Hoffman, H.G., Patterson, D.R., Carrougher, G.J. (in press). Use of virtual reality for adjunctive treatment of adult burn pain during physical therapy: A controlled study.  The Clinical Journal of Pain. 

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*Hunter G. Hoffman, Ph.D., +David R. Patterson, Ph.D.
+Gretchen J. Carrougher, R.N., M.N.

+Department of Rehabilitation Medicine, 
University of Washington School of Medicine, P.O. Box 359740, Seattle, WA., 98104, *U.W. Human Interface Technology Laboratory, P.O. Box 352142, Seattle, WA., 98195

Address correspondence to 
David R. Patterson, Ph.D., A.B.P.P., A.B.P.H., 
Department of Rehabilitation Medicine, 
University of Washington School of Medicine, 
325 9th Avenue, 
P.O. Box 359740, 
Seattle, WA., 98104-2499
phone number: (206) 731-3418
fax number (206) 731-8580

Abstract:
	Objective: The pain experienced by burn patients during physical therapy range of motion exercises can be extreme, and can discourage patients from complying with their physical therapy. We explored the novel use of immersive virtual reality (VR) to distract patients from pain during physical therapy.  
	Setting:  Burn care unit at a regional trauma center.
	Patients: Twelve patients aged 19-47 years (average of 21% total body surface area burned) performed range of motion exercises of their injured extremity under an occupational therapist’s direction. 
	Intervention:  Each patient spent 3 minutes of physical therapy with no distraction and 3 minutes of physical therapy in VR (condition order randomized and counterbalanced). 
	Outcome measures: Five visual analog pain scores for each treatment condition served as the dependent variables.  
	Results: All patients reported less pain when distracted by VR, and the magnitude of pain reduction from VR was statistically significant, e.g., time spent thinking about pain during PT dropped from 60 mm to 14 mm on a 100 mm scale. The results of this study may be examined in more detail at www.hitl.washington.edu/projects/burn/.
	Conclusions: Results provided preliminary evidence that virtual reality can function as a strong nonpharmacologic pain reduction technique for adult burn patients during physical therapy, and potentially for other painful procedures or pain populations.
	Keywords: Burn pain-Virtual reality-Distraction-Analgesia.

Use of virtual reality for adjunctive treatment of adult burn pain during 
physical therapy: A controlled study.
Discussion. 
	Immersive virtual reality reduced the amount of pain reported and the amount of time burn patients even spent thinking about their pain during the VR segment of physical therapy.  The experimental effect size was large and was statistically significant, and nearly every patient approached readily agreed to participate in the study (a sign up rate of over 90%).  These results provide the first available evidence from a controlled study that virtual reality may serve as a useful, much needed, and popular pain reduction technique for patients with burn injuries.  Because burn wound care often makes people anxious, and such anxiety has been shown to exacerbate pain33, we predicted that VR would reduce anxiety during physical therapy.  There was a difference in the mean scores in the predicted direction but this was not statistically significant, perhaps because initial anxiety ratings were low (i.e., a floor effect).
	There are some limitations to the current study.  Although care was taken to standardize treatment protocol, the occupational therapists were aware of the treatment condition, and could have inadvertently treated patients more gently in VR.  Encouragingly, maximum range of limb motion stayed the same or improved in the VR condition in 10 out of the 12 patients.  Anecdotally, the therapists reported that events occurring in the virtual world caused some patients to tense up initially, but that patients displayed equal or better range after they adjusted to being in VR.  Similarly, patients were also not blind to experimental conditions, and may have been motivated to under-report pain levels during the VR task (to report less pain than they actually experienced).  A double blind replication of the present study is possible and needed, though somewhat difficult to achieve.  Both the occupational therapist and patient should be kept unaware of what experimental condition the patient is in, and if possible, range of motion measures should be re-measured by a second rater who is kept blind to condition, who also remains unaware of the first rater’s measure, to allow the assessment of inter-rater reliability. 
	Hoffman, Garcia-Palacios, Everett and Sharar34 recently conducted an ischemic pain experiment designed to reduce demand characteristics.  Hoffman et al.23 speculate that the more present participants felt in the virtual environment, the more of their attention drawn into VR.  If so, higher presence should lead to more effective VR pain reduction.  To test this hypothesis, Hoffman, et al.34 conducted a subject-blind manipulation of pain control effectiveness. Without the subjects’ knowledge, subjects were randomly assigned to one of two treatment groups, either a “low technology VR condition” or a “high technology VR condition”.  Both groups received VR, as well as a control condition involving ischemic pain with no distraction, so both experimental groups were under similar contextual demand characteristics.  As mentioned, participants remained unaware that there was another group with a different (more or less attention grabbing) virtual world (i.e., they were kept blind to the experimental manipulations).  As predicted, manipulating factors known to affect the illusion of presence in VR influenced presence and pain reduction effectiveness.  The high tech VR group felt considerably more present in the virtual environment (i.e., they felt more like they were “in a place” when in the virtual world), and reported more effective pain reduction than the group getting low tech VR.  The results of Hoffman et al.34 reduce the plausibility of a demand characteristics explanation for VR pain reduction, and implicate an attentional mechanism for the effect.
	Controlled studies exploring the potential applications of VR to adjunctive pain control in pediatric and adolescent populations are needed since children are often severely undertreated for acute pain and anxiety35.  In addition to physical therapy, patients with severe burns typically experience daily dressing changes and cleansing of the wounds to prevent infection.  Most patients with severe burns report severe to excruciating pain during these dressing changes, despite use of opioid analgesics36.  Hoffman, et al.27 recently reported large reductions in pain for two pre-adult patients undergoing burn wound dressing changes, wound cleansing and staple removal from skin grafts.  Both patients were pre-medicated with the usual opioids, and were then distracted by an immersive virtual reality environment and then by Nintendo64 (or vice versa) during a single wound care session.  VR distraction was dramatically more effective for pain reduction than the Nintendo64 video game.  Since case studies must, by nature, be interpreted with caution37, a follow-up study using Hoffman et al.’s 27 design (with a larger number of subjects) is needed.
	Results from analog laboratory experiments converge with the results of the present study.  Hoffman, et al.,38 recently found that laboratory induced ischemic pain dropped in half when college students went into virtual reality compared to no VR.  A separate task not involving pain was performed to test the assumption that VR is attention-grabbing.  As predicted, young adult students in VR showed a significant reduction in performance on an auditory task (monitoring a string of numbers from a tape recorder for 3 odd numbers in a row) compared to no VR (monitoring numbers from the tape recorder while wearing a VR helmet that was turned off).  VR distracted attention away from the student’s primary task of monitoring the numbers.  Students made significantly more errors in VR.  Consistent with our interpretation of the present findings, Hoffman, et al.’s38  results implicate the contribution of an attentional mechanism for VR pain control.
	Additional research exploring the mechanism by which VR pain reduction is achieved is warranted.  Placebo effects can strongly influence pain perception in some patients, and could contribute to VR pain reduction.  Beecher (1959, cited by Melzack5 ) found that about 35% of the patients tested experienced pain relief from severe pain such as post-surgical pain when administered a placebo (i.e., sugar pills).  Unfortunately, more recent studies indicate that patients experience less and less pain reduction each time placebos are administered (described by Melzack5).  In the present study, one hundred percent of the patients showed pain relief with VR, but patients spent only 3 minutes of physical therapy in VR (and 3 minutes in no VR).  Since patients may undergo dozens of physical therapy sessions, each lasting much longer than 3 minutes, future research is needed to assess whether VR remains effective for pain management with repeated use and longer duration and should explore ways to maximize analgesia effectiveness.
	Although simulator sickness39 was not a problem in this short study, it should be monitored closely in any medical use of VR.  Consistent with previous findings 30, 31 patients in the present study indicated that they felt a moderately strong illusion of being in a place (the sensation of “presence”) while in the KitchenWorld, and found the virtual objects somewhat realistic. The use of tactile feedback as realistic as the furry spider in SpiderWorld is rare in VR research, as is the use of a unique “edible” virtual object.  Converging evidence from multiple senses (e.g., a virtual candy bar that patients could see, smell, touch and taste) likely contributed to the effectiveness of our VR treatment.  However, there is much room for improving “presence and realism” in future VR applications specifically designed for treating pain.  New virtual worlds, custom built to be attention grabbing, (e.g., an immersive fighter jet missiond) could produce even larger reductions in pain.  Such new worlds can take advantage of the versatility of VR software.  For example, in addition to distracting patients, virtual worlds could prove useful for motivating patients to make desired limb motions, using behavioral reinforcement and other techniques.
	The cost of an immersive VR system has dropped dramatically since the mid 90s, and additional price reductions are inevitable.  At the same time, the quality and portability of VR has increased dramatically, benefiting from the enormous improvements in more conventional computer technology (e.g., cheaper memory, cheap and fast graphics accelerators, higher information processing capabilities of the hardware, and also a dramatic maturation in the quality of VR world building software commercially available5 ). VR for physical therapy is becoming much more affordable.  In contrast, the excruciating pain experienced during bandage change and staple removals in the scrubtank should be treated with the most attention-grabbing systems possible.  A VR system that is completely water-friendly is possible e, but is presently very expensive.
	To summarize, the present study provides encouraging initial support for the use of VR as a technique for controlling pain during physical therapy.  At the same time, our effects were limited to brief and single sessions of physical therapy.  Additional empirical studies will be needed to determine whether virtual reality can become a viable form of nonpharmacologic pain control in everyday medical practice.  Since burn wounds are widely considered to be among the most painful injuries a person can endure, techniques that prove effective for treating burn pain will likely prove effective for other painful procedures  (e.g., dental pain, pain from brief painful cancer procedures, situations where the patient needs to be conscious, or where the procedure is too frequent to use general anesthesia).  Since excessive pain is such a vexing problem for the medical community, and these preliminary results support the notion that VR might prove valuable for pain control, additional research on this topic is warranted.

Acknowledgements.  NIH grant GM42725-07, The Paul Allen Foundation for Medical Research, the International Association of Fire Fighters, the U.W. Royalty Research Fund, the Bishop Foundation. Thanks also to Thomas Furness III, and Ross Chambers and his
generous contributers. 

Table 1. 
	Mean VAS (mm) Control	Mean VAS (mm) VR	t(11) value	p value	SE (difference)	
Time1	60.75	13.67	5.19	.000	9.07	
Worst pain	42.00	19.92	4.02	.002	5.49	
Average pain	36.33	14.67	4.08	.002	5.31	
Bothersomeness	46.08	13.84	4.26	.001	7.58	
Unpleasantness	43.18	10.09	5.13	.000	6.45	
1Time spent thinking about pain during the procedure.

					Figure 1

Figure 1.  Burn patient sees an animated 3-D tarantula in SpiderWorld (right) and can touch it’s real world twin (a toy spider) in the real world (held on a string above in left photo with position tracker attached to toy spider’s abdomen).

Figure 3:  Results show a trend of more pain and anxiety reduction for people reporting  higher presence in VR.