%0 Journal Article
%T Cardiorespiratory Dynamic Response to Mental Stress: A Multivariate Time-Frequency Analysis
%A Devy Widjaja
%A Michele Orini
%A Elke Vlemincx
%A Sabine Van Huffel
%J Computational and Mathematical Methods in Medicine
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/451857
%X Mental stress is a growing problem in our society. In order to deal with this, it is important to understand the underlying stress mechanisms. In this study, we aim to determine how the cardiorespiratory interactions are affected by mental arithmetic stress and attention. We conduct cross time-frequency (TF) analyses to assess the cardiorespiratory coupling. In addition, we introduce partial TF spectra to separate variations in the RR interval series that are linearly related to respiration from RR interval variations (RRV) that are not related to respiration. The performance of partial spectra is evaluated in two simulation studies. Time-varying parameters, such as instantaneous powers and frequencies, are derived from the computed spectra. Statistical analysis is carried out continuously in time to evaluate the dynamic response to mental stress and attention. The results show an increased heart and respiratory rate during stress and attention, compared to a resting condition. Also a fast reduction in vagal activity is noted. The partial TF analysis reveals a faster reduction of RRV power related to (3£¿s) than unrelated to (30£¿s) respiration, demonstrating that the autonomic response to mental stress is driven by mechanisms characterized by different temporal scales. 1. Introduction Stress research has gained growing interest in the last decades. Results from the European Working Conditions Survey in 2000 suggested that 28% of all work-related health problems can be attributed to stress. Work absence associated with stress not only brings along highcosts; for example, in The Netherlands, they estimate a cost of 3 billion ? per year [1], but it is also linked with serious health problems such as cardiovascular diseases [2, 3] and musculoskeletal disorders [1, 4, 5]. It is therefore important to identify the mechanisms underlying stress, such as physiological mechanisms. The autonomic nervous system (ANS) dynamically coordinates, among others, cardiovascular variables (such as heart rate and contractility, blood pressure, and peripheral resistance), respiration, and complex interactions between them. The impact of stress on the cardiovascular system has been investigated extensively via the variability of the RR interval variation (RRV) series [6¨C10]. RRV analysis is widely used to assess the functioning of the ANS. Starting from the RR interval series, several RRV indices that quantify the activity of the ANS have been proposed [11]. In the power spectrum of RRV, a low-frequency (LF) band (0.04¨C0.15£¿Hz) and a high-frequency (HF) band (0.15¨C0.40£¿Hz) are
%U http://www.hindawi.com/journals/cmmm/2013/451857/