The deep pulse (沉脉, Chen Mai) has two meanings, similar to the floating pulse (浮脉, Fu Mai): one is a conceptual location. Any pulse that can only be felt by pressing down to the bones, regardless of its size, speed, strength, or weakness, is termed deep; the other refers to the deep pulse as a specific type of pulse with strict characteristics. To distinguish between the two, the former can be called “pulse deep” (脉沉), while the latter can be referred to as “deep pulse” (沉脉).
A normal deep pulse is characterized by being insufficient when lifted and excessive when pressed, resembling sand wrapped in cotton, firm inside and soft outside. In addition to being located deep and requiring heavy pressure to reach the bones, it must also possess the characteristics of being “soft, slippery, and even.” Soft and even indicate a relaxed appearance within the deep pulse, with a smooth and even flow, reflecting the presence of stomach qi (胃气, Wei Qi). The deep and slippery pulse indicates the yin aspect (阴) of the pulse, while the slippery aspect (滑) represents the yang, symbolizing yang submerged in water, which corresponds to the pulse of winter and the kidneys (肾, Shen).
The deep pulse is a very important pulse because the pulse is fundamentally based on the deep aspect. The pulse is governed by the concepts of deficiency and excess, and the distinction between deficiency and excess lies in the strength or weakness of the deep pulse. Therefore, the deep pulse is extremely significant.
Why is the pulse deep? It is because the qi and blood cannot express outwardly to invigorate and fill the blood vessels, resulting in a deep pulse.
Why can qi and blood not express outwardly? There are two main reasons: one is the deficiency of righteous qi (正气, Zheng Qi), leading to the inability of qi and blood to express outwardly, resulting in a deep pulse; the other is the obstruction of pathogenic qi (邪气, Xie Qi), which blocks the pathway for qi and blood to express outwardly, also leading to a deep pulse.
1. Deficiency leading to a deep pulse
A deep pulse due to deficiency can be seen in conditions of yang deficiency (阳虚), qi deficiency (气虚), blood deficiency (血虚), and yin deficiency (阴虚). Yang is active and can stimulate and invigorate the functions of the entire body. When yang is deficient, it cannot effectively stimulate the circulation of qi and blood, resulting in a deep pulse. Qi acts as a bellows, invigorating the blood vessels. When qi is deficient, it cannot invigorate, hence the pulse is deep. In cases of blood deficiency, there is insufficient filling of the blood vessels, leading to a deep pulse. Moreover, blood deficiency often accompanies qi deficiency, resulting in both qi and blood being insufficient, causing the pulse to lose its fullness and vigor, thus becoming deep. In cases of yin deficiency, the blood vessels also fail to be filled, leading to a deep pulse. When there is deficiency, the pulse is deep and weak.
When encountering a deep and weak pulse in clinical practice, the nature of the illness is undoubtedly one of deficiency. However, determining whether it is yang deficiency, qi deficiency, blood deficiency, or yin deficiency requires a comprehensive analysis based on the accompanying pulses and the three diagnostic methods of observation, listening, and inquiry.
In cases of yang deficiency, the pulse is deep, slow, and weak, accompanied by symptoms of cold limbs, pale tongue, and slippery coating indicative of cold. In cases of qi deficiency, the pulse is deep and weak, accompanied by shortness of breath and weakness. In cases of blood deficiency, the pulse is deep, thin, and weak, accompanied by a pale complexion, palpitations, and a pale, tender tongue. In cases of yin deficiency, the pulse is deep, thin, and rapid, accompanied by symptoms of deficiency heat and a red tongue with little coating.
In the previous lesson on the floating pulse, we mentioned that deficiency can lead to a floating pulse, and here we say that deficiency can also lead to a deep pulse. Is this not contradictory? Not at all. A deficiency pulse can be either deep or floating, depending on the degree and nature of the deficiency. In cases of yang deficiency, if the deficiency is not severe, the pulse can be deep and weak; however, if yang deficiency leads to a rejection of yin and yang, causing yang qi to escape outward, the pulse can change from deep and weak to floating, large, rapid, or scattered. If yang deficiency worsens further, even the ability to float is lost, and the pulse can change from floating and large to deep and thin, or even absent. In cases of mild qi deficiency, the pulse may not withstand heavy pressure or may feel weak upon pressure. If qi deficiency is accompanied by internal heat, the qi and blood may float outward due to the pressure of the internal heat, resulting in a large, rapid pulse. In cases of extreme qi deficiency, the pulse may float and scatter, or it may become deep and thin, nearly absent. Since blood is the mother of qi, blood deficiency often accompanies varying degrees of qi deficiency. When both qi and blood are insufficient, they cannot invigorate the blood vessels, resulting in a deep, thin, and weak pulse. If blood deficiency cannot retain the qi, the qi will float outward, leading to a large, weak pulse. Especially when blood is violently lost, the qi will escape outward, resulting in a large, hollow pulse. In cases of yin deficiency, if yang qi has not yet floated outward, the pulse is often deep, thin, and rapid. If yin deficiency is more severe, and yin fails to restrain yang, leading to yang floating outward, the pulse may become floating, large, and rapid, or yin may be exhausted below while yang rises above, presenting a pulse of strong yang and weak yin. Therefore, even with deficiency, the pulse can be deep or floating, depending on the degree and nature of the deficiency.
2. Obstruction leading to a deep pulse
Internal and external pathogenic factors can obstruct the outward expression of qi and blood, leading to a deep pulse, including the six excesses (六淫, Liu Yin), seven emotions (七情, Qi Qing), and issues with qi, blood, phlegm, food, etc.
1. The six excesses can lead to a deep pulse. It is commonly said that a floating pulse indicates an exterior condition, and a floating pulse is typical for exterior syndromes. However, upon careful observation in clinical practice, it is often found that at the onset of an exterior condition, many pulses are not floating, but rather deep. Indeed, individuals with deficient righteous qi may have a pulse that is not floating; however, even robust individuals may not have a floating pulse at the onset of an exterior condition. The reason for this is due to the obstruction caused by pathogenic qi.
When a cold pathogen invades the surface, its nature is to condense and obstruct, closing the pores and blocking the meridians, preventing qi and blood from expressing outwardly, hence the pulse is not only not floating but appears deep. As stated in the “Four Diagnostic Methods” (四诊抉微, Si Zhen Jue Wei): “When there is severe exterior cold, yang qi cannot express outwardly, and the pulse must first be seen as deep and tight.” It is also stated: “Is it possible for cold to close the pores, causing both nutritive and defensive qi to be obstructed, and the pulse to not be seen as deep?”
In the early stages of a new warm disease, when the pathogen invades the lung and defensive qi, the pulse should be floating. Since the warm pathogen is a yang pathogen, it is active and invades the defensive level, the pulse should be floating. However, in clinical practice, it is often found that at the onset of a warm disease, the pulse is also often deep. Why is the pulse deep at the onset of a warm disease? Because the warm pathogen first affects the lung, causing lung qi to be obstructed.
Stagnation leads to an obstruction of qi flow. The warm pathogen accumulates in the lung, creating heat, and the defensive yang fails to express, leading to aversion to cold, and qi and blood cannot express outwardly, resulting in a deep pulse. Thus, even at the onset of a warm disease, a deep pulse is understandable. This indicates that the deep pulse can also indicate an exterior condition.
Of course, it is not that exterior conditions do not present with a floating pulse. When the external pathogen transforms into heat, the heat accumulates and extends, invigorating qi and blood to express outwardly, and the pulse becomes floating. If the heat becomes further excessive, qi and blood may be forced outward by the heat, resulting in a pulse that is not only floating but also large and rapid. At this point, the condition has progressed from the taiyang (太阳, Tai Yang) stage to the yangming (阳明, Yang Ming) stage, or from the defensive level to the qi level.
While it seems that the floating pulse is an unchanging conclusion for exterior conditions, the presence or absence of a floating pulse has become a major criterion for determining exterior conditions. However, through the above discussion, it is clear that at the onset of an exterior condition, the pulse may not be floating. So how should we determine the presence of an exterior condition? The main indicator for determining the presence of an exterior condition should be the presence of aversion to wind and cold. The presence of even a slight aversion to cold indicates an exterior condition. Of course, both heat accumulation and yang deficiency can cause aversion to cold, but they differ from the aversion to wind and cold seen in exterior conditions. The aversion to wind and cold in exterior conditions must meet the following characteristics: first, there is aversion to wind and cold at the onset of the disease; second, aversion to cold and fever occur simultaneously; third, if the exterior condition does not resolve, the aversion to wind and cold will not disappear; fourth, aversion to cold and fever occur simultaneously, accompanied by symptoms such as body aches, nasal congestion, and cough. If these characteristics of aversion to wind and cold are present, then an exterior condition exists; if these characteristics are absent, then no exterior condition exists. Therefore, the presence or absence of an exterior condition should not be based solely on whether the pulse is floating or deep.
2. Emotional disturbances can lead to a deep pulse. Emotional disturbances disrupt the flow of qi, preventing qi and blood from circulating smoothly, resulting in a deep pulse. Within a deep pulse, there may also be characteristics of fullness, wiry, thin, rough, slow, knotty, etc. The appearance of these different pulse qualities reflects the same pathological mechanism, all due to qi stagnation, preventing the smooth flow of qi and blood. Due to varying degrees of stagnation, the strength of the righteous qi varies, leading to the appearance of different qualities such as fullness, wiry, thin, rough, slow, etc.
3. Phlegm, dampness, stasis, food stagnation, water accumulation, masses, fullness of the bowels, and heat stagnation can all obstruct the flow of qi, leading to a deep pulse. Due to the different types of obstructive pathogenic factors, the degree of obstruction varies, and the deep pulse may also present with slippery, wiry, thin, soft, rough, full, knotty, or even hidden or absent qualities. Since all these are due to pathogenic excess, they all present as deep and strong.
