An upper airway obstruction (blockage) occurs when a piece of food or some other object enters the person's trachea (windpipe). When a person has suffered a facial injury, blockage may be caused by blood clots or loose teeth that have become lodged in the person's throat. Blockage may also occur when the contents of the stomach are regurgitated (vomited) and some of the vomitus is inhaled.

The blockage must be removed and full breathing restored. A blockage which greatly reduces the amount of air which can be inhaled and exhaled or which stops all air exchange can quickly lead to unconsciousness and death.