The nomenclature surrounding immersive reality (IR) has evolved, and in this review, we provide some definitions to assist the reader. We use IR as an overarching term encompassing virtual reality (VR), augmented reality (AR), and mixed reality (MR), although other umbrella terms, such as extended reality, can also be found in the literature [1,2]. VR is any type of computer-generated immersive environment that users can interact with, including both 2D and 3D experiences. AR involves overlaying computer-generated elements on a real-world environment, and MR blends aspects of VR and AR [3,4], capturing both real-world and virtual elements in 3D and allowing for interaction across these realms [5].

IR experiences are often facilitated using a head-mounted display (HMD or headset), a piece of hardware worn on the face of the user, surrounding their field of view, with 1 or 2 small displays showing stereoscopic computer-generated imagery [6]. In this form of VR, users wearing an HMD can only perceive images of the virtually generated world displayed on the screens. This allows a user to experience a fully immersive, computer-generated 3D environment and interact with objects using handheld controllers or a set of virtual hands that mimic their own. More recently, with advances in consumer-level hardware, many IR headsets allow users to physically walk around within a defined interactive VR environment. In contrast to VR headsets, AR and MR headsets allow the user to see the real world while immersed in an overlaid computer-generated environment within the field of view of the headset.

Consumer-level HMDs most commonly used for clinical and medical education purposes incorporate variable levels of functionality (Table 1). For example, different devices are capable of tracking various types of motion. Simple systems with 3 degrees of freedom can only detect rotation around a fixed point. Newer, more complex systems, with 6 degrees of freedom can detect rotation and position in 3D space.

Regarding HMDs, 3 degrees of freedom devices can only detect where you are looking (the rotation and tilt of your head) but not your position in space (ie, whether you move forward or backward, left or right, or crouch down). Devices with 6 degrees of freedom can detect all the abovementioned types of motion using either sensors built into the device itself or external sensors, such as tripod or wall-mounted hardware.

Similar to headsets, VR controllers with 3 degrees of freedom have limited tracking ability, while newer controllers with 6 degrees of freedom allow a more naturalistic, full range of motion (eg, extending your controller in real life will be replicated in VR). Eye tracking refers to an extra set of lenses within the HMD, which tracks the movement of each eye. This allows the device to track where the user is looking and, in some cases, it allows interaction with the virtual environment through changes in gaze alone [31-33]. Hand tracking uses a front-facing camera on the HMD to track a user’s hands and project them into the virtual environment, allowing users to interact with the virtual environment without the need for controllers.

Handheld devices (eg, cell phones and tablets) can also be used for AR, by observing digital images overlaid on the real world using the camera viewer. However, these devices offer limited functionality as they have only a small field of view and are not ergonomic, as they must be held up by the user.

Immersion is the ability of a system to create the sensation of “presence,” the subjective feeling of existing in a computer-generated world [34]. This is created in computer-based simulations by providing sensory input, including visual, auditory, and tactile (ie, haptic feedback) stimuli. Placing an individual in an IR system with these stimuli creates the sensation of being physically present in a virtual environment. Advancements in computational processing power and associated decreases in the size of electronic components have led to lower costs and rising availability of consumer-level IR technologies. This increase in availability has been accompanied by a parallel increase in the adoption of virtual-based simulation in medicine and beyond [35].

Historically, 2D worlds, which lack the increased sense of presence provided by newer 3D immersion technology, have also been labeled immersive experiences. In the context of medicine, this has mainly been limited to medical education, where learners view a 2D screen with a virtual image of a simulated task to be practiced. Many examples of simple 2D simulation exist in surgical training [36,37] and anesthesia [38-42], where students view virtual anatomical images on a screen and use partial task trainers or practical tools (eg, endoscopes, bronchoscopes, and surgical instruments), which provide haptic feedback to practice their technical skills.

Affordable HMDs and 360° cameras developed in recent years have allowed educators to increase immersion in IR educational experiences. Instead of watching on a 2D screen, learners can now be immersed in 360° experiences using headsets to experience real or animated clinical environments. As reduced work hours for medical trainees has resulted in fewer clinical learning opportunities, IR has emerged as an alternative method to supplement traditional clinical curricula. In addition, during the global COVID-19 pandemic, where social distancing and remote learning presented challenges for clinical learning, IR enabled students and residents to continue participating in interactive training. However, the literature is just beginning to examine how IR modalities can most effectively be incorporated into clinical teaching curricula.

Another relevant component of teaching curricula is simulation-based training. Simulation is an educational technique that allows interactive, immersive activity by recreating all or part of a clinical experience without exposing patients to associated risks [43]. Historically, full-body manikin simulation has been proposed as an adjunct to clinical learning, complementing clinical experience. Simulation in medical education is a well-established pedagogical practice [44], providing a viable alternative to practice with actual patients, whereby medical trainees are afforded the opportunity to train until they reach a specific competency level. Simulation ranges from decontextualized bench models and VR-based environments to high-fidelity recreations of actual operating rooms [45]. Simulation can engage the trainee in the progressive accumulation of knowledge through deliberate practice, allowing for careful matching of the complexity of the learning environment to the trainees’ current level of advancement [46]. Although simulation is widely used in medical education, it is often resource intensive, cost prohibitive [47] and requires learners to physically attend simulation centers. A survey of 154 anesthesiologists found that insufficient time and training opportunities were major barriers to taking part in simulation-based education, with 48% of respondents saying that they would be more likely to attend simulation-based courses if they were hosted at their own hospital [48].

Current advances in IR technology are addressing these limitations through the development of innovative, immersive experiences using cost-effective, consumer-level hardware capable of engaging trainees. A major advantage of IR over manikin-based simulation is increased accessibility, as learners can use the equipment on-site or access IR educational applications remotely. IR equipment can be set up in small spaces (eg, call rooms and conference rooms) with minimal time requirements so that the curricula can be delivered instantaneously in perioperative settings. In addition, although there are costs associated with developing IR applications, the end products can be made modular with the potential for both learning and assessment embedded within. IR curriculum delivery is highly cost-effective and can be easily scaled for additional learners with minimal expense, unlike manikin-based programs. These advantages may result in increased feasibility and reduced costs for IR-based simulation training, although this must still be verified using appropriate cost-benefit studies.

In addition to the use of IR simulation for education and training purposes, IR technologies are increasingly being used directly in patient care, both in patient-centric interventions (eg, as a distraction during painful procedures) and by health care providers (eg, real-time AR-image guidance). In this review, we discuss the theory underlying the use of IR technology in both medical education and clinical care as well as the evidence supporting specific examples relevant to practicing anesthesiologists.

This narrative review aimed to identify uses of IR relevant to practicing anesthesiologists. As such, we focused on perioperative applications and applications related to techniques in which anesthesiologists commonly take part (eg, fiber-optic intubation). Applications of IR focused on addressing pain or anxiety in instances where an anesthesiologist is not normally present (eg, burn wound dressing changes [49]) were excluded. Similarly, while a large amount of research has been done in the area of pediatric anesthesia, we chose to focus on IR applications relevant to those practicing in adult populations. IR applications in pediatric populations have been described elsewhere [50-52]. Finally, we focused on describing existing applications of IR in anesthesia, including up-to-date clinical protocols, while a review focused on theoretical and future applications has been recently published elsewhere [53].

Relevant publications were identified using PubMed and search terms including “Virtual Reality” AND (“anesthesia” OR “Anaesthesia” OR “Anesthesiology” OR “Anaesthesiology”); “Augmented Reality” AND (“anesthesia” OR “Anaesthesia” OR “Anesthesiology” OR “Anaesthesiology”); vital AND signs AND monitoring AND anesthesia AND display; (“anesth*” OR “anaesthe*”) AND (virtual reality OR immersive reality OR augmented reality OR mixed reality OR 360 video) AND (simulation) AND (education) AND (technology) AND (pedagogy OR teaching); (“anesth*” OR “anaesthe*”) AND (virtual reality OR immersive reality OR augmented reality OR mixed reality OR 360 video) AND (simulation) AND (education) AND (pedagogy OR Teaching) AND (clinical medicine); (“anesth*” OR “anaesthe*”) AND (virtual reality OR immersive reality OR augmented reality OR mixed reality OR 360 video). The literature search included articles published from inception to the date of the search, July 5, 2023. Additional references were identified from the reference lists of the selected papers.

The continued development of low-cost, consumer-level IR technology is facilitating a shift in pedagogy from traditional 2D images and videos to learning through interactive IR environments. This is particularly important in medical education, where knowledge acquisition usually includes greater experiential, self-directed, and hands-on learning than in many other disciplines [4]. As described in this paper, IR technologies have already been used to educate trainees, prepare health care providers, and help patients. Over time, emerging technologies, such as multitouch displays, telepresence (an immersive meeting experience that offers high video and audio quality), 3D environments, natural language processing, and artificial intelligence (AI) software [194], have the potential to transform not only medical education and practice but also teaching and learning in general [195].

The advances in technology discussed above in the Introduction section allow for higher fidelity, increased presence, and creation of new applications in the field of IR, but it is also important to consider how existing IR technologies can extend the impact and reach of experts in the field of anesthesia. For instance, IR can be used in conjunction with traditional or virtual simulations to facilitate feedback and decrease demands on facilitator time. For example, IR can assist with the initial prebriefing [196,197], wherein participants are oriented to objectives and frameworks for their upcoming experience by facilitating a “flipped classroom” experience [198]. In this case, learners are virtually oriented to the simulation center from home, reducing the time required of facilitators and the overall time spent at the simulation center, allowing more time for participation in the simulated scenarios upon their arrival.

Similarly, telesimulation and telementoring, whereby a skilled practitioner can remotely guide a less experienced colleague through a complex procedure, either for educational purposes [199-201] or in an emergency situation [202], have been successfully used in surgical contexts [199-202]. The most complex versions of these apparatuses allow for annotations and even the movements of surgical tools, manipulated by an instructor, to be projected onto the surgical field of view of a colleague using AR technology [200,203]. This provides a proof of concept for using this technology to extend anesthesia services and aid in training anesthesiologists in underserved and rural communities, where they often work in challenging, underresourced environments to serve populations with high needs. In Ontario, Canada, the government is paying attention to the needs of such populations, especially Indigenous populations [204], as they have higher mortality rates and poorer health outcomes compared to urban populations [205]. IR applications, including telementoring and IR simulation training delivered via remote technology, are tools that can be used to advance health care in these regions and bring it in line with urban centers.

One noteworthy strength of IR over other simulation strategies is the ability to readily reimmerse in a simulation. For example, during feedback stages, IR allows both the facilitator and learner to be reimmersed in the simulation scenario. This can trigger the same emotional cues as when the learner was managing the simulated crisis, heightening recall and potentially leading to more fruitful discussions. This would similarly apply to self-debriefing, where learners are able to visualize the scenario from their own perspective but without the cognitive and emotional burden of managing the case, facilitating focus on the decision-making cues. Finally, during interprofessional training, immersive 360° cameras can be oriented to provide the point of view of each participant (eg, a surgeon could use an HMD to be immersed in the anesthesiologist’s point of view), potentially leading to a greater appreciation of one another’s roles.

The importance of well-being in health care providers has gained greater attention in recent years and presents another area where IR may have utility. Emerging evidence suggests that IR interventions, such as guided relaxation, could also help reduce stress and burnout among health care practitioners both during training [206] and in high-stress situations, such as a pandemic [207,208]. Intriguingly, a recently published small study of 20 nurses has also provided preliminary evidence that the increased usability of VR patient education compared to traditional approaches may lead to improved health care provider satisfaction and reduced burnout scores [209]. While further studies are needed, this early evidence suggests potential indirect benefits of IR, which have not been fully characterized.

As technology advances, the ways we interact with it also evolve. Instead of interacting through touchscreens or hand controllers, we will be able to interact directly through hand motions and eye movement tracking. This may accelerate as promising design breakthroughs, such as transparent interfaces, are integrated into IR systems. AI is another emerging technology that can be incorporated into medical training and presents a potentially paradigm-shifting advancement. For instance, an early study using AI-based feedback has shown evidence for effectiveness in achieving learning goals [118]. In a simulated operating room fire scenario, this study showed a significant performance improvement when an AI-guided virtual trainer provided timely feedback to users in the virtual operating room.

Further technological advances will occur in the field of haptics. Basic haptic (touch simulation) feedback is already widely available at the consumer level through devices that provide vibration feedback (eg, video game controller “rumble packs” or mobile phone vibrations). Furthermore, pseudohaptics [210,211], where illusory haptic sensations are created using combinations of audio, visual, and kinesthetic cues, has also been used to convey various touch-based properties [212-214]. However, currently available consumer-level haptic devices cannot provide the high level of fidelity and range of motion required to simulate many tasks realistically [215], and high-fidelity haptic solutions are cumbersome, complex, and often cost prohibitive [216,217]. As consumer interest in haptics grows, haptic devices capable of providing force feedback beyond simple vibrations will become more widespread. Notably, integrating haptic feedback into IR enhances immersion by simulating sensations and has been used in medical simulations, including training and simulation of medical procedures, allowing trainees to practice realistic interactions in a safe environment.

Adopting new technological advances in IR systems benefits from the increasing availability of so-called maker spaces. These are collaborative workspaces that contain equipment such as laser cutters, computer numerical control machines, soldering irons, and 3D printers that can easily create innovative, customizable, and cost-effective learning tools. 3D printing, in particular, which is becoming widespread in part due to decreased cost, allows digitally designed objects to be replicated in the real world, facilitating the merger between IR and real physical form, albeit with some limitations [4]. In the context of anesthesia, this creates the potential for faithful recreations of anatomical features (eg, airway or spinal column) to be generated using imaging data for use in training or preprocedure planning [218,219].

While the potential benefits of IR simulation are considerable, the potential downsides of IR technology must also be considered. This includes the presence of cybersickness (negative symptoms associated with immersion in a digital world, including feelings of nausea, dizziness, or headache), which can limit usefulness in both educational and clinical contexts [220,221]. The incidence of cybersickness resulting from the use of IR systems depends on many different factors (eg, frame rate, field of view, sex, and previous game playing experience) and ranges from common to very rare [222]. The heterogeneity of both IR technology and interventions studied likely contributes to this variability [220]. However, both practical factors, such as limiting exposure duration, and technological factors, such as improved latency and higher levels of immersion, are known to reduce cybersickness [177,220,223], with 1 recent review concluding that benefits outweigh risks, at least in some patient populations [221]. Further research is needed to identify factors that can reduce unwanted side effects, such as cybersickness, while preserving the many advantages of IR technology.

Furthermore, it must be acknowledged that potential costs associated with the initial implementation of IR technologies, especially in low-resource settings, could be a barrier and potentially exacerbate existing inequality in health care outcomes. Until recently, IR technology was expensive, cumbersome, and restricted to several large institutions and research centers. However, recent increases in computational processing power and the accompanying decrease in the size of electronic components have led to decreasing costs and rising availability of consumer-level technologies (Table 1). The introduction of freely available game engines and mobile devices (eg, tablets and smartphones) capable of reproducing education-worthy environments with adequate fidelity has made IR technology an exciting and emerging field [4]. Widely available low-cost options, such as Google Cardboard [224] and other smartphone-based IR headsets, are suitable for many of the most common clinical uses of IR, such as patient education and pain distraction [134,225,226]. This suggests that the implementation of IR technology does not need to be limited to high-resource settings.

However, further research is needed to identify potential barriers and secondary costs related to the implementation of IR programs in different settings. Similarly, if supported by evidence from continued research, wide adoption of IR technology facilitated by funding support in low-resource settings could have an important impact on reducing inequality and generating long-term cost savings.

Despite the great technological advancements made, particularly with respect to computational processing, it is important to consider the limitations of computer hardware with IR applications, particularly when using VR devices. More specifically, designers and developers of IR applications should consider the fidelity of their virtual environments, that is, the level to which a virtual environment resembles the real world it is meant to represent. It is not currently feasible to create a high-fidelity virtual simulation that includes all the senses (ie, input related to sight, sound, and touch). Furthermore, higher-fidelity environments require greater computer processing requirements, which may not be readily available to the average computer users.

Moreover, we must consider the high variability of users who may be susceptible to motion sickness and address accessibility issues, including those related to visual impairment and other disabilities. Finally, as IR technologies in health care are relatively new, it is essential to address ethical concerns. These include the potential short- and long-term effects of virtual environment exposure and HMD use on both patients and health care providers, as well as whether VR headsets should be classified as medical devices?

In this review, we have presented the theoretical basis and evidence supporting the use of IR in the training and clinical practice of modern anesthesiologists. For those interested in implementing IR technology into their own practice, many ready-made technologies exist (Table 1). The processes and techniques required to create and implement low-cost 360° videos and virtual environments using commercially available cameras and software have been described elsewhere [116,193].

Despite recent advancements and increasing interest in IR as a research field, many applications remain in the early stages of development. Robust trials are urgently needed to confirm its clinical and educational effectiveness and to assess its mechanism, educational validity, and cost-effectiveness. While the use of IR technologies may have practical applications in medical education and for a variety of clinical patient populations, it is important to ensure that enthusiasm for this new technology does not overtake available evidence and that all applications are guided by pedagogical theory and evidence-based practice. Thus, there is a unique opportunity to innovate in a promising area of research to show the validity of IR within the anesthesia specialty and demonstrate its ability to optimize learning and clinical delivery of care. Our group founded the University of Toronto’s Collaborative Human Immersive Interaction Laboratory to develop IR solutions for clinical research, medical training, and patient education. The Collaborative Human Immersive Interaction Laboratory also aims to scientifically validate IR as a tool to enhance patient care now and in the future.