To investigate the effect of increasing mental loading on the change of heart rate variability

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To investigate the effect of increasing mental loading on the change of heart rate variability

 

Author: Yu, Kin-ho Daniel
Title: To investigate the effect of increasing mental loading on the change of heart rate variability
Degree: M.Sc.
Year: 2009
Subject: Hong Kong Polytechnic University -- Dissertations.
Heart beat -- Measurement.
Mental fatigue -- Physiological aspects.
Department: School of Nursing
Pages: 91 p. : ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2301883
URI: http://theses.lib.polyu.edu.hk/handle/200/5070
Abstract: Background: Heart rate variability (HRV) is a useful tool to study cardiac autonomic activity. HRV has been found to relate to various medical conditions, physical and mental stress. The measurement of HRV is a reliable and non invasive tool to monitor the condition of human body. Response to mental stress can be culture specific. A large number of studies on HRV and mental stress including arithmetic stress and speech presentation have been undertaken in the West but not in Asia. Therefore, it is worthwhile to perform such a study in Hong Kong, since the problem of stress within this community has been raised in recent years. Objectives: the objectives were 1) to measure the change of different parameters of HRV when normotensive people are placed under mental stress, 2) to measure the prediction power of parameters of HRV on mental stress, and 3) to investigate the effect of personality on the response of HRV to mental stress. Design: A one group pretest and posttest study was conducted. 24 healthy males and females who were aged between 18 and 25 were recruited to take part in this study. They underwent a mental stimulation process by doing mathematical calculation for 10 minutes and post stress resting for 15 minutes with measurement of their HRV and vital signs. Outcome measure: Descriptive analysis was carried out to summarize the subjects' profile. First, one way ANOVA was conducted to find out which demographic characteristic was affecting HRV. Second, repeated measure ANOVA was performed to find out if mental stress exerted an effect on the HRV. Finally, multiple regression was used to determine the predictability of HRV in relation to mental stress. Results: The results of the study were 1) absolute value of high frequency (HF) and total power (TP) of HRV and, 2) the square root of the mean squared differences of successive NN intervals (RMSSD) and standard deviation of NN interval (SDNN) of time domain of HRV were decreased by the mental stress, where the decrease in all the four parameters represented parasympathetic withdrawal. On the other hand, there was an statistically significant increase in very low frequency (VLF) and absolute value of low frequency (LF) of HRV by mental stress by which this increase represented sympathetic activation. Moreover, it was proved statistically that HF, TP, VLF, LF, LFnm, HFnm, RMSSD and SDNN had moderate to strong predictive power of the level of stress without the problem of multicollinearity. Conclusion: The mental stress in this study was able to stimulate parasympathetic withdrawal and sympathetic activation as measured by the HRV. HRV could be a reliable predictor for level of mental stress.

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