Virtual-reality distraction and cold-pressor pain tolerance: does avatar point of view matter?

Virtual reality facilitated exercise improves pain perception: A crossover study

STUDY OBJECTIVE

Both virtual reality (VR) and exercise are recognized for their analgesic and anxiolytic properties. The purpose of this study is to evaluate the ability of VR-facilitated exercise to modulate pain.

DESIGN

Within-subject cross-over clinical trial.

SETTING

The Stanford Chariot Program conducted this study at Lucile Packard Children's Hospital Stanford (LCPHS).

PATIENTS

Healthy participants meeting inclusion criteria were recruited by volunteer solicitation from LCPHS.

INTERVENTIONS

Participants were randomized by hand dominance and subjected to a standardized cold pressor test with no VR or exercise. After a 5-min wash-out period, participants repeated the test on their other hand while experiencing a VR-facilitated exercise condition. Pain sensitivity, pain tolerance, and sympathetic activation data were collected during both conditions.

MEASUREMENTS

Pain sensitivity was scored 0-10 and collected every 30 s. Pain tolerance was recorded as the duration a participant could endure the painful stimuli. Sympathetic activation was measured by skin conductance response density (SCRD) and recorded in 30 s epochs by a biosensor. In all analyses, data were nested by participant.

MAIN RESULTS

Forty-one participants completed both interventions. Pain sensitivity was reduced in the VR-facilitated exercise condition (p < 0.0001). There was no difference in pain tolerance between conditions. While both conditions resulted in an increase in sympathetic activity, SCRD was higher at all time points in the VR-facilitated exercise condition.

CONCLUSIONS

The reduction in pain sensitivity indicates VR-facilitated exercise results in improved pain perception. VR-facilitated exercise may be especially useful for patients with chronic pain or other conditions requiring physical therapy, where pain may be exacerbated by exercise.

Quantifying virtual reality pain modulation in healthy volunteers: A randomized, crossover study

STUDY OBJECTIVE

Virtual reality (VR) is an emerging tool to reduce pain and anxiety during procedures. Although VR's clinical benefits are reported, biometric data quantifying VR's effect on pain tolerance is lacking. We used time-lapse, subjective, and biometric data to evaluate VR's effect on modulating pain.

DESIGN

Randomized, controlled crossover within-subject clinical trial.

SETTING

This study was conducted in the Chariot Lab at Lucile Packard Children's Hospital and outdoors at Stanford University School of Medicine.

PATIENTS

156 healthy volunteers were included.

INTERVENTIONS

Participants underwent pain-inducing ice immersions while connected to biometric sensors. Participants were randomized to immerse their dominant or non-dominant hand with VR or control (no VR) for one immersion, and then crossed-over to the other hand for the second immersion. We instructed participants to submerge their hand until they reached their pain tolerance or until four minutes elapsed.

MEASUREMENTS

Outcomes included ice immersion duration, perceived pain scores, and skin conductance response density (SCRD), a marker of sympathetic arousal. We used survival analysis and mixed effects models to compare measurements with and without VR.

MAIN RESULTS

153 participants were included in the analysis. Participants with VR were 64% less likely to remove their hands from the ice bath throughout the immersion's duration compared to control (P < 0.001). Participants with VR reported significantly lower pain scores after controlling for dominant hand treatment assignment, VR vs. no VR treatment order, and gender (P < 0.001). SCRD increased as time progressed for both VR and control groups (P = 0.047 combined), with no significant mean group differences.

CONCLUSIONS

Participants with VR were more likely to survive the 4-min ice bath challenge longer and with lower levels of pain perception, supporting VR's effectiveness as a distraction tool during painful procedures. We observed no differences in sympathetic response when comparing VR to no VR.

The Soothing Sea: A Virtual Coastal Walk Can Reduce Experienced and Recollected Pain

Virtual reality (VR) distraction has become increasingly available in health care contexts and is used in acute pain management. However, there has been no systematic exploration of the importance of the content of VR environments. Two studies tested how interacting with nature VR influenced experienced and recollected pain after 1 week. Study 1 (n = 85) used a laboratory pain task (cold pressor), whereas Study 2 (n = 70) was a randomized controlled trial with patients undergoing dental treatment. In Study 1, nature (coastal) VR reduced both experienced and recollected pain compared with no VR. In Study 2, nature (coastal) VR reduced experienced and recalled pain in dental patients, compared with urban VR and standard care. Together, these data show that nature can improve experience of health care procedures through the use of VR, and that the content of the VR matters: Coastal nature is better than urban.

Sound can enhance the analgesic effect of virtual reality

Virtual reality (VR) technology may serve as an effective non-pharmacological analgesic to aid pain management. During VR distraction, the individual is immersed in a game presented through a head-mounted display (HMD). The technological level of the HMD can vary, as can the use of different input devices and the inclusion of sound. While more technologically advanced designs may lead to more effective pain management the specific roles of individual components within such systems are not yet fully understood. Here, the role of supplementary auditory information was explored owing to its particular ecological relevance. Healthy adult participants took part in a series of cold-pressor trials submerging their hand in cold water for as long as possible. Individual pain tolerances were measured according to the time (in seconds) before the participant withdrew their hand. The concurrent use of a VR game and the inclusion of sound was varied systematically within participants. In keeping with previous literature, the use of a VR game increased pain tolerance across conditions. Highest pain tolerance was recorded when participants were simultaneously exposed to both the VR game and supplementary sound. The simultaneous inclusion of sound may therefore play an important role when designing VR to manage pain.

Feeling the burn: When it looks like it hurts, and belongs to me, it really does hurt more

We examined changes in pain sensitivity in the rubber hand illusion (RHI). Experiment 1 investigated changes in pain tolerance immediately after a "healthy" and "wounded" RHI when immersing the hand in a cold pressor ice bath. There was 19% increased pain tolerance and increased perception detection threshold after the healthy RHI, but 11% reduction after the wounded RHI. Experiment 2 examined pain experience during the wounded RHI with capsaicin-induced hyperalgesia. Pain intensity and unpleasantness was higher on the illusion arm during the synchronous RHI, compared with asynchronous trials. There was no change in pain experience on the control arm, and both arms had similar pain sensitivity after the experiment. Our results highlight the impact of embodying a substitute limb on pain, with increased tolerance and reduced tactile sensitivity when the fake limb is healthy and apparently pain-free, but increased pain sensitivity when the self-attributed limb appears to be wounded.

Meta-analysis of digital game and study characteristics eliciting physiological stress responses

Digital games have been used as stressors in a range of disciplines for decades. Nonetheless, the underlying characteristics of these stressors and the study in which the stressor was applied are generally not recognized for their moderating effect on the measured physiological stress responses. We have therefore conducted a meta-analysis that analyzes the effects of characteristics of digital game stressors and study design on heart rate, systolic and diastolic blood pressure, in studies carried out from 1976 to 2012. In order to assess the differing quality between study designs, a new scale is developed and presented, coined reliability of effect size. The results show specific and consistent moderating functions of both game and study characteristics, on average accounting for around 43%, and in certain cases up to 57% of the variance found in physiological stress responses. Possible cognitive and physiological processes underlying these moderating functions are discussed, and a new model integrating these processes with the moderating functions is presented. These findings indicate that a digital game stressor does not act as a stressor by virtue of being a game, but rather derives its stressor function from its characteristics and the methodology in which it is used. This finding, together with the size of the associated moderations, indicates the need for a standardization of digital game stressors.

GASICA: generic automated stress induction and control application design of an application for controlling the stress state

In a multitude of research and therapy paradigms it is relevant to know, and desirably to control, the stress state of a patient or participant. Examples include research paradigms in which the stress state is the dependent or independent variable, or therapy paradigms where this state indicates the boundaries of the therapy. To our knowledge, no application currently exists that focuses specifically on the automated control of the stress state while at the same time being generic enough to be used in various therapy and research purposes. Therefore, we introduce GASICA, an application aimed at the automated control of the stress state in a multitude of therapy and research paradigms. The application consists of three components: a digital stressor game, a set of measurement devices, and a feedback model. These three components form a closed loop (called a biocybernetic loop by Pope et al. (1995) and Fairclough (2009) that continuously presents an acute psychological stressor, measures several physiological responses to this stressor, and adjusts the stressor intensity based on these measurements by means of the feedback model, hereby aiming to control the stress state. In this manner GASICA presents multidimensional and ecological valid stressors, whilst continuously in control of the form and intensity of the presented stressors, aiming at the automated control of the stress state. Furthermore, the application is designed as a modular open-source application to easily implement different therapy and research tasks using a high-level programming interface and configuration file, and allows for the addition of (existing) measurement equipment, making it usable for various paradigms.

Distraction of attention with the use of virtual reality. Influence of the level of game complexity on the level of experienced pain

: Research done in recent years shows that Virtual Reality (VR) can be an effective tool for distracting attention from pain. The purpose of this study was to test how the complexity of Virtual Environment (VE) influences the experienced intensity of thermal pain stimuli.

A within-subjects design experiment was conducted, using cold pressor test for pain stimulation. Research was done on 31 students of Wroclaw Universities. Participants played games created for the purpose of the study, using head mounted displays and movement sensors. Two Virtual Environments differing in the level of complexity and non-VR control condition were used. The order of all conditions was counterbalanced.

Participants reported significantly lower pain intensity (Visual Analogue Scale) after playing the high complexity game, compared to the low complexity game. There were also significant differences between non-VR control condition and high complexity game, but not between non-VR and low complexity game. The pain tolerance (measured by time of keeping the hand in cold water) was significantly higher in both VR conditions comparing to non-VR conditions. However, no significant differences between VE’s were found in pain tolerance ratings. Results of this study provide preliminary evidence that game complexity can be related to pain experience during VR interventions.