Heart Rate Variability as a Biomarker for Working Memory Performance and Fatigue Perception

Fatigue is a debilitating condition especially in the emergency response (ER) domain where long work hours and sustained cognitive demands impede job performance. Typical solutions such as pharmacological aids (e.g., caffeine or other stimulants), or user-interface alterations (e.g., multimodal feedback) do not address the root of the problem. This is partly because fatigue is a complex, non-linear phenomenon influenced by lifelong subjective experiences and neurophysiological responses. Personalized and task-specific modes of intervention, beyond pharmacological aids, could improve work conditions and the outcome for all stakeholders. Heart rate variability (HRV) is a commonly used non-invasive diagnostic index of cardiac autonomous regulation. Previous studies have discovered strong links between cardiac processes and a variety of prefrontal neural responses, as well as pointing to HRV as an indicator of cognitive performance level and working memory (WM). The electrocardiogram (ECG) is a commonly used non-invasive diagnostic tool; and ECG data have been used in a variety of medical research, such as biometric human identification and sleep staging. We take data from a fatigue experiment done by our group that investigated the use of transcranial direct current stimulation (tDCS) – a non-invasive brain stimulation technique on mitigating fatigue and improving individual working memory (WM) performance. The study used a repeated measure, counterbalanced Latin square design where participants were randomly grouped under control, sham or anodal conditions. Subjective responses, WM performance, and HRV data were recorded. We hypothesize that: (1) individuals with higher resting-state HRV will exhibit better performance and report lower levels of perceived fatigue; and (2) changes in HRV during tasks will be associated with concurrent, positively related changes in performance and (or) negatively related changes in fatigue perception. This study intends to unveil the relationship between HRV, WM performance, and fatigue perceptions. We will investigate the relevance of resting-state and time-on-task changes in HRV on reflecting fatigue perceptions and task performance during the WM exercise. Ultimately, we aim to provide a fieldable and unobtrusive measurement of fatigue for emergency responders using HRV that will contribute to personalized fatigue countermeasures

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 162, January 1977

This bibliography lists 189 reports, articles, and other documents introduced into the NASA scientific and technical information system in December 1976

Advancing orthostatic hypotension diagnostics

This thesis investigated the diagnostics of orthostatic hypotension (OH). OH is defined as a sustained systolic/diastolic blood pressure (BP) drop larger than 20/10 mmHg within 3 minutes after standing up. OH is common among older adults aged above 65 years (6 – 31%) and geriatric outpatients (22-56%), sometimes accompanied by orthostatic intolerance (dizziness, light-headedness and blurry vision) and associated with poor clinical outcome (cardiovascular diseases, impaired cognitive performance and mortality). Current OH diagnostics is limited due to 1) contradictory evidence on the association between the OH definition and physical functioning and falls; 2) the uncertainty of the clinical value of continuous BP measurements, which may in contrast to intermittent sphygmomanometer measurements reflect the challenge posed to compensation systems and brain exposure to low perfusion pressures; and 3) the lack of assessment of systems compensating for orthostatic BP drops such as baroreflex sensitivity (i.e., heart rate increase in response to a BP drop to stabilize BP), peripheral vasoconstriction (i.e., narrowing of peripheral artery diameter in response to a BP drop to increase peripheral resistance and stabilize BP) and cerebral autoregulation (i.e., dilation of cerebral arterioles in response to a BP drop to keep cerebral blood flow constant). In conclusion, the currently used OH definition was found to be clinically valuable as patients diagnosed according to this definition are at increased risk of impaired physical functioning and falls. BP drop rate and BP recovery derived from continuous BP measurements were found to have added clinical value by their association with clinical outcome and may after confirmation of the results in further studies have to be incorporated in a new OH definition for continuous orthostatic BP measurements to better identify individuals with clinical consequences due to OH. Parameters expressing baroreflex sensitivity, cerebral oxygenation and cerebral autoregulation were by their sensitivity, test-retest reliability and validity in younger and older adults demonstrated to be potentially valuable, supporting further study on the clinical value of these parameters

Wearable and app-based resilience modelling in employees:exploring the possibilities to model psychological resilience using wearable-measured heart rate variability and sleep

Stress has a major impact on both an individual and a societal level. Early recognition of the negative impact of stress or reduced resilience can be used in personalized interventions that enable the user to break the identified pattern through timely feedback, and thus limit the emergence of stress-related problems. The emergence of wearable sensor technology makes it possible to continuously monitor relevant behavioral and physical parameters such as sleep and heart rate variability (HRV). Sleep and HRV have been linked to stress and resilience in population studies, but knowledge on whether these relationships also apply within individuals, which is necessary for the aforementioned personalization, is lacking. This thesis introduces a cyclical conceptual model for resilience and four observational studies that test relationships between sleep, HRV and subjective resilience-related outcomes within participants using different types of data analysis at different timeframes. The relationships from the conceptual model and the related hypotheses are broadly confirmed in these studies. Participants tended to have more favorable subjective stress- and resilience-related outcomes on days with a relatively high resting HRV or long total sleep duration. Also, having a resting HRV that fluctuates relatively little from day to day was related to less stress and somatization. However, the strength of the relationships found was modest. The current findings can therefore not yet be directly implemented to initiate meaningful feedback, but they do provide starting points for future research and take a relevant step towards the possible future development of automated resilience interventions

Annual Highlights of Results from the International Space Station

To date, research on the International Space Station (ISS) has helped answer scientific questions ranging from 'How do fluids flow in space?' to 'What are the origins of the universe?', and the science and technology returns have grown at a steady pace. The on-orbit international crew have been busier than ever performing research and technology development activities for use on Earth and in space. As of October 1, 2016, more than 2000 investigations were conducted across the international partnership resulting in more than 1900 publications in journals, conferences, and other gray literature (such as magazines, DVDs, and patents). This report is intended to provide an overall highlight of research results published from October 1, 2015 to October 1, 2016 from investigations operated on the ISS. These results represent the research of approximately 500 scientists around the world for investigations sponsored by the National Aeronautics and Space Administration (NASA), the Roscosmos State Corporation for Space Activities (Roscosmos), the Japanese Aerospace Exploration Agency (JAXA), the European Space Agency (ESA), and the Canadian Space Agency (CSA). Like a typical laboratory on Earth, the logistics of the ISS allows for many investigations to be carried forward over several ISS crew expeditions, enabling repeated experimentation and data collection important for answering critical research questions. Impacts of these results reach beyond the field of space research into traditional areas of science in multidisciplinary ways

The use of wearable/portable digital sensors in Huntington’s disease: a systematic review

In chronic neurological conditions, wearable/portable devices have potential as innovative tools to detect subtle early disease manifestations and disease fluctuations for the purpose of clinical diagnosis, care and therapeutic development. Huntington’s disease (HD) has a unique combination of motor and non-motor features which, combined with recent and anticipated therapeutic progress, gives great potential for such devices to prove useful. The present work aims to provide a comprehensive account of the use of wearable/portable devices in HD and of what they have contributed so far. We conducted a systematic review searching MEDLINE, Embase, and IEEE Xplore. Thirty references were identified. Our results revealed large variability in the types of sensors used, study design, and the measured outcomes. Digital technologies show considerable promise for therapeutic research and clinical management of HD. However, more studies with standardized devices and harmonized protocols are needed to optimize the potential applicability of wearable/portable devices in HD

Physiological stress reactivity and recovery: Some laboratory results transfer to daily life.

Stress is a prevalent theme in our daily lives and is related to numerous negative health outcomes. Laboratory research has studied the physiological stress response extensively with objective measures such as vagally-mediated heart rate variability (vmHRV). Recently, the vagal tank theory emerged as a promising approach to predicting adaptive vmHRV levels around stressful events. This study aimed to investigate whether the predictions of the vagal tank theory about vmHRV during stress reactivity and recovery translate into naturalistic stressful events in daily life. Sixty-seven students wore an EcgMove 4 sensor for 4 days to measure vmHRV. Through a combination of device-based and self-report assessment, vmHRV data were segmented into before, during, and after stressful events. VmHRV segments were analyzed with multilevel modeling, accounting for physiological and psychological covariates. VmHRV before stressful events predicted more adaptive vmHRV during the event but not vmHRV recovery afterwards. The results therefore partially support the vagal tank theory's predictions with data from daily life and allow recommendations for future studies of real-world stress reactivity and recovery. The value of intraindividual variations in vmHRV as predictors of adaptive stress response is underscored by these findings and could inform future interventions that seek to increase momentary vmHRV

Human Research Program Integrated Research Plan

The Integrated Research Plan (IRP) describes the portfolio of Human Research Program (HRP) research and technology tasks. The IRP is the HRP strategic and tactical plan for research necessary to meet HRP requirements. The need to produce an IRP is established in HRP-47052, Human Research Program - Program Plan, and is under configuration management control of the Human Research Program Control Board (HRPCB). Crew health and performance is critical to successful human exploration beyond low Earth orbit. The Human Research Program (HRP) is essential to enabling extended periods of space exploration because it provides knowledge and tools to mitigate risks to human health and performance. Risks include physiological and behavioral effects from radiation and hypogravity environments, as well as unique challenges in medical support, human factors, and behavioral or psychological factors. The Human Research Program (HRP) delivers human health and performance countermeasures, knowledge, technologies and tools to enable safe, reliable, and productive human space exploration. Without HRP results, NASA will face unknown and unacceptable risks for mission success and post-mission crew health. This Integrated Research Plan (IRP) describes HRP s approach and research activities that are intended to address the needs of human space exploration and serve HRP customers and how they are integrated to provide a risk mitigation tool. The scope of the IRP is limited to the activities that can be conducted with the resources available to the HRP; it does not contain activities that would be performed if additional resources were available. The timescale of human space exploration is envisioned to take many decades. The IRP illustrates the program s research plan through the timescale of early lunar missions of extended duration