A device (22) for analgesic immobilization in the event of thorax or rib fractures as well as a method for application of such a device are disclosed. The immobilization device (22) includes a flat splint element (24) which covers a large area of the region of the break (19), and is provided with an adhesive layer (26) which is located on the side thereof facing the body and is used to adhere the immobilization device (22) to the body. In a preferred method of application, two separate areas of adhesive are applied to the patient's skin over the fracture at two different points in the breathing cycle. This allows the device to remain in place more securely under the dynamic condition of the ribcage that results from constant inhalation and exhalation.