Left subclavian pain with shortness of breath may be caused by injury or inflammation of thoracic tissues, pleural and lung diseases. 1. Thoracic tissue injury or inflammation (1) Local tissue contusion or infection: local tissue contusion caused by external force, or local tissue infection with bacteria, etc., will cause pain, edema, redness and heat below the left clavicle, and shortness of breath due to the pain that will lead to respiratory depression. (2) Fracture or fracture of the clavicle: Fracture or fracture of the clavicle caused by trauma or disease. It will cause pain when the thorax is pulled, leading to pain and shortness of breath. 2. Pleural and Lung Diseases (1) Spontaneous pneumothorax: For the elderly or emaciated, excessive activity may lead to pneumothorax, which manifests itself as sudden chest pain and may be accompanied by shortness of breath or dyspnea. (2) Lung and pleural tuberculosis: the apical region of the lungs is a high incidence area of tuberculosis, after the occurrence of tuberculosis of lung tissues or pleura in the apical region of the lungs, chest pain, shortness of breath and other manifestations, as well as fever, night sweats (sweating abnormally after going to sleep, and sweating stops after waking up), and so on. When shortness of breath occurs with pain below the left side of the clavicle, it is recommended to go to the hospital in time.