## 3 Design Specification
### Medical Considerations and Research  
As mentioned in the introduction, one of the main priorities in casualty extraction procedures is to ensure minimal harm or risk. One of the main design considerations is to minimise any possible traumatic injuries during the casualty extraction procedure. Any unfavourable handling might aggravate injuries, particularly to the neck, head, and spinal cord (which includes the cervical spine). For this reason, medical professionals were consulted during all design stages of ResQbot 2.0, and a survey of the literature was carried out [48; 49; 50; 51; 52; 53; 54; 55; 56; 57].  
According to our literature review, it was found that spinal cord injuries and unstable fractures are some of the major concerns. Such injuries can occur either at the tetraplegic (the neck region) or paraplegic level (lower back region) [48; 49; 51; 52; 53; 54; 55; 56; 57]. Injuries at the tetraplegic level can cause impairment or loss of motor or sensory functions in the cervical segments of the spinal cord, affecting arms and legs [48]. To avoid this type of injury, any additional backward (hyperextension) or forward (hyperflexion) bending of the neck, as well as compression or rotation must be avoided [48]. To prevent potential paraplegic traumas, any forward or backward bending of the lower back must also be avoided, although this is less critical.  
Possible existing injuries must be taken into account when performing a casualty extraction, especially the possibility of secondary spinal cord injuries, including neurogenic shocks, post-traumatic ischemia or failure to stabilise and immobilise an unstable fracture, which might cause bone fragments to move towards, put pressure on or cut the spinal cord [48]. One of the standard operating procedures is to place the cervical spine in a neutral position and attach a stabilisation unit to the patient, as proposed in [30]. The main objective of this procedure is to minimise translation and rotation of the head in order to avoid the aggravation of spinal injuries during lifting or transportation. In classical ambulant care, post-trauma stabilisation usually includes fitting a cervical collar to the patient's neck as a frame to immobilise the head. However, recent work has illustrated that a cervical collar is not indispensable, and might even restrict a patient's airway [50; 51]. Therefore, cranio-thoracic stabilisation methods, such as sandbags or stabilisation blocks that maintain the cervical spine straight without a cervical collar [52; 53], have received increased attention.  
Another safety consideration related to casualty extraction procedures, as shown in Figures 2b and 3b, is the possibility of head injury during contact between the robot and the casualty's head. A number of research studies have focused on evaluating and developing methods and technical devices that could protect against both spinal cord and head injuries [43; 44]. In [43], [PERSON] presents an investigation into the possible spinal cord and head injuries caused by an impacting force. This study evaluates several impact-testing methods as well as a selection of injury threshold limits. In a separate study, EURailSafe [44] presented a report on the evaluation of bot head and neck injuries,including injury mechanisms, criteria, and tolerance levels. We used the data from [43; 44] to obtain the key safety thresholds and validate our design results.