Military thoracic gunshot wounds: A systematic review

Body armour designs have changed significantly over the last 80 years from 1 mm thick manganese steel chest plates issued to Airborne forces in WW2, to M1952 flak jackets in Korea, followed by the M-69 Fragmentation Protective Body Armour in Vietnam and were continued to be worn during the start of the troubles in Northern Ireland (Tobin and Iremonger 2006; Carr and Lewis 2014). The M1952 and M-69 flak jackets did provide a certain level of protection against fragmentation and shrapnel; however, this level did not encompass protection against high-velocity projectiles, and therefore the frequency of thoracic gunshot injuries and the percentage of fatalities from thoracic GSW continued to remain high.

In 1965 para-aramid fibres were discovered and in 1972 they were commercialised by Dupont as Kevlar and were seen to offer ballistic protection from handguns. Para-aramids are still used in both military and police body armours today.

In the late 1970s the UK Forces were issued with Individual Northern Ireland Body Armour (INIBA), which not only offered protection from fragmentation and shrapnel but also protection against high-velocity projectiles using front and rear hard ceramic plates (Breeze et al. 2021). This would have led to reduction in the number of thoracic GSW and subsequent fatalities.

Meanwhile, the US military issued the Personal Armor System for Ground Troops (PASGT), which remained in service till the early 2000s. PASGT was designed to provide better protection against fragmentation and saw the move away from ballistic nylon to Kevlar by the US military (Roberts and Bullian 1993).

In 1991, the First Gulf War (GW1) saw Enhanced Combat Body Armour (ECBA) issued to UK Forces, which incorporated two ceramic hard armour plates with soft body armour (Carr and Lewis 2014). GW1 saw the widespread use of body armour for the first time with ECBA and PASGT being worn. (Brayley 2011).

In 2003 the US military issued Interceptor body armour (IBA), which consisted of an outer tactical vest that provided protection against fragmentation and handgun bullets, whilst the two Small Arms Protective Inserts (SAPI plates) provided protection up to 7.62 mm Full Metal Jacket (FMJ) bullets (Brayley 2011). The UK Forces continued to wear ECBA until 2006 and the introduction of OSPREY. The OSPREY plates provided better coverage and higher performance than the ECBA plates and provided an enhanced multi-hit capability, and the ECBA plates were repurposed as side plates to increase coverage area (Carr and Lewis 2014, Breeze et al. 2017). This protection from high-velocity bullets would have certainly led to a decrease in the number of thoracic GSW, as a large percentage of bullet threats seen in combat theatres were defeated.

The US forces issued the Improved Outer Tactical Vest (IOTV) in 2007, which saw enhanced SAPI (ESAPI) plates made from boron carbide that covers critical areas of the torso and provides protection from armour-piercing ammunition, and also features enhanced side ballistic inserts (ESBI) (Brayley 2011).

In 2016 the UK forces were issued VIRTUS scalable tactical vests, which allow the user to scale their protection level depending on the threat. They can be worn in several configurations including no armour, soft armour made of composite granular materials or a full armour system comprising of soft armour and hard ballistic plates (Lewis and Clarke 2018).

The original flak jacket fielding in Korea and Vietnam protected the thorax and the abdomen; however, during the 1970s it was recognised that some anatomical structures are more susceptible than others. This led to changes in design to provide the more susceptible anatomic structures extra protection. The soft armour continues to cover the whole thorax and abdomen as it is primarily designed to protect against fragmentation. The INIBA and ECBA plates covered the heart and mediastinum and were developed based on the prevalent threat and favourable condition of medical attention being available within 20 min during the Northern Ireland conflict. The ceramic plates used in the OSPREY system were refined based on the time to medical care being 1–2 h, and in addition to the heart and the mediastinum, also protected the spleen and the liver (Breeze et al. 2016a,b).

ECBA plates have been used in OSPREY and VIRTUS to provide side protection and have been shown to already be optimised to provide side protection despite not being designed for this purpose (Breeze et al. 2021). It has also been recommended that a range of plate sizes should be used to optimise the coverage and effectiveness of body amour (Breeze et al. 2016a,b).

SAPI plates come in five sizes (extra-small to extra-large) designed to optimise fit and comfort for the user whilst providing suitable coverage for a range of body sizes and shapes.

More recently Breeze et al. have defined the essential coverage areas whose structures are likely to result in death within 60 min of significant injury unless damage control surgery (DCS) is received. These areas are defined as ‘Heart, Mediastinal great vessels, Superior vena cava, Inferior vena cava, Pulmonary arteries and veins, Aorta, Brachiocephalic artery and veins, Left common carotid artery, Subclavian artery and vein, Iliac arteries and veins, Liver, Spleen, and Intrathoracic trachea’ (Breeze et al. 2020).

Body armour standards were introduced by the National Institute of Justice in 1972 with other standards such as the NATO Allied Engineering Publication 2920 also being developed over time. The purpose of the standards is to ensure that body armours offer an adequate level of protection against the threats that are tested. This not only ensures that high-velocity bullets are stopped but also that back face deformation of the body armour does not cause excessive blunt force trauma (Carr and Lewis 2014).

Military body armour is procured in accordance with the relevant national authority threats and specifications and therefore this ensures that the most common rounds in combat theatres are defeated and consequentially the number of thoracic GSW and subsequent fatalities are reduced.

During WW2, due to the complexities of evacuation and the sheer volume of casualties it could take between 12 h and 15 h for a casualty to be triaged and provided the necessary care. Based on the experiences of WW2, a Mobile Army Surgical Hospital (MASH) was put in place by the US Army for the Korean War. The MASH provided resuscitative surgical care within 10 miles of the front line and was supported by helicopter ambulances allowing casualties to be treated in 3–12 h of wounding and subsequently the mortality rates of all injuries were reduced. The use of helicopters in the medical evacuation was continued during the Vietnam War and the process improved. The helicopters transported casualties directly to full-service hospitals and reduced the treatment time to 60 min and ensured that treatment was provided within what is considered the golden hour (Manring et al. 2009).

Due to the changes in warfare, MASH hospitals were shown to be unsuitable during the GW1. This led to the formation of Combat Support Hospitals (CSH), with the new CSH first being used in 2003 in Iraq, and more recently the US has used a system that involves five levels of care, ranging from battalion aid stations to stateside trauma centres and a medical response time of 30–90 min (Manring et al. 2009).

Casualty evaluation timelines of UK forces are based on the NATO Allied Joint Publication (AJP) 4–10: Allied Joint Doctrine for Medical Support. The first version published in 2006 stated that battlefield advanced trauma and resuscitation techniques occur within 1 h, DCS within 2 h and any further surgical procedures within 4 h (1–2–4 principle). An update to medical timelines was published in 2010, and called for first aid within 10 min, skilled medical aid in 1 h and DCS in 2 h. This was formalised in the 2015 update of the AJP 4–10 and became known as the 10–1–2 principle. However, the UK followed 10–1–2(2) +2, where the (2) is time taken to deliver DCS and the +2 is evacuation to deployed hospital care (DHC) for in-theatre surgery. The AJP 4–10 was updated in 2019 to follow these time frames but the +2 refers to further surgical, diagnostic, specialist care etc. being made within 2 h of tactical evacuation after DCS (Scallan et al. 2020).

The Medical Emergency Response Team (MERT) was formed due to the lack of secure road routes in Iraq and Afghanistan and allows medical interventions to be delivered that would normally be restricted to hospital facilities and can also be attributed to the decrease in fatalities (Keene et al. 2017).

Improvements in medical techniques are wide-ranging but the key improvements have come in the form of infection treatment, haemostatic resuscitation and thoracic wound treatment.

Penicillin was first discovered in 1928 by Alexander Fleming, but it was not successfully used as a treatment to treat infections until 1942. The first large-scale use of it was not carried out until the D-Day invasions in 1944 and the Korean and Vietnam wars saw penicillin used in conjunction with streptomycin. The treatment of infection would have led to a reduction in the number of fatalities of thoracic GSW, but it was likely that during these conflicts many fatalities occurred before infection became a contributing factor. This is highlighted by broad-spectrum antibiotics not generally being administered in early treatment during the Iraq and Afghanistan conflicts (Manring et al. 2009).

Whole blood transfusions were introduced in 1944 and military blood programmes were established in 1953. Since the 1980s, whole blood has been separated into packed red blood cells (PRBC), fresh frozen plasma (FFP), platelets and cryoprecipitate. This allows specific components of blood to be administered without the risks of using whole blood and a ratio of 1:1:1 (platelets: FFP: PRBC) has been shown to improve mortality. Once bleeding is controlled, a more tailored approach is used to improve blood volume and pressure. Coagulopathy is assessed and any intervention needed is delivered. Tranexamic acid (TXA) is administered within 3 h and has also been shown to significantly reduce mortality in trauma bleeding casualties (Keene, et al. 2017).

Thoracic wound treatment has evolved from needle aspiration in WW2, to thoracentesis during the Korean and Vietnam wars, to tube thoracotomy in the 1980s, to more modern techniques including using vented chest seals, needle thoracentesis and simple thoracostomy, which has been shown to reduce the risk of pneumothorax (Kotora et al. 2013, Littlejohn 2017) and would have subsequently reduced the number of fatalities.

This study has several limitations. Firstly, the reporting of patients injured varies; for example, Schauer’s study (Schauer et al. 2019) showed a significant increase in the number of casualties presenting at military emergency departments with thoracic GSWs in Iraq and Afghanistan. Hinsley’s study (Hinsley et al. 2005) also showed an increase in the number of casualties presenting to the field hospital in the first 2 weeks of Operation Telic; however, both of these studies may have included unprotected civilian casualties. In contrast, Koshashvilli’s study (Kosashvili et al. 2005) also showed an increase in the frequency of casualties suffering from thoracic GSWs; however, it should be noted that the majority of casualties were only wearing Kevlar body armour, which offers very little protection against high-velocity bullets. Secondly, the format of the data in the sources is varied, ranging from the percentage of all injuries, percentage of thoracic injuries and percentage of GSWs. While some sources provided detailed information, many sources did not. Thirdly, the included studies rarely detailed if body armour was being worn and if so the type of armour, and therefore, it cannot be determined if the development of body armour alone has directly reduced the mortality from these injuries. Fourthly, it is unknown if the studies include fatalities that occurred before treatment could be received, or if injuries that did not require hospital treatment are captured. Lastly, it is difficult to make comparisons between the combat environments because of the way in which information is presented and many studies having an unclear bias; therefore, only broad general observations can be made.

However, despite these limitations, it is clear that GSWs to the thorax remain a credible risk. This review confirms that advancements in body armour have not eliminated the threat of thoracic GSW, which still account for approximately 15% of all thoracic injuries in the most recent combat theatres (Stevenson, Carr et al. 2018, Schauer, Naylor et al. 2019). Thus, roles 1 and 2 medical personnel should be aware of the frequency and severity of thoracic gunshot injuries and should be prepared to treat these life-threatening injuries.

Future systematic review work should include the inclusion of injuries caused by fragmentation due to the change in the nature of warfare and IEDs being a prevalent threat. It should also include sensitivity analysis to determine the effects of including studies with an unclear risk of bias on the overall analysis and observations made.

With the developments of new materials and armour that can protect against armour-piercing ammunition, further research should be carried out to look at the tradeoffs between protection and mobility and how improved operability can subsequently improve survivability.

With the changing face of combat, the traumatic injuries incurred are likely to change; thus, future studies should focus on these changes to optimise the prevention and treatment of casualties.