The pulse: its place in contemporary biomedical and CM practice

The circulatory system functions as a transportation system. It distributes the nutrients and substances required for healthy metabolism to tissue cells and organs while removing metabolic waste from those same cells and organs. According to Berne & Levy (1981: p. 1) the components of the circulatory system can in their simplest form be reduced to a pump moving fluids through a distributing network of tubes. Yet this analogy of the circulatory system is overly simplistic when the circulatory system is considered within the context of health. Rather than the passive distributing network implied in the analogy, it is actually a dynamic regulatory system assisting in the maintaining body temperature; regulate volume flow of blood; and act as a communication network between different body regions. These functions of the circulatory system depend on controlled changes in the width of blood vessels (vasoconstriction and vasodilatation) and the pump-like action of the heart to cause blood flow. These functions are all mediated through an innate biofeedback system which helps maintain homeostasis and organ function. For example, by reducing the blood vessel diameter (vasoconstriction), the surface area of the blood vessel exposed to the environment also decreases and body heat is retained while concurrently reducing blood flow to the superficial and peripheral regions of the body. Increasing blood vessel diameter (vasodilatation) increases the surface area of the blood vessel, thus increasing the rate at which body heat is lost to the environment. The supply of nutrients circulating to the tissue cells is regulated by this same vasodilatation/vasoconstriction mechanism. Chemical transmitters, hormones and other chemical markers produced by the body and required for regulating homeostasis are similarly distributed in this manner.

The body’s organs and tissues have varying nutritional and blood flow requirements for their health and normal functioning. Such requirements also vary depending on the time of day and level of activity. This is reflected in the differing density and type of blood vessels found in different regions of the body. For example, the skin has small requirements for copious blood flow and so the capillary network is fine but densely distributed; useful in times of tissue repair due to trauma or for dispersing body heat during exercise. On the other hand, the brain has a high and constant requirement for blood flow and several large arteries serve this purpose by maintaining a continuous supply of blood flow to the organ, while the lungs are rich in small capillary beds to assist in the transfer of metabolic waste for oxygen. Similarly, other organs vary in both the density of blood vessels present and anatomical structure of the vessels depending on function and purpose. The kidneys in particular have a unique circulation, using specialised arterial structures to increase partial blood pressures to filter toxins from the blood.

These concentrations of blood vessels that serve such a specialised function can be termed a microcirculation. Berne & Levy have noted that some chemicals, whether intrinsic or introduced by therapeutic interventions, may have differing affects on the microcirculation and on arterial smooth muscle:

In the context of health assessment, it is logical to conclude that dysfunction or increased demands on an organ, whether in response to neural, hormonal or chemical stimulus, should mean that the circulatory requirements, and hence the microcirculation of that organ, would be affected.

Extrapolating about Chinese medical ideas then, it is not inconceivable to link such microcirculatory changes posited by Berne and Levy to Chinese medical ideas on pulse diagnosis. In this sense, it can be that such microcirculatory changes when applying CM theory, are detectable elsewhere in the body, and in particular in the radial artery, via signals carried in the haemodynamic pulse wave. Dai et al (1985) hypothesised and demonstrated that disturbances in the arterial blood flow in one region of the body can be detected elsewhere in the body using the arterial pulse wave. They did this through intermittent occlusion of blood flow in the right leg, showing a corresponding reduction in the force level of the pulse in both left and right radial arteries (using pressure transducer measurements). Therefore, it is not illogical to state that changes in an organ’s microcirculation would similarly affect arterial haemodynamics detectable elsewhere in the circulatory system.

At any given point in time, the pulse should reflect the circulatory system’s ability to undertake the distributing and regulatory functions described above. What is described as a ‘pulse’ in the clinical context is foremost, and always, a product of the circulatory system, generated by pressure changes which occur with heart movement. In this context, pulse diagnosis is used to assess heart movement, measuring the rate or frequency of pulse occurrence and whether this is occurring in a rhythmic fashion. From the assessment of pulse movement, it is inferred that the heart is moving and functioning in a particular fashion. Yet these two ‘movement’ characteristics, rate and rhythm, do not adequately explain or describe the range of information that CM literature, or indeed biomedicine, claim as being able to obtain from assessment of the pulse. Thus, in addition to pulse rate and rhythm, there are several other characteristics of the pulse that are assessed. (These are discussed in Chapter 6 and Chapter 7.) In a CM diagnostic framework, each is used to infer the function of a particular aspect of the body via the degree of change occurring in each of the pulse characteristics. The practitioner aims to determine whether the perceived changes in the pulse have arisen due to internal organ function, compromised blood flow, or external conditions such as viruses, bacteria or other environmental factors. It is the body’s response to these factors or attempt to maintain homeostasis or balance which is of interest in the process termed ‘pulse diagnosis’. Investigation and observation of changes in the pulse and their attribution to health is the aim of pulse diagnosis. This leads us to the next question — exactly what is the pulse?

The pulse is a physiological phenomenon propagated throughout the arterial system. It is generally viewed as a travelling pressure wave caused by the rhythmic contraction and relaxation of the heart. Thus the pulse can be described in terms of systole, when the pulse amplitude increases or the heart contracts; and diastole, when the amplitude decreases or the heart relaxes (Box 2.1). A pulse can also be thought of in terms of any regular movement or change in differential pressure that manifests as a rise and fall of fluid in a vessel. In terms of clinical practice, a ‘pulse’ is usually associated with a palpable pressure movement. For example, the radial artery, located at the wrist overlying the radius, is a major site at which to feel the pulse.

The pressure wave produced with heart movement is often considered the ‘pulse’, but for purposes of pulse diagnosis using manual palpation the pulse encompasses more than the pressure wave alone. In addition to pressure waves, O’Rourke et al. (1992) note the pulse also encompasses flow waves; the actual movement of blood. They note there is even a third type of wave called diameter waves produced with vessel diameter changes, but these waves are very similar to the pressure wave (O’Rourke et al 1992: p. 17) and, as such, will not be discussed any further in this book. Each of these waves is distinctly different when looking at objective measurements of their contours. Therefore, what is regarded as a single ‘pulse wave’ is in fact a composite of at least two different types of waves. There is the pressure wave, the actual force caused by heart movement, and there is the flow wave, determined by how the pressure wave acts on the actual flow movement of blood. How each contributes to the overall pulse formation probably determines the spectrum of diverse pulse qualities in the CM literature.

In the context of health, it is important to understand that the pulse wave is not a static artefact of heart movement, nor does the pulse remain in constant shape as it moves through the arterial system. It is rather in a constant state of change, acted on by the characteristics of the vessel conduit, the functional state of the organs and tissue and the quality of blood itself, which is in turn determined by the state of health of the individual. It is the cumulative effect of the whole range of these factors that moulds the pulse wave into the pulse that eventually arrives at the radial artery as felt by practitioners. Therefore, the essential characteristics of how the pulse presents to the practitioner when palpating the pulse infer the nature of illness and an individual’s state of health, an intimate ‘record’ of the bodily environment. Pressure waves, flow waves and blood are discussed in further detail below.

Blood is an important component of the formation of the pulse. It is a complex fluid, composed of a plasma liquid base and several formed particles, the most prominent of which are red blood cells, which make up 99% of all particle types found in blood. Other components include:

For these reasons blood is referred to as a liquid tissue. Blood is the medium in which the pulse wave propagates from the heart to the periphery. Therefore, changes in the blood medium — that is, changes in any of the ratio of its components — will affect the propagation of the pulse wave. Changes can occur in a number of ways. They can arise due to illness, from trauma producing blood loss, or from diet where an individual’s inadequate intake of appropriate food groups adversely affects the quality and quantity of the blood. In this way, the ratio of the different cell components of blood can vary between people and can vary within the same individual over time. Blood may consequently ‘thicken’ or ‘thin’. The relative degree of ‘thickness’ is termed viscosity.

Blood viscosity depends on the ratio of cells to plasma in the blood. The higher the proportion of cells, the denser or more viscous is blood. This means that blood becomes more difficult to move through the blood vessels as resistance to its smooth flow increases. For example, polycythemia is a state in which the red blood cell ratio is raised, causing blood to become more viscous. In this state blood flow fluidity is affected, flow velocity slows and blood pressure becomes raised due to increased resistance to its flow in the vessels. Chronic smoking, athletic training and high altitudes can all cause an increase in the ratio of red blood cells. An increased demand for oxygen by the body causes an increased number of red blood cells to assist with oxygen transportation. The concentration of red blood cells can also increase when fluid is lost from the blood plasma through dehydration or burns. Alternatively, dietary intake of iron may fluctuate depending on food sources. Eventually, this also affects blood through changes in the red blood cell ratio and changes in blood viscosity, and changes in the pulse wave will consequently also occur. For example, the decreasing iron levels and haemoglobin associated with anaemia are often accompanied by regulatory changes in blood pressure via vasodilatory mechanisms in an attempt to maintain homeostasis as red blood cell ‘quality’ and ratio decrease. This in turn affects the propagation of the pressure wave and resultant flow wave. Additionally, sudden loss of blood volume due to haemorrhage (cells and fluid) also affects pressure and flow waves. Interestingly, blood volume can also decrease when fluid moves out of the blood plasma, as occurs in dehydration.

The pulse is a physiological phenomenon propagated throughout the arterial system and can be viewed as an indication of the circulatory system’s capacity to undertake the distribution of essential substances required for metabolism to body tissue and organs. In the context of health, the pulse is a complex physiological sign and can be described in terms of systole and diastole. It is primarily composed of pressure waves (including reflective waves), and flow waves.

Once produced, a pulse wave undergoes a series of changes as it moves from the heart or central regions of the body into the peripheral blood vessels of the arms and legs. By the time the pulse wave arrives at the radial artery it may have a distinctly different shape and contour than it had when initially produced by the heart. Variables that influence the presentation of the pulse as felt with palpation at the radial artery include:

These, in turn, are influenced by the neural, hormonal and chemoregulatory systems for blood pressure and maintaining blood flow for purposes of homeostasis or balance in health and illness. A change in health status affects homeostasis balance, which in turn affects the pulse.

The procedure of pulse palpation is termed sphygmology, literally meaning ‘the study of the pulse’. The term sphygmos derives from Greek meaning literally a pulse or throb. In contemporary biomedical practice the pulse is used in the assessment of several conditions mainly affecting circulation and reflecting heart function. The pulse is primarily viewed as a product of the heart and compliance of the vascular system, and is highly dependent on the use of sophisticated devices able to record and measure variables quantitatively. Accordingly, the term pulse palpation is largely used with reference to the determinant of pulsatile strength, heart rate and heart rhythm by manual palpation. Yet pulse palpation has not always been used in this manner within biomedicine; it once had an equally broad application for identifying ‘qualitative’ changes in the pulse, as is still claimed in CM.

The principles of sphygmology are derived from the works of ancient Greek physicians, in particular Galen (131–199 ce) (Naqvi & Blaufox 1998), but can be traced back even further to Hippocrates (approximately 450–350 bce). Other important historical figures in the development of pulse in the health assessment process included Aegimius, whose writings founded the concept of pulse as a diagnostic technique; Rufus of Ephesus and his treatise Synopsis on Pulses; and Herophilus of Alexandria, the reputed founder of sphygmology (Bedford 1951, Hsu 2005, Kuriyama 1999, Lloyd 1996). But it was Galen’s prolific discourse on the use of pulse in assessing health, including commentaries on the pulse writings of his predecessors, which meant his thinking on pulse would dominant the practice of pulse by subsequent occidental medical healers.

Galen’s interpretations and descriptions of pulse characteristics have more in common with the CM view of the pulse than with modern biomedical principles. They include differentiating pulse speed, length, width and depth to the body’s homeostasis, and describing them in terms of excess or deficiency depending on the presenting pathology. Variables affecting the pulse presentation were listed as including age, seasons, food, pregnancy and the environment. The pulse was also referred to in terms of organic pulses; authors later interpreted organic pulses as an extension ‘by which each organ imparted its personality to the pulse’ (Bedford 1951: p. 428). That is, specific pulse types were specifically seen as arising from different organs.

Pulse diagnosis in the intervening centuries since Galen’s time remained largely dependent on his books on the pulse, even in times when a more ‘scientific’ or physiologic basis for circulation of the pulse was described by Harvey in the 16th century. For example, Naqvi & Blaufox (1998: p. 24) note Theophile Bordeu (1722–1776) in his 1756 publication Recherches sur le pouls describing the ‘gastric pulse’, ‘renal pulse’ and ‘uterine pulse’ as arising specifically from the organs. Unfortunately, Galen’s extensive writings were plagued with descriptive anomalies which meant clinical interpretation was variably successful with physicians just as often disagreeing on the meaning of a pulse as agreeing (Kuriyama 1999).

As an aside, with reference to Chinese medicine, Hsu notes that the language of pulse remained descriptive, even in later centuries as pulse knowledge accumulated. Pulse qualities continued to be likened to descriptive imagery; practitioners associated pulse sensations to what they saw in the environment around them (Hsu 2005). Such an observation regarding the descriptive use of language in Chinese medicine is equally applicable to pulse terminology in the Western traditions and even into contemporary times. For example, the Steel Hammer pulse is compared to the resounding ring of a hammer blow. This perhaps describes the lack of expansion of the artery on pulsation and the resonance felt by the practitioner’s palpating fingers. These descriptions used by these classical occidental practitioners to describe the various presentations of the radial pulse would have had a resonance for contemporary CM practitioners. For example, terms such as tense, wiry and thready were variously used to describe different qualitative aspects of the pulse (Table 2.1). Some of these pulse terms continue to be used in modern cardiology units and for general health assessment.

From the 16th/17th centuries, the traditional practice of pulse diagnosis, still based on Galen’s work, was radically challenged in two ways. The first was the emerging understanding of blood flow as a single circulatory system, as established by Harvey in the early 17th century. The second was the increasing experimentation of recording pulse waves objectively using mechanical devices. Objective measurements were free from the observer’s personal bias; this meant a recording of the pulse wave could be simultaneously observed and discussed by several practitioners, thereby removing the ambiguity of pulse interpretation that had plagued the technique in past centuries.

By the late 19th century the arterial wave form was being regularly recorded using sphygmograms. For example, Figure 2.6 illustrates such a recording originally published in 1906. Such recordings of the radial arterial waveform were made by mechanisms attached to the wrist region over the radial artery. The pulsations would displace these mechanisms and produce tracings, which were referred to as sphygmographs. In the context of clinical practice, the physician concentrated on deciphering the sphygmograph and its relationship to a patient’s health and any disease present.

Yet while objective pulse measurements were obtainable using these mechanical devices, quantitative measurement was not the primary purpose of these recordings. Rather the measurements were obtained to visualise the contour of the pulse waveform being palpated (Fig. 2.6).

However, at the end of the 19th century, the pulse and its use in clinical practice was radically changed when Riva-Rocci introduced into clinical practice the indirect method by which arterial blood pressure was objectively measured. This involved using a mercury manometer, the forerunner of the present-day brachial cuff sphygmomanometer (Naqvi & Blaufox 1998). Eventually, the focus on the sphygmomanometer, as described by O’Rourke et al (1992), saw the descriptive terms diastolic and systolic supplant a range of ‘qualitative’ variables that, until that time, had had high clinical significance placed on them.

This changed perception of the significance and relevance of the pulse wave qualities in clinical diagnosis was not so surprising, according to Kuriyama (1999), since there had always been doubt within the medical fraternity concerning the use of pulse diagnosis to inform diagnosis. The subjective nature of pulse diagnosis, and the inability of the physicians to agree on pulse interpretation, were clearly seen as reasons for this.

In CM, the process of pulse diagnosis is termed qie mai. Mai derives from a Chinese character meaning a vessel and can equally be applied to blood vessels and acupuncture channels. Qie refers to the process of feeling. Kuriyama (1999) interprets the term qiemai as referring to ‘streams of blood’ (p. 51). In CM, the term pulse diagnosis primarily refers to palpation of the radial arteries at both the left and right arms. It also includes Nine Continent pulses, a seldom—used system that involves palpating several arterial sites situated throughout the body, including the head, torso and legs. In contemporary CM practice, pulse diagnosis is believed to provide both specific and general clinical information (Maciocia 2004):

A wide range of views regarding the importance of pulse in clinical practice is expressed by various authors. Contrary to the emphasis placed on pulse in the diagnostic process by some modern CM authors (Hammer 2001, Maciocia 2004, Porkert 1983), its importance in the modern CM clinic appears to be changing. Some practitioners regularly take the patient’s pulse throughout the treatment session when administering acupuncture in order to gauge the effect of treatment on the patient, and this will influence the duration of needling, the points needled and the degree of needle manipulation. In this case, treatment would continue until the pulse characteristics presented in a desired formation (Birch & Felt 1999). For other practitioners, the pulse is relegated to playing a ‘minor, confirmatory role’ (Flaws 1997: p. 7).

In the experience of two modern CM authors (Flaws 1997, Hammer 1993), the use of pulse as a diagnostic skill has been declining worldwide and particularly in China. In Flaws’ experience as a student in China as long ago as the 1980s, the pulse was examined only briefly, utilising fewer than 10 of the basic CM qualities, such as slow, fast or deep, and rarely discussed in terms of pulse positions. In his opinion, the low importance placed on the pulse in the diagnostic process appeared to stem from the fact that pulse was unable to be validated from a Western physiological perspective, at a time when the focus appeared to be on scientific validation of CM theories.

The changing role of pulse diagnosis was also evident in the results of a questionnaire completed by a selection of Australian university CM students, which evaluated the use of pulse diagnosis by student practitioners (Smith 1996). The study found that while 82% of the students surveyed rated the pulse as ‘important’ or ‘very important’ in formulating a diagnosis, in practice they often used pulse solely as a confirmatory tool and not to establish diagnosis.

In spite of this apparent change in the role of pulse diagnosis observed in students, an Australian survey of CM practitioners found that traditional diagnostic methods are seemingly still being utilised in clinical practice. In 1996 the Victoria State Department of Human Services commissioned a review of the practice of CM in Australia, resulting in a published report called Towards a Safer Choice (Bensoussan & Myers 1996). The authors noted that in a survey of both non-medical and medical practitioners who use CM, 90% of those practitioners who identified CM as their major form of practice said that they relied mainly on CM theory for diagnostic purposes.

Therefore, it can be seen that, amongst the numerous practitioners who utilise CM, there seem to be wide ranging differences in the emphasis placed on the use of traditional theory, such as pulse or tongue diagnosis, in clinical practice. The duration of CM education appears to play some role in determining the importance that allied health practitioners (who incorporated CM practices such as acupuncture into their treatments) give to the traditional theoretical framework. A survey of physiotherapists in the United Kingdom who utilised acupuncture found that: