| Summary: | 碩士 === 國立交通大學 === 生物科技學系 === 98 === Heart rate variability (HRV) analysis has been used for many years to measure ANS activities for its simplicity, accuracy, and noninvasiveness. Recent studies show that HRV may be a powerful technique to measure the modulation and balance between parasympathetic nervous system (PNS) and sympathetic nervous system (SNS) by time and frequency domain analysis. It’s believed that decreased HRV is a sign of autonomic nerve system(ANS) imbalance, which may be caused by diseases, and with aging, the HRV decreases. Gender specific normal limits of HRV should be established to distinguish the normal decrease of HRV from pathological decreases in diseased conditions. The aim of the present study is to establish the gender dependent HRV normal limits in a healthy Taiwanese student population. Otherwise, posture differences of short term (5 minutes) time domain and frequency domain HRV parameters were analyzed to distinguish the different postures effect the ANS.
This study was performed at College of Biological Science and Technology, National Chao Tung University. A total of 115 healthy students from the university (57 males, aged 24 ± 1 years, and 58 females, aged 23 ± 5 years) without evidence of any heart disease by history and routine medical checkup were recruited for this study. The short term HRV recording was derived from the Modified Lead II-ECG, by a locally developed and manufactured device, DailyCare BioMedical’s ReadMyHeartR. All subjects were asked for lying, sitting, and standing each for 5-minute recording, and all of them must rest for at least 5 minutes before the measurement.
The statistically significant results differences from lying to sitting, lying to standing, and sitting to standing and the difference between genders on different postures were demonstrated. SDNN and RMSSD also decreased from lying to standing(P≦0.01, table 1), except lying to sitting of SDNN(P＞0.05). Total power, representing the autonomic tone, also declined from lying to standing (P ≦0.01, table 2 and 3), except lying to sitting. Both the HF and HF norm decreased from lying to standing (P ≦ 0.05). The LF norm and LF/HF ratio increased from lying to standing (P≦ 0.01).
From the results, we concluded that:
1. There was a statistically significant sex difference in frequency domain HRV parameters in all postures. The LF and LF/HF of male is greater than female in all postures. This might imply that sympathetic tone of male is higher than that of female.
2. The high HF of female is greater than male in all postures. This might imply that parasympathetic tone of female is higher than that of male.
3. There was a statistically significant posture difference in both time and frequency domain HRV parameters. The HRV of lying is greatest, and the HRV of standing is smallest.
4. HF component is the largest while lying, and LF and LF/HF are the largest while standing. This means that highest activity of parasympathetic tone while lying, and highest activity of sympathetic tone while standing.
5. While HF component is larger, HRV become larger. And while LF component and LF/HF are larger, HRV become smaller.
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