Pain inside the left chest that hurts when you gasp for breath may be caused by trauma, pleurisy, acute coronary syndrome, etc. 1. Trauma: Trauma to the left side of the chest, especially when combined with a rib fracture, may lead to pain in the left side of the chest and pain when breathing. 2. Pleurisy: Pleurisy refers to inflammation of the thin layer of tissue covering the lungs and chest wall, and the inflammation stimulates the pleura, leading to pain in the left chest and pain when breathing. 3. Acute Coronary Syndrome: Acute thrombosis of the coronary arteries due to severe stenosis or spasm of the coronary arteries supplying blood to the heart and rupture of atherosclerotic plaques in the blood vessels leads to the development of acute thrombosis in the coronary arteries, resulting in pain in the left chest when you gasp for breath. The left chest pain in the left chest pain with a gasp, the patient should go to the regular hospital in time, clear cause, under the guidance of professional doctors to give targeted treatment.