The mechanism of injury is determined by the External Cause of Injury Codes (HCUP variables ECODEn) and is consistent with the classification system used by the Centers for Disease Control and Prevention (CDC) and documented at http://www.cdc.gov/injury/wisqars/ecode_matrix.html. HCUP includes 11 data elements that identify the mechanism of the injury: cutting/piercing, drowning, falling, fire, firearm, machinery, motor vehicle traffic, natural/environmental, poisoning, suffocation, and being struck by or against. HCUP also includes three data elements that identify the intent of the injury: unintentional, assault, and self-harm. If multiple injuries are reported, more than one mechanism and intent may be identified.