Primary blast injury: an intact tympanic membrane does not indicate the lack of a pulmonary blast injury.

The tympanic membrane (TM) has long been viewed as an indicator of primary blast injury. A primary blast injury occurs due overpressure occurring as a result of the detonation of high explosives. Cadaver studies indicated pressure required for perforation of the tympanic membrane to be 137 kPa for adults. The accepted range in which other organs (lung, colon, and intestines) are damaged by the pressure wave emanating from an explosion is in the 400-kPa range. The use of the perforation of the tympanic membrane as an indicator of a primary blast injury missed a range of up to 50% of those suffering a primary blast injury to the lung. The status of the tympanic membrane following exposure to a blast does not preclude the need for further investigations for a primary blast injury and the clinician needs to evaluate the patient dependent on their particular exposure to an explosion.