Excessive bleeding during hemothorax is caused by

Massive Hemothorax: Collection of more than 1500 ml of blood in the pleural cavity is called massive hemothorax. Massive hemothorax is usually the result of major pulmonary vascular injuries or major aerial wounds, while minor lung injuries cause small hemothorax. Also know Most common cause of hemothorax is due to injuries of Internal mammary Aery. Ref : Sabiston 18/e p498