Metin Yildiz

Analysis of the Mobile Phone Effect on the Heart Rate Variability by Using the Largest Lyapunov Exponent

In this study, the effects of electromagnetic fields (EMFs) emitted by GSM900 based mobile phones (MPs) on the heart rate variability (HRV) were examined by using nonlinear analysis methods. The largest Lyapunov exponent (LLE) calculation was used to evaluate the effect of MP under various real exposure conditions. Sixteen healthy young volunteers were exposed to EMFs emitted by GSM900 based MP at two levels from a very low EMF (MP at stand-by) to a higher EMF (MP at pre-ring handshaking and ringing). A blind experimental protocol was designed and utilized with consideration to the physiological and psychological factors that may affect HRV. The results showed that the LLE values increased slightly with higher EMF produced by MP (P < 0.05). This change indicates that the degree of chaos in the HRV signals increased at higher EMF compared to low level EMF. Consequently, we have concluded that high level EMF changed the complexity of cardiac system behavior, significantly.

Computer based eye-writing system by using EOG

The aim of this study is to suggest a faster method that would also have better accuracy rate in coding eye movements into characters compared to previously developed by EOG visual writing techniques and to develop a system of computer-based applications that would implement this new method. To this end, several experiments were utilized in order to determine the performance of the observed coding method we propose, with reference to these experiments results; a new method encoding 29 letters and 3 commands (spaces, erase, read) by utilizing only 4 directions with two different angles and four different waiting period is proposed. For implementing proposed new technique, a computer based EOG measurement and inference system is developed. The results of trials with this newly developed system indicate that while the accuracy rate of coding into right characters in the first trial of a text comprised of 180 letters is 92.5%, this accuracy rate of the coding reaches to 100% starting from the fourth trial of the technique. Average writing speed of 16.8 words per minute that is measured with this method is the highest rate that has been achieved among EOG-based systems.

Feasibility of heart rate variability analysis with heart sounds

Heart rate variability (HRV) analysis, which is providing information about the autonomic nervous system with noninvasive method, performed with using digitized electrocardiogram records. In this study, whether HRV analysis can be done from heart sounds (which are recorded with electronic stethoscopes) has been investigated. For this purpose, an algorithm has been developed for detecting the consecutive heart time period from simultaneously recorded heart sounds and ECG. Some standard HRV parameters are calculated and compared from the HRV derived from ECG and heart sound signals. The experimental results show that, both HRV parameters derived from the heart sounds while the resting position and the ECG are very close. In conclusion, they can be used in HRV analysis.

The effect of classical Turkish musics on the autonomic nervous system

In this study, the effects of two different forms of classical Turkish music (hüseyni and saba) on the Authonomous Nerves System (ANS) are investigated. During listening these music forms, the electrocardiogram (ECG) and respiration records were made from two seperated subjects groups which are age and gender matched. These records have three periods: first period is before the listening, second is listening and third is after the listening. Heart rate variability (HRV) signal are obtained form record and power spectral densities (PSD) of HRV are estimated. According to the results of calculated parameters, both of two forms of Turkish music is cause significant differences on the very low frequency (VLF) power that is effected by hormonal and thermal control or vasomotor aktivities. The high frequency (HF) power of HRV PSDs is increase at listening the form of saba Turkish music and sympatho-vagal balance (LF/HF ratio) is shifted in dominance of parasympathetic activities.

Analysis of the mobile phone effect on the heart rate variability by the calculation of correlation dimension

In this work, the effect of the electromagnetic radiation generated by mobile phone, on the heart rate variability (HRV) has been investigated using correlation dimension calculation which is a nonlinear analysis method. The 17 volunteer subjects participated to our work and the experiment is designed as three periods and each period have 7 minutes. The electrocardiogram (ECG) signals were recorded from volunteers who are in the sitting position between the base station and mobile phone and mobile phone attached to the right ear of the subject by a bone. The mobile phone is continuously called by another mobile phone at the second period for 9 subjects and at the third period for 8 subjects, randomly. Mobile phone was open and standby condition, at the other periods. The HRV signals were obtained from ECG signals and correlation dimension analysis has been performed. The student-t test was applied to the correlation dimension values calculated from mobile phone calling and standby conditions. The correlation dimension that belongs to mobile phone calling condition is found higher than mobile phone standby condition (p≪0.05). The correlation dimension gives the minimum number of independent variables necessary to generate the system dynamics. The results show that the number of variables managed to the cardiovascular system behavior increase by reason of electromagnetic radiation generated by mobile phone.

The effects of classical and turkish music samples on the Autonomic Nervous System

In this study, 27 young and healthy subjects was listening to the classical and Turkish music samples which are believed to changeable the subjects emotional state. Their effects on Autonomic Nervous System (ANS) are investigated by using the heart rate variability (HRV) analysis which is accepted as a non-invasive indicator of ANS. The electrocardiogram (ECG) and respiration records were made before and during the listening music samples. Heart rate variability (HRV) signals are obtained form records and power spectral densities (PSD) of HRV are estimated. According to the results of calculated parameters, during the listening to classical music samples some statistically significant changes were occurred in sympathetic and parasympathetic activities of ANS. Turkish music samples were not causes significant differences on the ANS related HRV parameters.

Effect of spontaneous saliva swallowing on short-term heart rate variability (HRV) and reliability of HRV analysis

The effects of effortful swallowing and solid meal ingestions on heart rate variability (HRV) have been examined previously. The effects of spontaneous saliva swallowing on short‐term HRV and reliability of HRV analysis have not been studied before. The effect of saliva swallowing on HRV analyses parameters [meanRRI, SDNN (standard deviation of normal‐to‐normal), LF (low frequency), HF (high frequency) powers, LH/HF] and the reliability of LF and HF powers were investigated by frequency, time–frequency and intraclass correlation coefficient (ICC) analyses. Electrocardiogram and swallowing signal that obtained from an electronic stethoscope placed on the necks of subjects were recorded simultaneously from 30 healthy and young volunteers in sitting position during 15 min. Spontaneous swallowing has been shown to significantly alter some HRV parameters (SDNN, LF power and LF/HF ratio). Time‐frequency analysis results showed that the contribution of saliva swallowing to LF (1–58%) and HF (2–42%) powers could change significantly depending on the number of swallowing. The ICC of the LF and HF powers for the successive 5‐min signal segments were found 0·89, 0·92, respectively. These values decreased to 0·73 and 0·90 in the subjects with more swallowing rate. When the analyses were made for 2‐min signal periods, these values decreased to 0·63 and 0·67. We concluded that spontaneous saliva swallowing can change HRV parameters. We have also seen that changes in swallowing rate and use of short signal segments may reduce the reliability of HRV analyses.

A New PC-Based Text Entry System Based on EOG Coding

Some disadvantages of optical eye tracking systems have increased the interest to EOG (Electrooculography) based Human Computer Interaction (HCI). However, text entry attempts using EOG have been slower than expected because the eyes should move several times for entering a character. In order to improve the writing speed and accuracy of EOG based text entry, a new method based on the coding of eye movements has been suggested in this study. In addition, a real time EOG based HCI system has developed to implement the method. In our method all characters have been encoded by single saccades in 8 directions and different dwell time. In order to standardize dwell times and facilitate the coding process, computer assisted voice guidance was used. A number of experiments have been conducted to examine the effectiveness of the proposed method and system. At the end of the fifth trials, an experienced user was able to write at average 13.2 wpm (5 letters = 1 word) with 100% accuracy using the developed system. The results of our experiments have shown that text entry with the eye can be done quickly and efficiently with the proposed method and system.

Issues related to reliability of HRV analysis and effect of spontaneous saliva swallowing on HRV

The aim of this letter is to emphasize some of the most important factors that may affect the reliability of heart rate variability (HRV) analysis and to share the initial findings of our recent study on the effects of spontaneous saliva swallowing on HRV and the reliability of HRV analysis. The reliability of HRV analysis is controversial (1). Despite this, more than 28,000 papers related to HRV have been published in SCI. Some of these have been written on the methodology and usage fields of HRV analyses, while some have been examined possible clinical applications. Comprehensive studies have shown that diminished HRV causes mortality and morbidity, and these studies have increased the clinical importance of HRV analysis. However, a significant number of studies have not considered the factors that could affect the reliability of their studies. It has been shown that short-term HRV changes with many factors such as respiratory parameters, speech, prandial state, surrounding sounds, postural stress or physical activities, and emotional state. The reliability of HRV analysis can be increased by various measures. Signal recording should be performed in a quiet and calm environment in the resting position, and the subjects should not be speaking. Records should be taken 3–4 h after the last meal of the subjects. It will be useful to ensure that subjects do not breathe quickly or slowly during recording; if possible, paced breathing can be used. During our previous studies, we have observed that HRV mostly follows respiratory movements with a small phase difference (2, 3). However, in some signal regions on the tacoAnatol J Cardiol 2017; 17: 493-6 Letters to the Editor

A new coding technique for EOG based writing systems

In this study, a new method, which uses fewer eye movements according to similar systems in character coding, was proposed for eye writing system. Vertical and horizontal electrooculogram (EOG) signals were used for coding the 42 different characters consist of letters, numbers, and punctuation. The efficiency of the method was primarily showed by computer simulations. Afterwards, it was tested with real EOG signals taken from three volunteers. It was seen that, when the same control parameters are used for all volunteers, the character recognition algorithm provides 77% accuracy. If volunteer specific changes are applied at control parameters, the algorithm provides 100% accuracy.