The heart and lung

The heart dominates blood and the lung dominates qi. The circulation of blood relies on the propelling function of qi, and at the same time the qi is attached to the blood to distribute it through the body. Both the heart and the lung, qi and blood, rely upon each other. Without qi, the blood will stagnate, leading to stagnation of blood ; without blood, the qi will have base to rely upon and will scatter.

Pathologically, deficiency of pectoral qi due to weakness of the lung qi will lead to weakness and stagnation of blood circulation, resulting in stuffiness in the chest, shortness of breath, palpitation, and purplish lips and tongue. Conversely, retardation of blood circulation due to deficiency of heart qi or weakness of heart yang may impair the function of the lung in dispersing and descending, giving rise to cough, shortness of breath, stuffiness in the chest and a sensation of suffocation.

Both the heart and lung are situated in the upper jiao. During the development of febrile diseases, the pathogenic factors in the lung may not be transmitted to the middle jiao by the normal pathway, but invade the heart directly. This is known as " invasion of the pericardium by pathogenic factors through contrary pathway, " showing the mutual connection between heart and lung in pathology