Tanzhong or Shanzhong, which can be translated as 'chest center'.
It is the meeting point of Qi energy.
It's the Mu point of the Pericardium.
It is also the crossing point of the Small Intestine, the Spleen, the Kidney and the Triple Burner.
Location of Tanzhong
Tanzhong is located midway between the 2 nipples, in the 4th intercostal space, on the sternum.

Book - Meridians and acupuncture points
Illustrated book: 183 points
Therapeutic functions and clinical indications of Tanzhong
- Tanzhong is the meeting point of energy, to be used whenever there is a Qi problem of any kind ;
- It is a very useful local point for regulating respiratory problems and chest pain, breast, lung or heart pain ;
Important point to regulate the Qi mechanism, one point is taken above Tanzhong and one below Qihai.