### Literature Review
#### Injury Severity and Trauma Scoring for Prediction of Survival Based on Physiological Parameters
The survival prediction power of TRISS could be substantially improved by re-classifying the measured physiological parameters and altering the coefficients for the environmental conditions, the demographics or the situations (e.g., combat). Despite some variations in the scoring mechanism in TRISS, due to the influence of demographics and environmental conditions on the patients, it remains a widely used model. Anatomic injury, age, injury mechanism, and pre-injury comorbidity are well-founded predictors of trauma outcome and for calculating the TRISS score. Statistical prediction models may have some inaccuracies, though these may be due to inaccurate calibration and inaccuracy due to applications of these models with influence on the environmental conditions [12]. Early warning scores have largely been used in cardiac emergencies, as these patients, along with other fatal injuries, require medical attention and lead to the emergent incident response [15]. Recognizing the early signs of clinical deterioration of patients is thought to improve patient treatment outcomes. The Early Warning System (EWS) scores and the impact of EWS outcomes were studied on the 48 hr mortality rate for respiratory failure and cardiac arrest patients. It was found that the early warning system scores performed well for predicting cardiac arrest and death within 48 hr. For ailments like cardiac arrests, early warning scoring mechanisms become relevant and applicable as these patients may enter trauma at any time, and healthcare service providers need to prepare ahead of time with readiness to attend to this trauma [23]. For patients admitted to ICU and facing deterioration of health, physiological parameters such as pulse rate, blood pressure, temperature, and respiratory rate could be used to assess mortality, and serious adverse events (SAEs) such as cardiac arrest could be prevented. The EWS is a scoring system which assists with the detection of physiological changes, and it may help to identify patients who are at risk of further deterioration [24]. In cardiac ailments, reduced heart rate (HR) is an established predictor of trauma and further mortality. However, the relationship between the predictors and trauma scoring is poorly understood, hence it becomes important to establish the relationship between heart rate variability and trauma scores [13; 25; 26]. The importance of using injury severity, comorbidity, and prediction-of-survival scores becomes paramount in military operations when troops who engaged in combat may require medical attention. The situation aggravates when the location of the troops is not known and a soldier requires medical attention, if the time frame of the arrival to the base camp is uncertain. In such cases, predicting survival and the measures related to injury severity scores become very important, and the wearable vital signs and physiological measurement kits that can calculate and perform further analysis become a very crucial instrument [13]. The TRISS methodology has been used in both the UK and US Military trauma registries. The method relies on dividing the casualties according to their survival probability (penetrating (Ps_penetrating) or blunt (Ps_blunt)), though the use different weighing mechanisms based on experiences in combat-related environments. The UK Military Joint Theatre Trauma Registry (JTTR) and the US Military use the same scoring mechanism with some variations in coefficients for soldiers who have been injured in explosions. This study aimed to use the UK Military JTTR to calculate new TRISS coefficients for contemporary battlefield casualties who were injured by either gunshot or explosive mechanisms. The secondary aim of this study was to apply the revised TRISS coefficients to examine the survival trends of UK casualties from recent military conflicts. Such systems and early warning scoring kits can be very useful to forces who are deployed in combat zones where the scores can be calculated in real time in the event of an emergency [27; 28].