Signs and symptoms vary depending on what part of the tracheobronchial tree is injured and how severely it is damaged.[6] There are no direct signs of TBI, but certain signs suggest the injury and raise a clinician's suspicion that it has occurred.[16] Many of the signs and symptoms are also present in injuries with similar injury mechanisms such as pneumothorax.[17] Dyspnea and respiratory distress are found in 76–100% of people with TBI, and coughing up blood has been found in up to 25%.[14] However, isolated TBI does not usually cause profuse bleeding; if such bleeding is observed it is likely to be due to another injury such as a ruptured large blood vessel.[2] The patient may exhibit dysphonia or have diminished breath sounds, and rapid breathing is common.[3] Coughing may be present,[18] and stridor, an abnormal, high-pitched breath sound indicating obstruction of the upper airway can also occur.[19]