Lung Yin deficiency fèi yīn xū · 肺阴虚

Lung yin deficiency is the pattern name used when the moistening and cooling aspect attributed to the lung is described as depleted. Yin is the quieter, cooler, more material aspect; deficiency of it leaves a picture of dryness together with low-grade heat.

The recorded features are: a dry cough with little sputum, or sputum that is scanty, sticky and difficult to bring up; a dry mouth and throat; a hoarse voice; feverishness in the afternoon or evening; night sweating; a sense of heat in the chest, palms and soles; loss of weight; a red tongue with little coating or with cracks; and a fine, rapid pulse. The classical texts attribute the picture to prolonged coughing, to consumption-like illness, to the aftermath of a febrile disease, and to dryness.

Blood in the sputum is the line this library does not walk around. Any amount is assessed, and no pattern name makes it less urgent. A cough lasting more than three weeks, weight loss, night sweating, fever, or hoarseness lasting more than three weeks are also reasons for imaging and investigation rather than for interpretation: tuberculosis and lung cancer both live in this symptom space, and tuberculosis keeps transmitting while it is undiagnosed.

The same chronic cough can come from asthma, reflux, an ACE inhibitor, post-nasal drip, bronchiectasis or interstitial lung disease. The ACE inhibitor example is worth pausing on: in many people the cough stops when the medicine is stopped, which is a matter of prescribing rather than of yin.

Whether the moistening methods recorded for this pattern change any outcome has not been established. The identification of classical consumption with tuberculosis was made long after the texts were written; those texts contain no concept of the organism.