# Augmented Reality, Mixed Reality, and Hybrid Approach in Healthcare Simulation: A Systematic Review
## 3 Results
### General Features of Simulation Systems (GQ7-9, Fq7-10)
#### 3.8.2 Implementation of Different Levels of Complexity (GQ8)  
To design an effective learning experience in simulation-based medical education, an important factor is the possibility to offer a wide range of task difficulty levels. An appropriate level of training allows the trainee to increase the mastery of skills; the learners have opportunities to engage in the practice of medical skills, starting from basic techniques (novice levels) and proceeding to train at progressively higher difficulties (expert levels) [50]. Five of the 23 articles address question GQ8 (\"Does the simulator allow selection of different scenarios based on trainee's needs?\").  
In [33], the authors propose an AR laparoscopic simulator including a box-trainer, a camera, and a set of laparoscopic tools equipped with custom-made sensors. Sucha system allows the traine to interact with various VR training elements. To this, the authors implement three different training tasks: instrument navigation, to improve the perception of depth of field; peg transfer, for hand-eye coordination skills; and clipping, for bimanual operation.  
In [40], the authors developed an AR simulator (SimPCNL) for percutaneous nephrolithotomy and successively compared it with the commercial virtual simulator, PERC Mentor (Simbionix, Cleveland, OH). Both simulators allow the trainees to practice basic tasks for percutaneous access procedures performed under real-time fluoroscopy on a variety of virtual patients.  
Two studies [25; 37] concern two laparoscopic commercial simulators: the LapSim@virtual simulator (Surgical Science Inc, Minneapolis, MN, USA) and the ProMIS hybrid simulator (Haptica, Dublin, Ireland) that offer different training scenarios with different levels of complexity. No outcome has been reported on this aspect of simulation. The former simulator (the LapSim) is a high-fidelity simulator available in two versions: with and without haptic feedback. This modular system consists of laparoscopic instruments as interfaces connected to a computer. Modules include basic laparoscopic skills, ranging from navigation to more advanced skills (e.g., coordination, grasping, cutting, clip applying, suturing, etc.) and multiple surgical procedures (e.g., cholecystectomy, appendectomy, laparoscopic gynecology, etc.). The latter system (the ProMIS) combines a laparoscopic mannequin connected to a laptop with integration also into a virtual environment. It uses real surgical instruments which are tracked during the tasks to provide an accurate and objective assessment of the user's performance. The system includes both basic laparoscopic tasks and entire surgical procedures, such as appendectomy, colectomy, cholecystotomy, etc. Different physical models (such as suturing pads) can be inserted into the mannequin; for example, in [25] the authors used the MISTELS (McGill Inanimate System for Training and Evaluation of Laparoscopic Skills) task set, whereas in [37] the authors used an object-positioning module and a gallbladder model during the training sessions.  
In [44], the authors developed an AR simulator for laparoscopic cholecystectomy. The key feature of this system is the capability to create physical and virtual scenarios with different degrees of complexity, allowing the trainee to acquire both the dexterity necessary for good practice and the decision-making skills. Due to the morphological and topological variations that occur naturally in human hepatobiliary anatomy, the authors predisposed physical models of different anatomical variations of the arterial and biliary trees and implemented an easy connection/disconnection coupling to facilitate any substitution on demand. This gives the tutor the possibility to choose the anatomical variations according to the trainee's level of experience.