Measurement of Dermal Ammonia Emission Using a Passive Flux Sampler and Its Association with Autonomic Nervous System...

Medical workers are frequently exposed to high-stress environments, highlighting the need for non-invasive stress monitoring strategies based on autonomic nervous system activity. Ammonia emitted from the human skin surface has been reported to increase under physical and psychological stress; however, its relationship with autonomic nervous system (ANS) dynamics remains unclear. In this study, we performed simultaneous, time-resolved measurements of dermal ammonia emission and heart rate variability (HRV) in 11 medical workers during 3 h of routine work. Dermal ammonia emission flux was continuously monitored using a passive flux sampler (PFS) coupled with ion chromatography, while autonomic nervous system activity was assessed by Holter electrocardiography. The temporal profiles of ammonia emission were analyzed in relation to HRV indices, including high frequency (HF) and the low-frequency-to-high-frequency ratio (LF/HF). Dermal ammonia emission increased under conditions characterized by lower HF and/or higher LF/HF, whereas elevated HF was associated with reduced ammonia emission (r = -0.47, p < 0.001). Furthermore, temporal fluctuations in ammonia emission were associated with sympathetic-parasympathetic switching. These findings suggest that dermal ammonia emission may be associated with HRV-related physiological responses under real-world working conditions and may have potential as a non-invasive indicator for stress-related physiological monitoring.