools for breath analysis in clinical applications such as disease research, diagnosis, and monitoring. This review highlights MS methodologies as potential clinical tools in diagnosing human diseases. Different breath sampling methods and MS methods for breath analysis are reviewed, emphasizing their features, advantages, and limitations. Breath biomarkers from different diseases are summarized, describing their specificity, sensitivity, and drawbacks. The future perspectives and challenges on further development of MS-based breath diagnostics are discussed. [Display omitted] • Recent advances in breath analysis by mass spectrometry are reviewed. • Clinical applications of breath diagnostics are summarized. • Challenges of breath biomarkers for disease diagnosis are highlighted. • Future perspectives on breath diagnostics in clinical applications are discussed. [ABSTRACT FROM AUTHOR]

Assessment and treatment of postoperative pain can be challenging as objective examination techniques to detect and quantify pain are lacking. We aimed to investigate changes of exhaled volatile organic compounds (VOCs) in patients with postoperative pain before and after treatment with opioid analgesics. In an observational study in 20 postoperative patients, we monitored for postoperative pain, hemodynamic parameters, and catecholamines before and during treatment. VOCs in the patients were determined by direct real-time proton transfer reaction time-of-flight mass spectrometry prior (0 min) and after piritramide application (15 min as well as 30 min). Cardiovascular variables changed and norepinephrine levels decreased during treatment. The VOCs acetonitrile (p = 0.002), benzopyran (p = 0.004), benzene (p < 0.001), hexenal (p = < 0.001), 1-butanethiol (p = 0.004), methanethiol (p < 0.001), ethanol (p = 0.003), and propanol (p = < 0.001) changed significantly over time. Patients with Numeric Rating Scale (NRS) < 4 showed a significantly lower concentration of hexenal compared to patients with NRS > 4 at the time points 15 min (45.0 vs. 385.3 ncps, p = 0.047) and 30 min (38.3 vs. 334.6 ncps, p = 0.039). Breath analysis can provide additional information for noninvasive monitoring for analgesic treatment in postoperative patients.

Breath-composition analysis is a well-established, non-invasive method for early disease diagnosis and investigating exposure history. However, this analytical approach is hampered by the aerosol nature of breath samples and/or low concentrations of volatile organic compounds. Conventionally, two separate methods have been applied to study gas phase and breath droplets, although these approaches are expensive and time-consuming. To address this issue, for the first time a needle-trap device packed with Carboxen, which served as a sorbent for the extraction of volatile analytes from the gas-phase, and electrospun polyacrylonitrile filter, which used to capture breath aerosol was applied to breath characterization. The performance of the developed device was subsequently compared to that of Carboxen-loaded thin-film microextraction, which was employed for the first time to extract free gas-phase components. Both methods were optimized, validated, and applied for the screening of breath samples obtained from volunteers. Obtained figures of merits are as follows: limits of detection (0.01–0.2 ng mL−1), recovery (81–108%) and repeatability (<13%). To investigate the effect of droplets, breath samples acquired with and without a face mask were compared. While both methods yielded similar results for the breath samples obtained with the mask, the needle-trap device was able to provide higher concentrations of volatile organic compounds for the samples acquired without a mask due to its enhanced ability to trap droplets. Additionally, tests were also conducted to investigate breath composition after accidental exposure to chemicals. The results of these tests revealed that polar compounds tended to partition to breath droplets and were eliminated from the body more quickly, while non-polar compounds tended to remain in the gas phase and were eliminated at a slower rate. [Display omitted] • A thermally resistant porous filter was prepared from electrospun polyacrylonitrile. • The developed filter and Carboxen particles were packed in the needle-trap device. • Filter-incorporated needle-trap device was applied for study of breath aerosol. • Breath vapor was investigated with Carboxen embedded thin-film microextraction. • The combined data from both methods can be used for comprehensive breath monitoring. [ABSTRACT FROM AUTHOR]

Assessment and treatment of postoperative pain can be challenging as objective examination techniques to detect and quantify pain are lacking. We aimed to investigate changes of exhaled volatile organic compounds (VOCs) in patients with postoperative pain before and after treatment with opioid analgesics. In an observational study in 20 postoperative patients, we monitored for postoperative pain, hemodynamic parameters, and catecholamines before and during treatment. VOCs in the patients were determined by direct real-time proton transfer reaction time-of-flight mass spectrometry prior (0 min) and after piritramide application (15 min as well as 30 min). Cardiovascular variables changed and norepinephrine levels decreased during treatment. The VOCs acetonitrile (<0.001), acetaldehyde (p = 0.002), benzopyran (p = 0.004), benzene (p < 0.001), hexenal (p = < 0.001), 1-butanethiol (p = 0.004), methanethiol (p < 0.001), ethanol (p = 0.003), and propanol (p = < 0.001) changed significantly over time. Patients with Numeric Rating Scale (NRS) < 4 showed a significantly lower concentration of hexenal compared to patients with NRS > 4 at the time points 15 min (45.0 vs. 385.3 ncps, p = 0.047) and 30 min (38.3 vs. 334.6 ncps, p = 0.039). Breath analysis can provide additional information for noninvasive monitoring for analgesic treatment in postoperative patients. [ABSTRACT FROM AUTHOR]