Adriana Arza

Inclusion of Respiratory Frequency Information in Heart Rate Variability Analysis for Stress Assessment

Respiratory rate and heart rate variability (HRV) are studied as stress markers in a database of young healthy volunteers subjected to acute emotional stress, induced by a modification of the Trier Social Stress Test. First, instantaneous frequency domain HRV parameters are computed using time-frequency analysis in the classical bands. Then, the respiratory rate is estimated and this information is included in HRV analysis in two ways: 1) redefining the high-frequency (HF) band to be centered at respiratory frequency; 2) excluding from the analysis those instants where respiratory frequency falls within the low-frequency (LF) band. Classical frequency domain HRV indices scarcely show statistical differences during stress. However, when including respiratory frequency information in HRV analysis, the normalized LF power as well as the LF/HF ratio significantly increase during stress (p-value <; 0.05 according to the Wilcoxon test), revealing higher sympathetic dominance. The LF power increases during stress, only being significantly different in a stress anticipation stage, while the HF power decreases during stress, only being significantly different during the stress task demanding attention. Our results support that joint analysis of respiration and HRV obtains a more reliable characterization of autonomic nervous response to stress. In addition, the respiratory rate is observed to be higher and less stable during stress than during relax (p-value <; 0.05 according to the Wilcoxon test) being the most discriminative index for stress stratification (AUC = 88.2%).

Changes in respiration during emotional stress

In this work, we analyze changes in respiration during emotional stress induced by a modification of the Trier Social Stress Test. The following stages in the test were analyzed: the pre-relaxing stage, the story telling stage, the anticipation of stress and the video exposition stage. Respiration signal is recorded during the whole test using a thoracic band. Power spectral density (PSD) of respiration is computed in running windows using a modification of Welch periodogram in which sufficiently peaked spectra are averaged. Then, respiratory frequency (FR) is estimated from the “peaked-conditioned” averaged spectra. Results show that respiratory rate is significantly (p <; 0.05 according to the Friedman test) higher, while a measure of spectral peakness and the percentage of PSD used to compute (FR) is lower during stress stages than during relax. These results suggest that the respiration-related parameters have potential discrimination power for stress level assessment.

Towards an objective measurement of emotional stress

This paper presents preliminary results of an experimental study that aims to find an objective measure of emotional stress by using physiological variables. Biochemical stress markers, psychometrics tests and physiological signals were recorded during two different session to 40 healthy young adults (17 men and 23 women). The first session seeks to measure stress baseline state of each subject and the state of deep relaxation that is achieved by autogenic techniques. The second session seeks to measure the state of stress generated by a memory test and an arithmetic task, based on the Trier Social Stress Test. Psychometrics tests show an increment of 40% of stress level at the second session in comparison with the first session. Cortisol levels in men have a significant increments. Physiological signal show significant response to stress stimulus applied in the second experimental session. It can be seen that face temperature increases during the session due to vasodilation; meanwhile the hand temperature decreases the effect on vasoconstriction.

Evaluation of chronic stress indicators in geriatric and oncologic caregivers: a cross-sectional study

Abstract Caregiving induces chronic stress with physical and psychological impact on informal caregivers health. Therefore, subjective and objective indicators are needed for the early diagnosis of pathologic stress to prevent the risk of developing stress-related diseases in caregivers. Our aim was to assess the self-perceived stress, that is, how and how much the stressor affects the individual, through endocrine, metabolic, and immunologic biomarkers levels in geriatric and oncologic informal caregivers. Informal caregivers and non-caregivers were invited to participate in a cross-sectional study at the Clinic Hospital of Barcelona. Demographic and lifestyle characteristics, self-perceived stress (Perceived Stress Scale, State-Trait Anxiety Inventory and Stress Visual Analogue Scale), and biomarkers (copeptin, glucose, glycated hemoglobin, low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), cholesterol, triglycerides, α-amylase, cortisol, tumor necrosis factor (TNF-α), and Interleukins (IL-6 and IL-10)) were evaluated. Descriptive and non-parametric statistical data analysis were performed. Fifty-six subjects (19 non-caregivers, 17 geriatric caregivers, and 20 oncologic caregivers) participated. Median age (IQR) was 57 years (47–66) and 71.46% were women. Self-perceived stress was higher in oncologic caregivers than geriatric caregivers in all psychometric test analyzed (Wilcoxon Rank Sum test, p value < .05). Glucose concentrations and glycated hemoglobin levels differed statistically among groups (Kruskal–Wallis test (K–W tests), p value < .05), even though the median levels were not clinically relevant. Levels of other biomarkers did not differ significantly (K–W tests, p value > .05). These findings suggest that perceived stress is not homogeneous in the caregivers community and thus these two groups could be differentiated. These results provide the baseline information to initiate social actions addressed to each group of caregivers to increase their wellbeing.

Environmental temperature changes as stress stimulus

This article presents the preliminary results of the stress response in 17 healthy young people under high temperature and humidity as a stressor stimulus. The aim of this study is to determine the variations on stress biomarkers due to prolonged exposure to an environment characterized by high temperature (35 °C) and high relative humidity (45%). The experimental protocol proposed as stress biomarkers recording skin temperature, electrocardiogram, respiratory rate, pulse wave, skin conductance, electromyography, blood samples and saliva to determine: Prolactin, Co-pectina, Glucose, Cortisol and a-amylase. Additionally, psychometric tests and Trail Making Test was applied. The measurement session consisted of seven hours divided into three phases where stress biomarkers are recorded: 1) Ambient Control (2 hours at 20°C and 45% of humidity), habituation to climatic chamber and sensors, 2) Thermal stress (2 hours at 35°C and 45% humidity), 3) Returning to control (2 hours at 20° C and 45% humidity). Preliminary analysis of the results shows that during the second phase of the session changes occur in the levels of a-amylase saliva and blood prolactin. The visual analogue scale is most sensitive among applied test.