Decreased heart rate variability (HRV) is associated with posttraumatic stress disorder (PTSD) and depression symptoms, but PTSD's effects on the autonomic stress response and the potential influence of HRV biofeedback in stress relaxation training on improving PTSD symptoms are not well understood. The objective of this study was to examine the impact of a predeployment stress inoculation training (PRESTINT) protocol on physiologic measures of HRV in a large sample of the military population randomly assigned to experimental HRV biofeedback-assisted relaxation training versus a control condition. PRESTINT altered the parasympathetic regulation of cardiac activity, with experimental subjects exhibiting greater HRV, that is, less arousal, during a posttraining combat simulation designed to heighten arousal. Autonomic reactivity was also found to be related to PTSD and self-reported use of mental health services. Future PRESTINT training could be appropriate for efficiently teaching self-help skills to reduce the psychological harm following trauma exposure by increasing the capacity for parasympathetically modulated reactions to stress and providing a coping tool (i.e., relaxation method) for use following a stressful situation.
The objective of this pilot study was to design, develop, and evaluate a predeployment stress inoculation training (PRESIT) preventive intervention to enable deploying personnel to cope better with combat-related stressors and mitigate the negative effects of trauma exposure. The PRESIT program consisted of three predeployment training modules: (1) educational materials on combat and operational stress control, (2) coping skills training involving focused and relaxation breathing exercises with biofeedback, and (3) exposure to a video multimedia stressor environment to practice knowledge and skills learned in the first two modules. Heart rate variability assessed the degree to which a subset of participants learned the coping skills. With a cluster randomized design, data from 351 Marines randomized into PRESIT and control groups were collected at predeployment and from 259 of these who responded to surveys on return from deployment. Findings showed that the PRESIT group reduced their physiological arousal through increased respiratory sinus arrhythmia during and after breathing training relative to controls. Logistic regression, corrected for clustering at the platoon level, examined group effects on post-traumatic stress disorder (PTSD) as measured by the Post-traumatic Stress Checklist after controlling for relevant covariates. Results showed that PRESIT protected against PTSD among Marines without baseline mental health problems. Although limited by a small number of participants who screened positive for PTSD, this study supports the benefits of PRESIT as a potential preventive strategy in the U.S. military personnel.
Post-traumatic stress and other problems often occur after combat, deployment, and other military operations. Because techniques such as mindfulness meditation show efficacy in improving mental health, our team developed a mobile application (app) for individuals in the armed forces with subclinical psychological problems as secondary prevention of more significant disease. Based on the Personal Health Intervention Toolkit (PHIT), a mobile app framework for personalized health intervention studies, PHIT for Duty integrates mindfulness-based relaxation, behavioral education in sleep quality and alcohol use, and psychometric and psychophysiological data capture. We evaluated PHIT for Duty in usability and health assessment studies to establish app quality for use in health research. Participants (N = 31) rated usability on a 1 (very hard) to 5 (very easy) scale and also completed the System Usability Scale (SUS) questionnaire (N = 9). Results were (mean ± SD) overall (4.5 ± 0.6), self-report instruments (4.5 ± 0.7), pulse sensor (3.7 ± 1.2), sleep monitor (4.4 ± 0.7), sleep monitor comfort (3.7 ± 1.1), and wrist actigraphy comfort (2.7 ± 0.9). The average SUS score was 85 ± 12, indicating a rank of 95%. A comparison of PHIT-based assessments to traditional paper forms demonstrated a high overall correlation (r = 0.87). These evaluations of usability, health assessment accuracy, physiological sensing, system acceptability, and overall functionality have shown positive results and affirmation for using the PHIT framework and PHIT for Duty application in mobile health research.
Background With the increasing use of mobile devices to access the internet and as the main computing system of apps, there is a growing market for mobile health apps to provide self-care advice. Their effectiveness with regard to diet and fitness tracking, for example, needs to be examined. The majority of American adults fail to meet daily recommendations for healthy behavior. Testing user engagement with an app in a controlled environment can provide insight into what is effective and not effective in an app focused on improving diet and exercise. Objective We developed Rams Have Heart, a mobile app, to support a cardiovascular disease (CVD) intervention course. The app tracks healthy behaviors, including fruit and vegetable consumption and physical activity, throughout the day. This paper aimed to present its functionality and evaluated adherence among the African American college student population. Methods We developed the app using the Personal Health Informatics and Intervention Toolkit, a software framework. Rams Have Heart integrates self-reported health screening with health education, diary tracking, and user feedback modules to acquire data and assess progress. The parent study, conducted at a historically black college and university-designated institution in southeastern United States, consisted of a semester-long intervention administered as an academic course in the fall, for 3 consecutive years. Changes were made after the cohort 1 pilot study, so results only include cohorts 2 and 3, comprising a total of 115 students (n=55 intervention participants and n=54 control participants) aged from 17 to 24 years. Data collected over the study period were transferred using the secure Hypertext Transfer Protocol Secure protocol and stored in a secure Structured Query Language server database accessible only to authorized persons. SAS software was used to analyze the overall app usage and the specific results collected. Results Of the 55 students in the intervention group, 27 (49%) students in cohort 2 and 25 (45%) in cohort 3 used the Rams Have Heart app at least once. Over the course of the fall semester, app participation dropped off gradually until exam week when most students no longer participated. The average fruit and vegetable intake increased slightly, and activity levels decreased over the study period. Conclusions Rams Have Heart was developed to allow daily tracking of fruit and vegetable intake and physical activity to support a CVD risk intervention for a student demographic susceptible to obesity, heart disease, and type 2 diabetes. We conducted an analysis of app usage, function, and user results. Although a mobile app provides privacy and flexibility for user participation in a research study, Rams Have Heart did not improve compliance or user outcomes. Health-oriented research studies relying on apps in support of user goals need further evaluation.
Very little is known about the cardiovascular responses of exercising individuals when exposed to carbon monoxide (CO). Sixteen healthy nonsmoking men aged 18-29 years participated in the study. Using a combination of exposures to CO by breathing from a bag or in an environmental chamber, subjects performed a randomized sequence of brief (5 min) multi-level treadmill and hand-crank exercises on different days at less than 2% carboxyhemoglobin (COHb) and after attaining target levels of 5%, 10%, 15%, and 20% COHb. To assess cardiac function changes we employed noninvasive impedance cardiography (ICG) and three-lead electrocardiograms (ECG). The ICG was used to estimate cardiac output, stroke volume, heart rate, cardiac contractility, and time-to-peak ejection time. The ECG was used to assess myocardial irritability and ischemia, and changes in cardiac rhythm. The results showed that the cardiovascular system compensated for the reduced O2-carrying capacity of the blood by augmenting heart rate, cardiac contractility, and cardiac output for both upper-body and lower-body exercise. While this mechanism served well in submaximal exercise, the enhanced cardiovascular response to exercise was not without physiological costs because it began to fail at moderate levels of CO exposure and exercise. We concluded that young, apparently healthy men can perform submaximal upper and lower-body exercise without overt impairment of cardiovascular function after CO exposures attaining 20% COHb.
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