A special issue: Flow, pressure, volume and time as dependent variables in breath analysis

Traditionally, Journal of Breath Research (JBR) publishes papers that focus on the chemical constituents of exhaled breath. When the journal was launched in 2005, the topics were primarily limited to gas-phase compounds, either as indicators of recent environmental exposures or as endogenous markers of current health state. Over the years, the chemical space of breath analytes has expanded to semi- and non-volatile compounds found in exhaled breath condensate and exhaled breath aerosol, including proteins, fatty acids, cytokines and dissolved inorganics, as well as bacterial and viral particles. Gaining access to this class of biomarkers via non-invasive breath sampling has become a welcomed addition or even replacement to collecting and analyzing blood or urine (Pleil and Wallace 2018a, Pleil et al 2018b)

We have also come to acknowledge that compounds expelled via breath are a mixture originating from molecular, cellular, and tissue processes within the body, either from previously absorbed contaminants, or as products of metabolism and other life-based chemistry. This has engendered a new arena for breath publications that embrace in vitro measurements of chemicals emitted from enteric and infectious bacteria, cancer tissues, and human cell-lines. (Pleil et al 2017). Researchers can now develop specific profiles of chemicals, or sometimes just patterns, of such sources expressed in breath and use this information to recognize different infections and disease states for pre-clinical diagnostics.

In line with the growing field of breath analysis, we are now expanding the JBR repertoire with a new addition: the use of pulmonary function, e.g. changes in flow, pressure, volume and timing of breathing as dependent variables describing outcomes of experimental and observational breath studies. The journal had previously discouraged submissions relating to this topic, as they were perceived to be better suited to physiology or medical journals. We now believe, however, that important breath physics research may be lost to the breath research community in the clutter of more generic journals. By expanding the scope of the journal to include pulmonary function we wish to counteract this dispersion effect and offer JBR as a central platform for all aspects of breath research.

To coincide with this broadening scope, JBR is now developing a special issue entitled 'Pulmonary function in diagnostic breath analysis: interpreting flow, pressure, volume and timing as outcome variables' . We will solicit original research and review articles from researchers who have previously published on this subject, and welcome any submissions from the JBR readership or breath research community in general.

As of now we have no preconceived notions of the extent of this venture into the realm of breathing physics. Some anticipated topics for methods development and pulmonary function assessments are:

• Tracking health of COPD, pneumonia, and asthma patients
• Developing medical ventilator protocols
• Testing responses to artificial atmospheres (submarines, aircraft, spacecraft)
• Assessing stress from breathing gear (firefighters, divers, first-responders to chemical incidents)
• Developing better regulated breathing air supplies (e.g. for laboratory personnel, medical patients, firefighters, fighter pilots and astronauts)
• Evaluating supplied air/mask systems for maintenance personnel (confined space)
• Measuring pulmonary function as response to pressure and oxygen concentration (recreational scuba diving, hyperbaric chambers treatment, submariners community)
• Assessing recovery of COVID-19 and other pulmonary compromised patients

There are likely many more topics regarding the physical measurements of breath to complement the more conventional chemical assessments hitherto published in this journal, and we hope that this special issue will provide inspiration and act as an impetus for future work in this arena.

We encourage the JBR readership to submit articles for this special issue on pulmonary function, and to recruit their colleagues and peers in other breath-related fields to consider contributing to the issue as well. We, the editors, are excited about expanding the role of breath research in JBR to the physics and physiology of measurements as a diagnostic tool and we hope that this special issue will resonate with the community and engender a regular influx of pulmonary function article submissions in future regular issues of the journal.