Browsing UA Faculty Publications by Publisher "PHM SOCIETY"
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Dynamic Behavior of Cortisol and Cortisol Metabolites in Human Eccrine SweatThe simultaneous measurement of cortisol with its downstream metabolites in human eccrine sweat is a sensitive approach to capture minute-to-minute stress responses. This study investigates exercise stress induced time dependent dynamic changes in cortisol, cortisone and downstream inactive cortisol metabolites in human eccrine sweat using a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Cortisol and metabolite production (change in concentration over time) was measured in sweat at different time points during an administered exercise stress session with four healthy volunteers. Biomarker production plots were found to be highly individualized and sensitive to stress interventions such as exercise, and corresponded with stress response measures such as increases in heart rate. The LC-MS/MS method yielded baseline resolution between cortisol and cortisol metabolites with lower levels of detection and quantitation for each compound below 1 part-per-billion (ppb). Cortisol and cortisol metabolites were found at concentrations ranging from 1 – 25 ppb in human eccrine sweat. They were also found to be stable in sweat with respect to temperature (37 C for up to 5 hours), pH (3-9) and freeze/thaw cycles (up to 4) This indicates that changes in these biomarker concentrations and their rate of production are due to stress-related physiological enzyme activation, rather than passive degradation in sweat. The physiological status of enzyme activation is thus captured and preserved in human eccrine sweat samples. This is advantageous for the development of wearable devices and methodologies which can assess human health, stress, wellbeing and performance.
A Paradigm Shift from Telemedicine to Autonomous Human Health and Performance for Long-Duration Space MissionsThis paper discusses a Prognostics and Health Management [PHM]-based approach to implementing Human Health & Performance [HH&P] technologies. Targeted specifically are NASA's "Autonomous Medical Decision" and "Integrated Biomedical Informatics" of "Human Health, Life Support, and Habitation Systems" in Technology Area 06 [TA 06] of NASA's integrated technology roadmap [April 2012]. The proposed PHM-based implementation is to bridge PHM, an engineering discipline, to the HH&P technology domain to mitigate space travel risks by focusing on efforts to reduce countermeasure mass and volume, and drive down risks to an acceptable level. NASA's Autonomous Medical Decision technology is based on wireless handheld devices and is a result of a necessary paradigm shift from telemedicine to HH&P autonomy. The Integrated Biomedical Informatics technology is based on Crew Electronic Health Records [CEHR], equipped with a predictive diagnostics capability developed for use by crew members rather than by healthcare professionals. This paper further explores the proposed PHM-based solutions for crew health maintenance in terms of predictive diagnostics to provide early and actionable real-time warnings to each crew member about health-related risks and impending health problems that otherwise might go undetected. The paper also discusses the paradigm's hypothesis and its innovation methodology, as implemented with computed biomarkers. The suggested paradigm is to be validated on the International Space Station [ISS] to ensure that crew autonomy in terms of the inherent predictive capability and two-fault-tolerance of the methodology become the dominant design drivers in sustaining crew health and performance.