Normally after choking the foreign body will be retained in the trachea and will not enter the lungs, but there are some special cases. Whether the foreign body chokes into the trachea or lungs can be judged by clinical manifestations and imaging examinations, bronchoscopy and so on. 1. Clinical manifestations: after choking on a foreign body into the trachea, there will be a violent cough. Cough a few times or a dozen times each time, each cough is not continuous, coughing will stop after coughing out the foreign body. If the foreign body is large and cannot be discharged in time, dyspnea will also occur. Foreign body choking into the lungs usually does not appear after the severe irritation of coughing, may be because of the foreign body triggered by infection and fever, coughing up sputum and so on. 2. Imaging examination: this can be through the chest X-ray, chest ct, etc. to check the metal foreign body. 3. Bronchoscopy can not only find out whether there is a foreign body in the trachea or lungs, but also remove the foreign body through bronchoscopy. After choking on a foreign body, you should immediately use the Heimlich maneuver, which will help the patient cough up the foreign body as soon as possible. If the foreign body can not be coughed out need to go to the hospital immediately for treatment, so as to avoid life-threatening.