The Pulse Spectrum Analysis at Three Stages of Pregnancy

Abstract

Objectives:

This study is the first to detect the radial pulses of the three diagnosis positions (inch, bar, and cubit) in both wrists (six positions) by pulse spectrum analysis. The purpose of this study was to identify the difference among pulses of the six positions at three stages of pregnancy and to examine whether the results of this study agree with the theory of Traditional Chinese Medicine (TCM), which states that the cubit pulse shows unique changes for an expectant woman and that the pulse changes coincide with the progression of gestation.

Subjects and methods:

One hundred and fifty (150) healthy pregnant women were divided into three groups according to gestational age (9–14 weeks, 20–28 weeks, and 32–37 weeks of gestation) and 50 healthy nonpregnant women were used as controls. A pulse analyzer was used to detect the six positions of the radial pulses and to calculate the 10 relative energy values of the spectrum's harmonics of the six positions.

Results:

Results show that most of the 10 relative spectral energy values of the right and left cubits are statistically (p<0.01) higher than those of the inch for the pregnant women as compared with the nonpregnant women. In addition, the 10 relative spectral energy values of the six positions are not identical at the three stages of pregnancy.

Conclusions:

The cubit pulse is unique for pregnant women, which is consistent with the theory of TCM. In addition, the pulse conditions at the three stages of pregnancy are dissimilar.

Introduction

P regnancy is a special stage for women and it represents a serious challenge to the pregnant female's body. To support the developing fetus and to prepare the mother for parturition, women experience a series of physiologic changes that provide functional and structural adaptations at different stages of pregnancy.¹ The alteration of the cardiovascular system is the most profound physiologic change,² which starts early in the first trimester and plateaus by midgestation, peaking again around term.¹ In Western medicine, echocardiography is performed to evaluate the changes of pregnancy in cardiac structure, cardiac function, and uterine artery,^3,4 whereas in Traditional Chinese medicine (TCM), palpation is applied to evaluating the conditions of the expectant mother.⁵

Pulse diagnosis is a very important diagnosis method in TCM,⁶ which differs in Eastern and Western cultures.⁷ A doctor can take the radial pulse to evaluate whether a woman has conceived, to determine the weeks of gestation, and to predict the outcome of pregnancy.⁵ Descriptions of the pregnant women's pulse are abundant, as the Huangdi Internal Classic described, but opinions differ on this article.^5,8
–10 For example, some physicians explain that the slippery pulse is taken on inch at the first stage of pregnancy, but some describe that the slippery pulse is detected on the cubit during pregnancy. Nevertheless, most doctors have a consensus that the pulse condition of the cubit is specific for an expectant woman as compared with the inch pulse, and the pulse changes with the progression of gestation. In addition, there are differences among pulse conditions of the three diagnosis positions (cun, guan, chi [inch, bar, and cubit, respectively]) for pregnant women in some medical books.⁵

However, Western practitioners are often skeptical about pulse diagnosis because it appears subjective and not repeatable. Studies of the reliability of pulse diagnosis collected in a Chinese Medicine examination also suggest considerable variability, with results ranging from low to a very good level of agreement.^11,12 Therefore, several scientific and digital approaches to the pregnant pulse have been undertaken in recent years.^13

–16 For example, some studies have investigated arterial pulse wave parameters in normal pregnancy.^14
–16 The two methods that are often used to analyze the radial pulse pressure are time domain and spectral domain analyses.¹⁷ In time domain analysis, pregnant women are thought to have a higher ratio of slippery pulse and rapid pulse than nonpregnant women.¹⁸ * † From the comparative research on the pulse graphs and hemorheology between pregnant and pathological slippery pulses, we can discriminate the slippery pulses of pregnancy and illness.¹⁹ However, these studies of time domain analysis only provide a limited message that focuses on the slippery pulse. Thus, spectral domain analysis is applied to understand the hidden signal. For example, frequency parameters named phase transfer and phase variation character are used to identify the pulse between normal women and pregnant women.²⁰ Liang‡ first recorded the women's pulse spectra from the first trimester to postpartum and analyzed the change of harmonic components in bar pulse spectra according to the “Organs resonance” hypothesis of W.K. Wang. Although there were reports on the analyses of pulse conditions during pregnancy, few studies have been done on the frequency-domain analysis of pregnant women's pulses at three stages of pregnancy, especially the pulses of the three positions. Therefore, this study attempts to detect the radial pulses of the three positions in both wrists (six positions) at three stages of pregnancy using pulse spectrum analysis.

The purpose of this study is to identify differences among the pulses of the six positions at three stages of pregnancy and to determine whether the result confirms the theory of TCM, which states that the cubit pulse shows unique changes for an expectant woman and that the pulse changes coincide with the progression of gestation. The value of this study is that it provides an objective view of the pulse conditions in pregnancy and to help determine the specific pulse positions from the six positions that could be used to evaluate the pulse during gestation in the clinic.

Methods

Subjects

One hundred and fifty (150) healthy pregnant women and 50 healthy nonpregnant women were recruited to participate in this study. All subjects were between 20 and 40 years old. Healthy pregnant women without any acute or chronic disease were recruited when they visited the clinic in the obstetrics department in China Medical University Hospital, Taichung. They were divided into three groups of 50 women each according to gestational age: group 1 consisted of women of 9–14 weeks of gestation, group 2 consisted of women of 20–28 weeks of gestation, and group 3 consisted of women of 32–37 weeks of gestation. The mean age in group 1 was 30.5±3.29 years (mean±standard deviation), group 2 was 30.18±3.94 years, and group 3 was 30.52±3.37 years. Control group (group 4) consisted of 50 healthy nonpregnant women who were not under any medication that might influence menstruation. The mean age in group 4 was 27.98±5.45 years. All subjects signed an informed consent. This study was approved by the institutional review board of the China Medical University Hospital (DMR97-IRB-208).

Methods

A pulse analyzer (designed and patented by China Medical University, Taiwan), which consisted of a high-fidelity pressure sensor and a stable X-Y-Z axial moveable framework, was used to detect the radial pressure pulse of the three positions on both wrists. All subjects were in the sitting position during the experiment. Definitions of the three positions are as follows: the bar is just central to the radial styloid at the wrist, the inch is distal to this on the wrist, and the cubit is just proximal to it. The spectral analysis was performed to analyze the pulse: The pulse signal was digitized by fast Fourier transformation to obtain radial pulse spectra. Appearance of the first harmonic component in pulse spectrum was designated as the first harmonic. Then, these relative spectral energy values were calculated by integrating the harmonic components of the pulse spectra of the six positions. Since the signal of the 11th harmonic was too small to be valuable, only 10 harmonics were analyzed and 10 relative spectral energy values were obtained.

Statistical methods

Standard statistical methods were performed using the SPSS statistical program version 15. One-way analysis of variance (ANOVA) was used to analyze the difference of age among four groups. One-way repeated-measures ANOVA was applied to each group to identifying the difference of the six positions among 10 relative spectral energy values. A p-value of <0.01 was assumed to be significant. If the F value was significant, the Bonferroni test was used for pairwise comparison.

Results

All subjects completed the full course of pulse analyses in this study. There were no statistical significance (P>0.01) in the ages of four groups. Each of the four groups was analyzed and compared within group for the difference of the six positions among the 10 relative spectral energy values. The data of the four groups are combined and displayed in Tables 1 and 2. Table 1 is an example to show the statistical results of the first harmonic of the six positions. The relative spectral energy values are presented as mean±standard error. In the control group, most of the 10 relative spectral energy values of the right bar are statistically (p<0.01) higher than those of the inch or cubit. For example, the 10 relative spectral energy values of the 5th, 6th, and 9th harmonics of the right bar are statistically (p<0.01) higher than those of the inch in the control group. For pregnant women, most of the 10 relative spectral energy values of the right bar, right cubit and left cubit in the three groups of pregnancy are statistically(p<0.01) higher than those of the inch. For example, the 10 relative spectral energy values of the 5th to 10th harmonics of the right cubit are statistically (p<0.01) higher than those of the right inch in group 1 or group 2. In addition, the 10 relative spectral energy values of the 4th, 5th, 7th to 10th harmonics of the right cubit are statistically (p<0.01) higher than those of the right inch in group 3. Furthermore, there is a slight difference in the three pregnant groups, seen in higher relative energy values of the 4th to 9th harmonics of the left bar compared to those of the left cubit in group 3 as compared with those in group 1 or group 2.

Table 1.

Statistical Results of the Relative Energy Values of the First Harmonic of the Six Positions in Each of Four Groups

	Groups
Pulse positions	G1	G2	G3	G4
A	(4.91±0.22)×10⁻⁶	(4.47±0.27)×10⁻⁶	(4.10±0.29)×10⁻⁶	(5.22±0.33)×10⁻⁶
B	(5.16±0.24)×10⁻⁶	(5.08±0.36)×10⁻⁶	(4.68±0.27)×10⁻⁶	(5.94±0.41)×10⁻⁶
C	(4.48±0.23)×10⁻⁶	(4.33±0.26)×10⁻⁶	(4.58±0.25)×10⁻⁶	(4.51±0.34)×10⁻⁶
D	(5.12±0.25)×10⁻⁶	(4.96±0.29)×10⁻⁶	(5.22±0.35)×10⁻⁶	(5.55±0.32)×10⁻⁶
E	(6.09±0.33)×10⁻⁶	(5.02±0.37)×10⁻⁶	(4.79±0.27)×10⁻⁶	(5.64±0.37)×10⁻⁶
F	(4.80±0.28)×10⁻⁶	(4.26±0.20)×10⁻⁶	(4.68±0.25)×10⁻⁶	(4.48±0.34)×10⁻⁶
F value	6.16^*	2.8	2.37	6.69^*
Pairwise comparison	E>C,F			B>C,F; E>F

The data are presented as mean±standard error.

Significantly different (p<0.01) among six pulse positions. Pairwise comparison: significant difference on Bonferroni test.

G1, the group of pregnant women with 9 to 14 weeks of gestation (n=50). G2, the group of pregnant women with 20–28 weeks of gestation (n=50). G3, the group of pregnant women with 32–37 weeks of gestation (n=50). G4, the control group of nonpregnant women (n=50). The capital A indicates the right inch (the radial pulse read from the inch position on right wrist). B indicates the right bar, C the right cubit, D the left inch, E the left bar, and F the left cubit.

For example, the relative energy values of the first harmonic of the left bar is significantly higher than those of the right cubit or the left cubit in group 1.

Table 2.

Summary of Pairwise Comparisons (Bonferroni Test) of the Six Positions Among the 10 Relative Spectral Energy Values in Each of Four Groups

	C₁	C₂	C₃	C₄	C₅	C₆	C₇	C₈	C₉	C₁₀
G1	E>C,F	No significant difference	B>D,F	B,C,E>D	C>A,EB,C,E,F>D	C>AB,C,F>D	C,F>AC,F>D	C,F>A B,C,E,F>DC>B,E	B,C,F>AB,C,F>D	C,F>AC,F>D
G2	No significant difference	No significant difference	B>D,FC>F	B>A,D,FE>D	B,C,E>AB,C,E>D	B,C,E>AB,C,E>D	B,C,E,F>AB,C,E,F>D	B,C,E,F>AB,C,E,F>D	B,C,E,F>AB,C,E,F>D	C,E>AB,C,E,F>D
G3	No significant difference	No significant difference	B>AB,C>F	B,C,E>AB,E>DB,E>F	B,C,E>AB,E>DB,E>F	B,E>AB,E>DE>F	B,C,E>AB,E>DE>F	B,C,E,F>AB,C,E>DE>F	B,C,E,F>AB,C,E,F>DE>F	B,C,E>AB,C,E>D
G4	B>C,FE>F	B>C,FD,E>F	B>F	B>F	B>A,D,E,F	B>A,D	No significant difference	No significant difference	B>A,DE>A	C,E,F>A

G1, G2, G3, and G4 are defined as in Table 1. The definition of the capital letters are the same as in Table 1, A for the right inch, B the right bar, C the right cubit, D the left inch, E the left bar, and F the left cubit.

For example, in G1 group (the pregnant women of 9–14 weeks of gestation), the relative energy values of the seventh harmonic of the right cubit is significantly higher than those of the right inch or left inch, and the relative energy values of the sixth harmonic of the left cubit is significantly higher than those of the right inch or the left inch. In G4 group, there was no significant difference in the relative energy values of the seventh harmonic of the six positions. Comparing the results of group 1 with group 4, the differences can be clearly seen.

Discussion

This is the first study to detect the three positions of the radial pulses on both wrists using pulse spectrum analysis and to identify the difference among pulse spectra of six positions at three stages of pregnancy. Results showed that the 10 relative spectral energy values of the six positions are different in both pregnant women and nonpregnant women. It suggests that the pulse conditions of inch, bar, and cubit in each person are dissimilar, which conforms with the theory of TCM. In other words, the pulse can be affected by the six positions or left/right sides, which is consistent with previous studies that state the differences of pressure pulse waveforms and interarm pulse strength.^21,22 More importantly, the difference of the 10 relative spectral energy values of the six positions is more prominent between nonpregnant women and pregnant women. Furthermore, there is a slight difference in the three pregnant groups, which suggests that the pulse changes during the three stages of pregnancy are different.

In the nonpregnant group, most of the 10 relative spectral energy values of the right bar are statistically (p<0.01) higher than those of the inch or cubit. A previous study analyzed the pulses of the three positions in healthy people using time domain parameters and indicated that the amplitude of the percussion wave of the right bar was statistically higher than that of the inch and cubit.²³ However, few researchers have conducted spectral analysis of the pulses of the six positions in normal people.²⁴ Our result is in agreement with Huang's study that found that the power spectrum between 13 to 50 Hz in the right bar was higher than that in the inch or cubit.²⁰ Therefore, it could be stated that the pulse signal of the right bar is higher than that in the inch or cubit in nonpregnant women.

For pregnant women, not only are most of the 10 relative spectral energy values of the right bar but also those of the right and left cubits statistically (p<0.01) higher than those of the inch. Compared with nonpregnant women, the cubit pulse is unique for pregnant women. In TCM, the cubit pulse represents the kidney system involved in promoting reproduction and the function of the uterus. In other words, the cubit pulse is highly reflective of the reproductive system. Therefore, this result is consistent in the theory of TCM that the pulse condition of the cubit shows unique changes for an expectant woman. The cubit is the specific pulse position that could be used to evaluate the pregnant pulse in the clinic.

Results also showed that there are differences in the 10 relative spectral energy values of the six positions at three stages of pregnancy. It suggests that the pulse conditions at the three stages of pregnancy are dissimilar. For example, the relative energy values of 4th to 9th harmonic of the left bar were higher than those of the left cubit in group 3, which is an obvious distinction between group 3 and group 1, and between group 3 and group 2. It shows that the left bar pulse has a special meaning in late pregnancy. However, this observation needs to be further validated.

There are some aspects of this study that need to be improved. First, each person has their own constitution, and the difference of constitution between a pregnant woman and a nonpregnant woman is pronounced.^25
–27 The constitution could influence the pulse, so the issue of constitution must be added in the future to analyze the impact of the constitution on pulse. Second, this study was carried out through the four seasons. It is not known whether the seasonal effect on pulse is a factor involved in difference among the threes stages of pregnancy, although the pulse conditions in the four seasons are different by time domain analysis.²⁸ Therefore, the time of the experiment should be shortened to avoid experimental error in future studies. Third, all pregnant women were from the same hospital, which may result in increase of the sampling error. It is preferable to cooperate with several hospitals in the future to reduce the sampling error.

Conclusions

The pulse signals of the three diagnosis positions in both wrists of each subject are different. The spectral signal of the right bar is higher than that of the inch or cubit for nonpregnant women. More importantly, the cubit pulse is unique for pregnant women, which is consistent with the theory of TCM. Therefore, the cubit pulse is the specific pulse position that could be used to evaluate the pulses of pregnant women in the clinic. Furthermore, there are slight differences in the three pregnant groups, which shows that the pulse changes at different stages of pregnancy and the left bar pulses have special meaning in late pregnancy. This study provides an objective view for the pulses of pregnancy.

Footnotes

Acknowledgments

The authors wish to thank the support of the doctor and nurses of the obstetrics department in China Medical University Hospital.

Disclosure Statement

No competing financial interests exist.

*

Kou M. Objective research on 563 cases of pregnant women's pulse. Master's thesis of 2007 in Hubei college of traditional Chinese Medicine.

†

Chang BH. A study on the Chinese sphygmograms during the first and second trimester of pregnancy. Master's thesis of 1987 in Institute of Chinese Medical Science, China Medical University, Taichung County, Taiwan.

‡

Liang SJ. Analysis of harmonic components change in radial pulse spectra during pregnancy. Master's thesis of Institute of Integrated Medicine 2008, China Medical University, Taichung County, Taiwan.

References

Carlin

. Physiological changes of pregnancy and monitoring. Best Pract Res Clin Obstet Gynaecol, 2008; 22:801–807.

Dai

. Hemodynamic changes of blood flow in heart in pregnancy. Chin J Practical Gynecol Obstet, 2000; 16:403–404.

Chu

, Jiang

, Zhang

et al. Evaluation of the effects of pregnancy on cardiac structure and function with echocardiography. J Ultrasound Clin Med, 2008; 10:442–444.

Pan

, Sun

, Jiang

et al. The sequential study of uterine artery Doppler parameters in normal pregnant women. Chin J Practical Gynecol Obstet, 2006; 22:933–934.

Kou

, Wang

. Textual research of pregnancy pulse. J Tradit Chin Med Lit, 2006; 24:14–15.

. Research advances on diagnosis by feeling the pulse in clinical application. Gansu J Tradit Chin Med, 2007; 20:6–10.

Burns

, Burns

. Photoessay: Western frontier physician taking pulse. J Altern Complement Med, 1999; 5:401–403.

Zhou

, Zhang

. Discrimination of the pregnant pulse. Zhejiang J Tradit Chin Med, 2000; 35:36–37.

Bao

. The initial study of the pregnant pulse. J Gansu Coll Tradit Chin Med, 2004; 21:7,16.

10.

. Analysis of the pulse of pregnancy and delivery. J Tianjin Univ Tradit Chin Med, 1999; 18:1–2.

11.

O'Brien

, Birch

. A review of the reliability of traditional East Asian medicine diagnoses. J Altern Complement Med, 2009; 15:353–366.

12.

O'Brien

, Abbas

, Zhang

et al. Understanding the reliability of diagnostic variables in a Chinese medicine examination. J Altern Complement Med, 2009; 15:727–734.

13.

Bai

, Zhao

, Wang

. Analysis of pulse signal based on wavelet transform zero-crossing. Space Med Med Eng, 2006; 19:204–207.

14.

Macedo

, Luminoso

, Savvidou

et al. Maternal wave reflections and arterial stiffness in normal pregnancy as assessed by applanation tonometry. Hypertension, 2008; 51:1047–1051.

15.

Smith

, Morris

, Gallery

. Methods of assessment of the arterial pulse wave in normal human pregnancy. Am J Obstet Gynecol, 2004; 190:472–476.

16.

Khalil

, Jauniaux

, Cooper

et al. Pulse wave analysis in normal pregnancy: A prospective longitudinal study. PLoS One, 2009; 4:e6134.

17.

. The objectivity and digital of diagnosis by pulse based on traditional Chinese Medical science. Liaoning J Tradit Chin Med, 2006; 33:129–131.

18.

Zhang

, Zhang

. The evaluation of slippery pulse for diagnosis of early pregnancy. J Tradit Chin Med, 1993; 13:276–277.

19.

Chen

, Niu

, Dong

et al. Comparative research on pulse graph and hemorheology of pregnant and pathological slippery pulse. China J Tradit Chin Med Pharm, 2008; 23:34–36.

20.

Zhai

, Ning

, Liu

. Pulse signal analyzing system and frequency identification between normal women and pregnant women pulses. J Nanjing Univ (Nat Sci), 2000; 36:448–454.

21.

, Wei

, Hsieh

et al. Influence of menstrual cycle on pulse pressure waveforms measured from the radial artery in biphasic healthy women. J Altern Complement Med, 2009; 15:645–652.

22.

King

, Walsh

, Cobbin

. The testing of classical pulse concepts in Chinese medicine: Left- and right-hand pulse strength discrepancy between males and females and its clinical implications. J Altern Complement Med, 2006; 12:445–450.

23.

Zheng

, Wang

. Preliminary study for 45 sphygmograms of normal young people. J Yunnan Coll Tradit Chin Med, 1994; 3:25–27.

24.

Huang

. The science of sphygmographs for modern pulse diagnosis. Jyin Publishing House, Taipei, 2007; 125–130133–134.

25.

Pan

, Pan

, Zhou

. The Chinese constitution's distinction of pre-pregnant women by the properties of menstruation and leucorrhea. J New Chin Med, 2007; 39:8–9.

26.

, Wang

, Cui

. Clinical discussion on female constitution. Shaanxi J Tradit Chin Med, 2007; 28:853–855.

27.

Zhuang

, Li

, Zhang

et al. Chinese physique distinguishing patterns used in pregnant and parturient woman. Chin Arch Tradit Chin Med, 2009; 27:782–783.

28.

Tang

, Yang

, Dai

. The study on the effects of seasonal change on the pulse. Liaoning J Tradit Chin Med, 2008; 35:1834–1835.