The interaction of a blast wave with the thorax produces primary pulmonary blast injury by releasing energy at biological interfaces of differing acoustic impedance. This process is known as coupling. It was hypothesised that protective armour designed on the basis of an acoustic decoupler, may modulate the effect of thoracic blast.

Anaesthetised, spontaneously breathing male pigs (n=18) were allocated into two equal groups and exposed to whole body blast in free field conditions. All animals were provided with Kevlar® protection, but in addition animals in group 2 were provided with protective thoracic armour. Blood gas analysis was performed prior to and up to 1 h post-blast. The animals were killed at 1 h post-blast and a post-mortem carried out. Severity of lung injury, called the quotient of injury (QI) was calculated by comparing masses of injured lung with standardised uninjured lung masses.

All procedures complied with the Animals (Scientific Procedures) Act 1986.

In group 1, PaO2 was reduced from a pre-blast mean of 9.7 kPa to a post-blast mean of 6.6 kPa, whereas in group 2 PaO2 fell from a pre-blast mean of 10.5 kPa to a post-blast mean of 8.3 kPa. The difference between the groups was statistically significant (p< 0.05). The mean QI in group 1 was 1.7 compared to a group 2 mean of 1.12, indicating severe injury in the unprotected animals (p< 0.01).

Decoupling protective thoracic armour ameliorated the effects of thoracic blast in this animal model. This will lead to the development of personal protective thoracic armour for frontline servicemen.