Editorials

Condensing Exhaled Breath Into Science

Exhaled breath is a promising specimen for in vivo drug analysis. The analysis of non-volatile drugs (NVDs) in exhaled breath is especially valuable due to the clinical prevalence of NVDs. NVDs transfer from the body to the exhaled air in the form of exhaled breath particles (EBPs). The generation of EBPs involves multiple sites in the respiratory tract and complex mechanisms linked to breathing maneuvers. The exhaled NVDs concentrations typically fall within the range of pg L⁻¹, presenting significant analytical challenges. Breath analysis for NVDs finds utility in drugs of abuse testing and therapeutic drug monitoring, with a growing body of related studies. This review thoroughly describes the origin of NVDs in exhaled breath, and summarizes the characteristics and limitations of current analytical methods for exhaled NVDs, as well as the applications of breath analysis for NVDs, in order to provide helpful guidance for subsequent basic and translational research.

Breath testing has enormous potential in the medical diagnostic field. The underlying complexity and perceived availability of adequate specimens, combined with a lack of knowledge of the metabolic pathways that give rise to compounds that are sources of analytes detectable in breath, has greatly slowed development. These real obstacles have recently been largely overcome in the use of breath testing to identify patients with cystic fibrosis associated Pseudomonas aeruginosa infection and tuberculosis. This review summarizes progress made in the characterization of microbial volatiles produced by major lower respiratory tract bacterial pathogens, and their potential use as diagnostic markers in patient breath testing.