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• Generates synthetic heart interval series of healthy subjects. • Variability of the beat intervals of a healthy subject modeled using a chaotic sequence. • A useful reference to compare diseased subjects. • Provides checks on artefact cleaning procedures. A method based on a heart model is developed to generate synthetic RR interval time series of a healthy subject. The model presented here makes no assumptions about the distribution of RR intervals. The main contribution of this paper is the introduction of variability associated in the RR interval series which arises from changes in the input from parasympathetic, sympathetic input as well as from the response of other components in the cardiovascular control circuitry. This is modelled by a time varying chaotic sequence using the improved logistic map multiplied by a constant parameter. In simulating a measured RR series, its mean heart rate is used and a set of ordinary differential equations solved for different values of this constant parameter. This parameter is chosen when the power present in the low frequency (0.04–0.15) Hz and high frequency (0.15–0.4) Hz spectral range of the measured series show minimal error with that present in the synthetic series. The synthetic series generated is devoid of artefacts and is closer to the cleaned version of the measured series. The complexity assessed using sample entropy indicates errors less than 10% between the two series. This indicates that the chaotic function used to model the variability is a suitable choice to give the complexity of a healthy RR series. The artefact free synthetic RR series of healthy subjects provides a useful reference to compare results from diseased subjects; and to test different artefact cleaning procedures on RR data from healthy subjects [ABSTRACT FROM AUTHOR]

Traumatic injuries can have long-term negative impacts on health, especially psychological health. A biopsychosocial approach is recommended to identify those likely to experience psychosocial stress, however large individual differences exist in stress reactivity and post-injury health that remain unexplored. Therefore, we investigated autonomic nervous system (ANS) stress responses and pre-existing psychosocial vulnerability as contributors to health in individuals who sustained a traffic-related injury. 120 adults with traffic-related injury and 112 non-injury controls underwent an integrative ANS (cardiac and skin conductance) assessment and a health-related assessment at 3–6 weeks post-injury. Propensity score matching based on six pre-injury psychosocial vulnerability factors (age, sex, education, prior mental/physical health, socioeconomic status) guided the definition of high vulnerability (HV) and low vulnerability (LV) injury subgroups, with the LV subgroup having similar propensity scores to non-injury controls. A three-group comparative analysis of ANS responsivity (baseline, reactivity, recovery/rebound) and post-injury health was performed. The HV subgroup exhibited the most negative immediate post-injury mental health profile and less adaptive ANS response patterns, indicating greater stress vulnerability/reactivity. Significant differences were found for psychological health (elevated psychological distress and catastrophizing), but not physical health (injury factors, pain, fatigue, physical wellbeing). HV participants showed sympathetic predominance at resting baseline (lower parasympathetic activity and/or elevated heart rate) compared to the LV and control groups, as well as smaller parasympathetic decrease during a cognitive task compared to controls. Despite preserved capacity for restoring initial homeostasis in both injury subgroups during recovery, there was some indication of blunted post-task sympathetic deactivation (larger sympathetic decrease) and reduced overall ANS adaptability (reduction in total power of heart rate variability spectrum), suggesting relative reduced capacity to face stressors compared to controls. Findings suggest that baseline resting ANS regulation, particularly parasympathetic activity, and pre-injury psychosocial factors are key contributors to individual psycho-biological responses following traumatic injury, and are therefore potential stress vulnerability markers. Post-stress recovery patterns may represent a novel physiological signature for a "biological intrinsic" vulnerability early after the injury. These findings provide direction for improved early identification and management of injured individuals, including innovative preventive interventions that target ANS regulation. • Resting autonomic regulation and pre-injury vulnerability were associated with psychological adjustment to traumatic injury. • Individuals with higher pre-injury vulnerability exhibited less adaptive psycho-biological responses to the injury. • Autonomic recovery patterns suggested a reduced capacity to deal with stressors immediately post-injury. [ABSTRACT FROM AUTHOR]