Spectral Analysis of HRV in the Assessment of Autonomic Function on Normal Subject Noor Aimie-Salleh Department of Biomedical Instrumentation and Signal Processing, Universiti Teknologi Malaysia, Johor Bahru, Johor aimie@biomedical.utm.my MB Malarvili Department of Biomedical Instrumentation and Signal Processing, Universiti Teknologi Malaysia, Johor Bahru, Johor malarvili@biomedical.utm.my Abstract—Heart rate variability (HRV) has been proposed as a diagnostic tool in assessing autonomic function. This paper investigates HRV response of healthy subject during active postural test (APT) and cold pressor test (CPT) using AR spectral analysis. Electrocardiograph (ECG) was recorded from 30 young adults; 19 females and 11 males with age ranging from 20-30 years. Autoregressive (AR) estimated by Burg was then used to compute the power spectral density (PSD). LFnu, HFnu and LF/HF ratio show significant difference (p<0.05) comparing supine and stand for APT and supine and hand immersion in cold water for CPT. As a conclusion, the HRV response shows predominance of the parasympathetic during supine position and sympathetic predominance during standing and hand immersion in cold water. Keywords-component; Autoregressive; Burg; Cold Pressor Test; Active Postural Test. I. INTRODUCTION HRV is defined as the variation over time of the period between consecutive heartbeats. HRV reflects the ability of the heart to detect and respond to unpredictable changing conditions. HRV is very significant noninvasive tool in revealing and understanding the status of the autonomic nervous system. It also serves as a powerful and dynamic tool in examining the interaction between the sympathetic and parasympathetic nervous systems or also called as sympathetic-parasympathetic autonomic balance [1-2]. The sympathetic and parasympathetic autonomic activities modulate the heart rate interval which is known as R-R interval in the electrocardiogram (ECG), at separate frequencies. In modulation frequency of the heart rate, sympathetic activity falls within low frequency range (0.04–0.15 Hz) while parasympathetic activity is associated with the higher frequency range (0.15–0.4 Hz). The difference in frequency ranges allows HRV analysis to split the sympathetic and parasympathetic contributions in the observed condition [3]. However, this autonomic balance is difficult to be assessed directly. Therefore, in order to diagnose autonomic functions or specifically autonomic dysfunction, the autonomic function test (AFT) has been suggested so that observation can be carried out to identify the HRV response. AFT is a physiological activity or stimuli applied to the patient to get their physiological response such as HRV upon the internal or external changes. AFT plays an essential role in assessing the operational function of autonomic nervous system specifically in evaluating and diagnosing autonomic dysfunction. Common AFT methods in use include the valsalva maneuver, head up tilt table, deep breathing, cold pressor and various active postural changes. AFT is capable of displaying abnormal results even before the clinical symptoms are present. Early detection of autonomic failure is important in order to suggest suitable treatment to the patient at the earliest possible time [4]. In Malaysia studies currently undertaken in the area of autonomic functioning and AFT are few and still in its early stages [5-6]. Thus there is a need for more researches in this area in Malaysia. This paper presents a preliminary study in determining the HRV response during active postural test (APT) and cold pressor test (CPT). The spectral analyses involve employment of autoregressive method. II. METHOD A. Experimental setup Electrocardiograph (ECG) was recorded from healthy subject with no history of cardiovascular or neurological diseases, non-smokers, and not receiving any medication. This study investigates 30 young adults; 19 females and 11 males with age ranging from 20-30 years. The subject was initially asked to rest quietly in the supine position for at least 10 minutes [7]. For active postural test, ECG was then recorded at a sampling frequency of 600 Hz for 5 minutes [8-9] during supine position. After the 5 minutes recording, subjects were instructed to stand upright and another 5 minutes ECG was recorded in the standing position. The cold pressor test was done by first measuring the baseline ECG measurements for 5 minutes. Subsequently, the subject were instructed to immerse his/her left hand [10] to the wrist level into a 0-5°C water bath for a period of 3 minutes, followed by removal of the hand from the water bath, dried and continuation of recording for another 5 minutes [11] 263 2012 International Conference on Biomedical Engineering (ICoBE),27-28 February 2012,Penang 978-1-4577-1991-2/12/$26.00 ©2011 IEEE