The Kidney's Relationship With The Lungs
According to the five elements theory, the relationship between the kidneys and the lungs is like a bond between a mother and child. The kidneys belong to water element and the lungs belong to metal element; the metal and water elements mutually generate and support each other. They depend on each other physiologically, and influence each other pathologically. The lungs are the respiratory organs. By inhaling clear qi from natural air and exhaling turbid qi out of the body, it exchanges the qi between the interior and the exterior of the body. Depending on the regulation of lungs, qi (vital energy) can circulate smoothly throughout the body, and therefore, a normal state of internal metabolism is ensured. However, respiration does not merely depend on the lungs alone; the kidneys also coordinate it. In order to keep the qi exchange effectively, the inhaled and refined qi must flow down and be grasped by the kidneys properly. The astringent or grasping and holding function of the kidneys ensures the lungs to receive and circulate downward the qi. In this way, the former helps coordinate respiration while the latter controls respiration.
Normal respiration depends on mutual regulation by the kidneys and the lungs. The relationship is clearly stated in a famous book, Differential Diagnosis and Treatment of Diseases (lei zheng zhi cai): "the lungs are the master of qi and the kidneys are the root of qi; the lungs dominate exhaling qi and the kidneys grasp inhaling qi; a coordinated work between them, respiratory movement will be harmonized." Physiologically, the kidney-qi must be strong and their astringent, grasping and holding functions must be sound, in order to have smooth respiration and a clear airway. When a kidney deficiency develops that fails to grasp the qi inhaled by the lungs, then qi cannot flow deep inside the body. This can lead to respiratory problems like difficulty inhaling with longer exhaling time, and situations will become worse when the body exercise too. TCM calls this the "kidney failing to grasp qi, " or "kidney deficiency with counterflow of qi." Clinically, diseases like severe chronic bronchitis, emphysema and pulmonary heart problems (problems affecting the right side of heart) are all due to the kind of kidney disharmony.
