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ORIGINAL ARTICLE
Year : 2023 | Volume
: 9
| Issue : 4 | Page : 469-474
Close correlations between carotid arterial mean blood flow velocity, body mass index, and temperature in normal individuals
Xiang Zhu, Wei Gao, Yong Chi, Zhi-Yong Wang, Jun-Jie Shao
Department of Traditional Chinese Medicine, Shanghai Sanfamily Clinic, Shanghai, China
Correspondence Address:
Dr. Jun-Jie Shao
Department of Traditional Chinese Medicine, Shanghai Sanfamily Clinic, Shanghai 201114
China
Source of Support: None, Conflict of Interest: None
DOI: 10.4103/2311-8571.391117
Objective: Assessing carotid and radial pulses is an essential sphygmology method in traditional Chinese medicine (TCM). It is believed in TCM and by doctors that pulse force is markedly linked with the physiological state of a human, including body mass index (BMI) and temperature. However, comprehensive analysis elucidating these potential correlations remains undetermined. Therefore, this investigation aimed to assess the association of pulse strength with human metabolism. Materials and Methods: The mean blood flow velocity (MBFV) of the carotid artery and pulse force of 122 healthy adults included in this investigation were assessed using ultrasound and manual palpation. Their thermal texture map was also acquired. Results: No substantial variation was observed in the carotid arterial MBFV among normal individuals (P > 0.05) regardless of body side and gender. However, young individuals had higher blood velocity than middle-aged individuals (P < 0.05). Furthermore, it was identified that MBFV was negatively associated with BMI and torso temperature; however, it was positively linked with hand temperature. Conclusions: This investigation revealed that carotid arterial MBFV could indicate the physical state of humans, including BMI and temperature, and therefore, is valuable for elucidating the effect of TCM on yin–yang. The data validated some TCM beliefs and supported the implementation of sphygmology in TCM.
Keywords: Body mass index, carotid artery, mean blood flow velocity, sphygmology, temperature, traditional Chinese medicine
Manual palpation assessment of radial and carotid arteries is a traditional pulse-taking protocol utilized to diagnose meridian diseases in traditional Chinese medicine (TCM).[1],[2],[3] According to TCM theory in Western medicine, the carotid artery or Renying pulse (RP) is a part of the stomach yang meridian, and it identifies yang in healthy conditions and indicates heart and arterial system functions. The radial artery or Cunkou pulse (CP) is a lung yin meridian component crucial for the prognosis and treatment strategies of conditions involving yin elements. Huang Di Nei Jing, a classical TCM text, stated that RP forces indicate the functional and physical states of individuals.[4],[5],[6] For instance, in the case of weak RP strength, the yin element dominates the body, lowering the temperature.[3],[5],[6] An individual with a lean body releases enhanced heat than an overweight individual because of reduced yin.[3],[5],[6] However, the data supporting these TCM theories require elucidation. Although many research exist on the properties of the radial artery, the study on the carotid artery is scarce.[7],[8],[9],[10],[11],[12] Therefore, this investigation explored the potential association of RP with the human physiological state to furnish evidence on TCM assumptions.
Materials and MethodsSubjects
A total of 122 individuals (57 males 40.05 ± 2.68 years old with 175.06 ± 2.08 cm height and 70.23 ± 8.29 kg weight; 65 females 40.29 ± 1.73 years old with 160.38 ± 5.45 cm height and 60.56 ± 6.57 kg weight) aged 20–60 years, without underlying medical conditions and not on medication, were included in the study. The individuals were divided into the young age (20–40 years old) and middle-aged (41–60 years old) groups [Table 1].
Exclusion criteria
Individuals with psychological disorders, pregnancy, wounds/scars at the pulse measuring site, atherosclerosis, arrhythmia, arterial thrombosis, diastolic blood pressure <60, body mass index (BMI) <17 or >30, systolic blood pressure >140, and menstruation were excluded from the study.
All procedures performed in the study involving human participants were in accordance with the ethical standards approved by the Review Committee of Oriental Ruijin Hospital, Shanghai, China (No. KY2020-360).
Experimental equipment
This investigation utilized SonoScape S15 (SN3026759) color Doppler ultrasonic diagnostic apparatus equipped with a 5-13MHz vascular probe (SonoScape Medical, Ltd. Guangdong, China). A TSI-2000 thermal texture map (TTM) and a thermography camera (measurement range = 20°C to 60°C and pixels resolution = 640 × 480) were utilized to assess body temperature and thermographic images, respectively (Bioyear Group, Ltd, Beijing, China).
Manual pulse measurements
Each participant's pulse was measured by a TCM doctor in a quiet room at a constant temperature of 24°C and 26°C and 40% and 60% humidity. Before the pulse assessment, all the participants rested on a comfortable bed for 30 min. The carotid artery was assessed manually with the participants in the supine position. The RP was located at the carotid artery along the anterior border of the sternocleidomastoid muscle. The doctor tested the pulse force through fingers, classified the strength as weak, medium, and strong, and quantified it as 1, 2, and 3, respectively. The weak pulse was determined by lightly placing the fingers over the carotid artery without pressure. For a strong pulse, enough pressure was applied to the carotid artery to block it, and then the pressure was gently released until the pulse was felt again. Then, the pulse equalized. Medium pressure between the two previous levels was applied for the medium level. During relative force measurement, the participants were asked for feedback about the applied pressure to elucidate if the doctor was simultaneously applying equal pressure at the left and right neck for each level. All measurements were taken thrice.
Carotid arterial mean blood flow velocity measurement and analysis
For assessing carotid arterial mean blood flow velocity (MBFV), all the individuals rested for 30 min, and the MBFV was assessed with the participant in the supine position. The same pulse sites were checked for manual pulse assessment. A duplex ultrasound with a two-dimensional Doppler probe (5–13 MHz) was utilized by adjusting the ultrasound beam's direction at 30° and 45° angles, which were minimized to possible levels. The MBFV was continuously measured for 16 s, digitized, and saved as time-series data until subsequent use. The arterial MBFV waveforms were ensemble averaged for 10 consecutive pulses.
Thermal texture map measurement
For this experiment, the participants rested without clothes for 10 min in a room with a set temperature (20°C and 24°C) and humidity (40%–50%) in a way that their hands would not touch the body. TTM was generated for many positions: dorsally, laterally on both sides, and anteriorly, and the images were acquired by a fixed camera about 70 cm away from the participant. The temperature was defined as cold and warm weather based on seasons. In the northern hemisphere, winter and spring start on the November 1, and end on the April 30, and summer and autumn begin on the May 1, and ends on the October 31. For precise measurements, the participants were assessed in two different seasons.
Body mass index measurement
Self-reported weight and height within ± 2.0 kg or ± 2.0 cm, respectively, were accepted. This investigation followed the World Health Organization BMI classification.[13]
Statistical analysis
All the values were depicted as the mean ± standard deviation and were measured through SPSS version 15.0 (SPSS Inc., Chicago, IL, USA). The intergroup differences of intrinsic and extrinsic variables were assessed by independent t-test. The serial changes of the three groups were measured by two-way variance analysis (ANOVA). P <0.05 was termed statistically important, and the significance levels were marked as * P < 0.05, **P < 0.01, and ***P < 0.001. The two methods' consistency was identified according to the intraclass correlation coefficient (ICC) and respective 95% confidence interval.
ResultsCorrelation of mean blood flow velocity between ultrasound and manual palpation
Initially, the ICC test elucidated if MBFV assessed from ultrasound was consistent with manual palpation. The ICC values by manual and machine protocols were 0.746 and 0.773 on the right and left sides, respectively, suggesting that machine MBFV had a positive correlation with manual palpations [Figure 1]a and [Figure 1]b.
Figure 1: Relationship between carotid artery mean blood flow velocity and pulse force on the left (a) and right (b) sides. Carotid artery mean blood flow velocity was tested by ultrasound, while the pulse force was examined, quantified, and recorded by a doctor. Then, the mean blood velocity was calculated and compared with the pulse force results, which were presented as numbers, showing the strength of the pulse. (1: weak, 2: medium, and 3: strong) The test of ICC was used to assess the consistency between blood velocity and pulse strength. For the left side (a), 95% CI = 0.687–0.838). For the right side (b), 95% CI = 0.652–0.818). ICC: Intraclass correlation coefficient, CI: Confidence intervalMean blood flow velocity based on the body side and gender
No substantial differences in MBFV results were observed for the left and right body sides [Figure 2]a. On closer examination, the average carotid pulse mean velocity was observed as 60 cm/s, providing overall arterial velocity values of normal individuals. [Figure 2]b depicts similar arterial MBFV in both genders.
Figure 2: Relationship between carotid artery mean blood flow velocity and influence factors. Carotid artery mean blood flow velocity from normal individuals was examined through an ultrasound. The correlation of values concerning both intrinsic and extrinsic parameters, such as side (a), gender (b), age (c), and surrounding climate (d) was shown in the graph. Data were expressed as means ± standard deviation. The ratios were analyzed by independent t-test. NS: Not significant P > 0.05, *P < 0.05Mean blood flow velocity for different ages and weather conditions
[Figure 2]c compares MBFV values in different age populations. The young (≤40 years) cohort had significantly higher values than the middle-aged (>41 years) cohort. The association of temperature (referring to the surrounding climate) with MBFV revealed no substantial difference in cool (70 cm/s) and warm (65 cm/s) climates [Figure 2]d.
Carotid arterial mean blood flow velocity is inversely related to body mass index
It was indicated that reduced MBVF corresponded to elevated BMI. Increased variability in the values was identified between weight/height-based groups. The arterial MBFV in the lightweight cohort was about 80 cm/s, whereas that of the overweight cohort was <50 cm/s [Figure 3]a.
Figure 3: Relationships between the carotid artery mean blood flow velocity, BMI, and body temperature. BMI and blood velocity were collected by self-reported documents and ultrasound, while the same group was scanned by thermal texture map. The relation between blood velocity and BMI (a) was shown in the graph. The correlation between the temperature of the torso (b) and hands (c) regarding the blood velocity was demonstrated in the graph. Data were analyzed using a two-way analysis of variance followed by Tukey's post hoc test. Values were expressed as means ± standard deviation. NS: Not significant P > 0.05, *P < 0.05, **P < 0.01, and ***P < 0.001. BMI: body mass indexBody mass index negatively correlated with human torso temperature
After elucidating the association of MBFV with BMI, the potential link between body temperature and BMI was assessed. [Figure 3]b depicts reduced torso temperature with increased BMI. The torso temperature markedly varied between the overweight and low-weight participants with different MBFV [Figure 4]. Interestingly, hand temperature was positively associated with BMI; that is, higher BMI levels corresponded to increased hand temperatures [Figure 3]c. As [Figure 4] illustrates, the hand temperature of heavier individuals was higher than those with a lower weight.
Figure 4: Images of thermal texture map (TTM) results on the relationship between carotid artery blood flow velocity, BMI, and body temperature. Two young women with different blood flow velocities and BMI were scanned by TTM in Summer (a). Two middle-aged men with different blood flow velocities and BMI were examined via TTM in Winter (b). The TTM examinations were performed in several positions, and images were recorded. BMI: body mass index, MBFV: Mean blood flow velocity Discussion The assessment of RP and CP is important TCM diagnosis protocols, representing the human body's yin–yang state. However, RP testing must be addressed due to its inconvenient assessment protocol. Moreover, many research focus on CP; for instance, King et al. studied 148 healthy individuals for characteristic radial pulse profiles in both genders.[7] Yim et al. indicated gender and position-based physiological variations in radial pulse.[8] Lus et al. investigated RP and CP; however, the hypertension group did not include normal individuals.[11] Therefore, investigation of the characteristics of carotid arteries in a healthy cohort using modern methods is necessary to depict the importance of RP assessment.
The literature suggests multiple protocols for standardizing TCM pulse diagnosis; however, limitations exist.[10],[12],[14],[15],[16] For example, pulse wave velocity (PWV), an arterial stiffness index, can only evaluate the pressure pulse traveling speed between the two given points in a limited time.[16] Hodis doubted the reliability of PWV for the thick arterial walls.[17] The augmentation index is another tool to measure pulse amplification, but it is unsuitable for comparing pulses as the calculation method between the two arteries needs coherence.[18] Manual pulse examination is subjective; therefore, validating the link between manual and machine measurements is crucial. This investigation identified the following MBFV parameters: End-diastolic velocity (EDV) and peak systolic velocity (PSV), both critical hemodynamic parameters. PSV is an index for blood vessel filling and blood supply strength. EDV depicts blood perfusion.[19] This investigation proved that MBFV, comprising PSV and EDV, was suitable for representing the pulsating force and fluidity of pulsations checked by hand.[19] Furthermore, healthy individuals depicted carotid arterial MBFV of about 60 cm/s. In TCM, manual pulse analysis by hand is unique, but the result might be affected by subjective factors such as the doctor's mental emotion or finger sensation. Therefore, in this research, an ICC test was carried out, which proved that the ultrasound result could reflect the hand feeling from a TCM doctor as the consistency between MBFV from the machine and pulse strength from fingers is high, laying a solid foundation for future investigations.
Huang Di Nei Jing mentions RP 47 times, demonstrating its importance in TCM theories.[4],[5] Furthermore, it also indicated that pulse force markedly regulates yin–yang balance,[2],[5],[6] suggesting that strong RP in humans indicates yang is increased than yin, causing enhanced heat, and vice versa. According to TCM yin–yang theory, young people have more yang than the middle-aged and are more frequent in summer than winter.[2],[6] Moreover, Western medicine indicates that aged blood pressure and cardiovascular system alterations cause radial and carotid artery response.[10] Although this investigation revealed no gender-based differences in velocity, according to some TCM physicians, the difference is believed to be associated with gender.[2],[3],[7],[8]
The TCM texts on pulse diagnosis are rooted in the yin–yang theory, which also guides acupuncture and TCM prescription. For instance, Monkshood, an herb considered with heat, is usually used for people with yang deficiency. In general, the yin–yang nature of the human body can be quantified through temperature monitoring equipment because it represents the biological metabolism that is a process of heat generation. According to the TCM theories, overweight individuals had reduced heat and yang deficiency, and leaner individuals had increased heat and weak yin.[4],[6] Furthermore, ancient TCM texts elaborate on this phenomenon as the insufficiency or hyperactivity of yin and yang, causing a qi or blood imbalance.[2],[6],[20] We believe that blood and qi indicate the body's moving energy, identified and elucidated by modern metabolic markers, including temperature and BMI. Here, the TTM revealed substantial differences in body temperature between the overweight and low-weight cohorts. TTM pictures indicated that in overweight individuals, low-temperature adipose tissue surrounded the torso, and lean individuals with less subcutaneous fat had increased surface temperature. Furthermore, overweight individuals had reduced carotid MBFV than low-weight individuals. The arterial MBFV indicates the yang and yin balance, illustrating a logical relationship between arterial MBFV and temperature in humans. In addition, hand temperature is positively linked with BMI. However, this finding could not be explained because of a lack of knowledge. Further investigations with increased participant size are needed.
ConclusionsElucidating carotid arterial MBFV and its properties furnishes evidence about the association between human BMI and body temperature. This investigation revealed that the pulse force and yin–yang properties accord with healthy humans' temperature and validate TCM theories, suggesting a need for further demographic investigations to establish and elaborate TCM assumptions.
Ethics approval and consent to participate
The human experiments were approved by the Institutional Review Board of Oriental Hospital of Ruijing Hospital, Shanghai, China (approval no. KY2020-360).
Authors' contribution
SJJ designed the study. ZX participated in the study design. ZX, GW, and CY performed the research and wrote the manuscript. CY and WZY analyzed the data. All authors read and approved the final manuscript.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
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