Water-Friendly Virtual Reality Pain Control During Wound Care

Transcription

1 Water-Friendly Virtual Reality Pain Control During Wound Care Hunter G. Hoffman, David R. Patterson, Jeff Magula, Gretchen J. Carrougher, Karen Zeltzer, Stephen Dagadakis, and Sam R. Sharar University of Washington Recent research suggests that entering an immersive virtual environment can serve as a powerful nonpharmacologic analgesic for severe burn pain. The present case study describes an attempt to use water-friendly virtual reality (VR) technology with a burn patient undergoing wound care in a hydrotherapy tub. The patient was a 40-year-old male with 19% total body surface area deep flame/flash burns to his legs, neck, back, and buttocks. The virtual reality treatment decreased the patient s sensory and affective pain ratings and decreased the amount of time spent thinking about his pain during wound care. We believe that VR analgesia works by drawing attention away from the wound care, leaving less attention available to process incoming pain signals. The water-friendly VR helmet dramatically increases the number of patients with severe burns that could potentially be treated with VR (see Wiley Periodicals, Inc. J Clin Psychol/In Session 60: , Keywords: burn pain; virtual reality; pain management; analgesia; distraction Severe burns are among of the most painful trauma injuries. Opioids provide the foundation of pain-control strategies for patients with burn injuries. Pain medications usually work well for controlling resting pain. However, patients typically have their bandages changed and their wounds cleaned, disinfected, and monitored on a daily basis. During these wound-care sessions, opioid analgesics are often inadequate for controlling the This research was supported by the Paul Allen Foundation for Medical Research, NIH Grant GM , NIDRR Grant H133A970014, the International Association of Fire Fighters, and local business sponsors (via Ross Chambers). Thanks to Eric Seibel, Ph.D., of the University of Washington HIT lab for important optical engineering advice. Correspondence concerning this article should be addressed to: Hunter G. Hoffman, Box , Human Interface Technology Laboratory, University of Washington, Seattle, WA 98195; hunter@ hitl.washington.edu. JCLP/In Session, Vol. 60(2), (2004) 2004 Wiley Periodicals, Inc. Published online in Wiley InterScience ( DOI: /jclp.10244

2 190 JCLP/In Session, February 2004 patient s pain. Most patients being treated for severe burns report severe to excruciating pain during wound care, despite aggressive use of opioid pain medication (e.g., Carrougher et al., 2003; Choiniere, Melzack, Rondeau, Girard, & Paquin, 1989; Melzack, 1990; Perry, Heidrich, & Ramos, 1981). Pain perception has a strong psychological component. For example, an unusually painful wound-care session may increase the likelihood that the patient will find the subsequent wound-care session painful, through aversive conditioning. According to the influential gate control theory of pain (Melzack & Wall, 1965), higher order thought processes can change how the patient interprets incoming pain signals and can even change the amount of pain signals allowed to enter the brain. Attention, beliefs about pain, expectations, and attributions can modify incoming pain signals from the pain receptors (Turk, Meichenbaum, & Genest, 1983). Psychological techniques can help reduce pain through such mechanisms. These techniques include hypnosis, mental imagery (e.g., picturing oneself without pain on a tropical island), mental effort (e.g., solving math problems during a painful procedure), engaging the patient in conversation, listening to music, or watching a video (Geisser, Bingham, & Robinson, 1995; see Tan, 1982, for a review). For most patients, medications and psychological pain-control techniques combined are still inadequate. Although undermedication is a contributing factor, increasing medication doses is not always possible. Although essential for pain control, the use of opioids is limited by side effects such as nausea, constipation, sedation, itchiness, urinary retention, cognitive impairment, and respiratory depression (Cherny et al., 2001). Immersive Virtual Reality Researchers have recently explored the use of immersive virtual reality (VR) as a powerful psychological pain-control technique. Similar to the psychological pain-control techniques described previously, VR analgesia can be explained in the context of a gatecontrol mechanism. Pain requires conscious attention. Virtual reality lures the spotlight of attention into the virtual world and away from the wound care and associated pain. Patients often have a strong illusion of going into the computer-generated environment, a sensation known as presence. The more patients are drawn into the virtual environment, the less pain they are predicted to experience. We have shown that presence ratings are correlated with the amount of VR analgesia experienced. Our research group previously measured pain levels of two adolescent patients undergoing staple removal from skin grafts while being distracted by VR for three minutes and while distracted by Nintendo for three minutes during a single wound-care session. The patients reported lower pain scores during VR than during the Nintendo video game (Hoffman, Doctor, Patterson, Carrougher, & Furness, 2000). We found a similar pattern of results in a controlled within-subject clinical study involving 12 burn patients. Pain experienced by these patients during physical therapy dropped when they were treated with VR compared to when they received no distraction. Patients performing their physical therapy while in VR also reported large reductions in time they spent thinking about their pain during the VR sessions compared to physical therapy without VR (Hoffman, Patterson, & Carrougher, 2000). More recently, preliminary research indicates that VR can be used over several physical therapy sessions without losing its analgesic effectiveness (Hoffman, Patterson, Carrougher, & Sharar, 2001). Other case studies suggest that VR can help reduce pain felt during dental/periodontal procedures (Hoffman, Garcia, et al., 2001), and pain during physical therapy rehabilitation from muscle/tendon surgery for cerebral palsy (Steele et al., in press).

3 Virtual Reality Pain Control 191 Hydrotanks are sterile bathtubs often used to help loosen and remove bandages, and to clean burn wounds before applying ointments and fresh dressings. Procedural pain is often highest early in the burn recovery process (Choiniere et al., 1989), a time when wound care is most likely to be performed in the hydrotanks. As a result, adjunctive pain control is needed most during wound-care procedures conducted in the hydrotanks. To date, because of safety concerns about electrical shock, patients have not been allowed to wear a conventional VR helmet while sitting in a tub of water. No burn patients have tried VR while in the hydrotanks. The present case study explored whether VR could reduce the extreme pain experienced by burn patients during severe wound care in the hydrotank. If successful, a waterfriendly VR helmet would dramatically increase the number of patients with severe burns who could potentially be treated with VR and would allow patients to receive this analgesia when they need it most. Presenting Problem/Patient Description Case Illustration The patient was a 40-year-old male hospitalized in a regional burn center. He had sustained a 19% total body surface area deep flame/flash burn to his neck, buttock, back, and bilateral legs when an outdoor camping stove ignited his clothing. On the day of the study, the patient was given the following analgesic medications: 60-mg oral Hydromorphone for procedural pain, 20-mg Oxycodone immediate-release on an as-needed basis during the day for treatment of breakthrough pain, and a total of 150-mg Morphone sulfate sustained-release during the previous 24-hr period for control of background pain. Our research group built a photonic, nonelectrical, water-friendly VR helmet that was custom built for use in the hydrotank. Instead of mounting miniature computer screens in the helmet (conventional VR helmet), with the water-friendly helmet, the virtual images are first converted from electrons to photons via two LCD projectors (one per eye, see Figures 1 & 2). After being converted into light images, the real-time VR images are minified with lenses and relayed to the patient via the 15 ft long optic fiber image guides. Each image guide is comprised of 800 1,000 very thin strands of fiber optics packed very closely together into an array. After traveling through the image guides, the light Figure 1. Schematic drawing of the wide field-of-view water-friendly VR system.

4 192 JCLP/In Session, February 2004 Figure 2. Left, the patient using the water-friendly VR system, and (right image) a snapshot of the virtual world the patient goes into during wound care. images enter a custom-made VR helmet where they are magnified and seen by the patient as wide-field-of-view images. Only light, no electricity, reaches the patient s head. Each patient sees two independent computer-generated images of the virtual world (one for each eye), one image slightly offset from the other, which they perceptually fuse into a single three-dimension illusory world with depth, simulating the normal visual depth cue called retinal disparity. The water-friendly VR helmet had approximately horizontal field of view of 105 degrees. Course of Treatment The patient kept his head still and looked around in the virtual world by moving a fingertipcontrolled joystick. The computer quickly updated the virtual environment presented to the user by changing the viewpoint in VR as the user moved the joystick. The patient had the illusion of flying through SnowWorld, a virtual environment we developed with programming help and software tools from and SnowWorld depicts an icy three-dimensional canyon with a river and waterfalls. The patient shot snowballs at snowmen, igloos, robots, and penguins by aiming his gaze and pressing the trigger button on the joystick. The snowballs exploded with animations and three-dimensional sound effects upon impact. While in the hydrotank, the patient spent three minutes of the procedure in VR and three minutes of the procedure with no distraction. By the flip of a coin, he was randomized to receive the VR condition first. Pain ratings and presence ratings, the primary dependent variables, were administered after each of the two treatment conditions during a brief pause in wound care. At each pause, the patient completed several subjective ratings, each on a 10-point graphic scale. The 10-unit horizontal line was labeled with number and word descriptors. The patient rated the amount of time spent thinking about his pain/wound care, his worst pain, pain unpleasantness, and how much fun he had during his wound care. Numerous studies support the reliability and validity of similar rating scales in varying adult-patient populations, including those suffering from a burn (Jensen, 2003). After wound care, the patient also was asked to rate the following items: (a) To what extent (if at all) did you feel nausea as a result of experiencing VR? (none, very much); (b) while experiencing VR, to what extent did you feel like you went into the virtual world? (I did not feel like I went into the virtual world at all, I went completely into the virtual world); and (c) how

5 Virtual Reality Pain Control 193 real did the objects in the virtual world seem to you (completely fake, indistinguishable from a real object). Hendrix and Barfield (1995) described several studies showing the reliability of a similar measure of presence. Outcome and Prognosis On a rating scale of 0 to 10, VR was more effective than a no-distraction control condition. The patient s pain scores decreased from 7 (No VR) to 2 (VR) for sensory pain (worst pain) and decreased from 6 (No VR) to 3 (VR) for affective pain (unpleasantness). The amount of time spent thinking about his pain during wound care dropped from 10 to 3. More specifically, during wound care, the patient reported spending all of the time thinking about his pain in the no distraction condition, and only some of the time thinking about his pain while in immersive VR. On a scale of 0 (no fun at all) to10 (extremely fun), the patient rated VR as a 9 and No VR as a 2. He rated his sense of presence in VR as 6 (moderate sense of going inside), and he rated the realism of virtual objects as a 7. Simulator sickness was 0. The patient was released from Harborview Burn Center a few days after this study, and his burn wounds have now healed. It is unlikely that the single three-minute VR intervention had any effect on the patient s outcome, but longer, repeated treatments with VR analgesia is predicted to improve outcome in future patients. Whether reducing severe pain by adding VR during wound care could improve physical or psychological health of the patient is an important topic for future research. Clinical Issues and Summary This case provides preliminary evidence that entering a virtual environment can help control burn pain during wound care in a hydrotank. The patient s pain ratings showed considerable (e.g., 50%) reduction while in VR relative to a no-distraction control condition. The substantial limitations of case studies are well known (Campbell & Stanley, 1963). Demand characteristics, treatment order effects, novelty, and expectancies were not controlled. The duration of the distraction was only three minutes. Evidence for effectiveness requires converging results from larger, more generalizable, controlled studies. Additional controlled studies on the effectiveness of VR during wound care in the hydrotank with longer treatments on numerous days are needed. Despite these limitations, the magnitude of pain reduction was compelling. Because burn injuries offer a paradigm for management of acute pain in general, if VR proves effective for treating severe pain during wound care in the hydrotank, it will likely be effective for treating pain procedures in a number of other patient populations. Since the degree of pain reported during hospitalization is associated with the degree of postdischarge mental and physical dysfunction (Ptacek, Patterson, Montgomery, & Heimbach, 1995), improved burn-wound-pain management could both reduce suffering and improve outcome. In addition to reducing pain, future immersive virtual worlds will be programmed to encourage/motivate patients to perform specific therapeutic movements, and to make physical therapy and wound care more fun for patients. Reducing excessive pain also may reduce the stress experienced by the patient s family and health care givers. Opioid doses could one day be reduced for patients who respond well to adjunctive VR analgesia, reducing the opioid side effects described earlier. However, considering the magnitude of the problem of excessive pain, our immediate goal and current practice is to add VR without reducing opioid doses.

6 194 JCLP/In Session, February 2004 In addition to showing promise for treating pain, we will briefly mention a few other applications of VR of interest to clinical psychologists. Using VR to treat patients with psychological problems is one of the most promising practical uses of VR technology. For example, VR exposure therapy is proving valuable for treating clinical anxiety disorders. Researchers have recently found VR to be an effective new medium for conducting exposure therapy. Although traditional cognitive-behavioral treatments for specific phobias are successful for those who seek and complete treatment, the vast majority of phobics never seek treatment. VR may allow clinicians to treat a larger proportion of phobics, and there is evidence that phobics find the thought of VR therapy less repulsive than in vivo therapy. Among other disorders, VR exposure therapy has been shown to be effective in treating fear of heights, fear of spiders, fear of flying, claustrophobia, eating disorders, and posttraumatic stress disorder (Garcia-Palacios, Hoffman, Carlin, Furness, & Botella-Arbona, 2002). The illusion of presence in VR and the interactive first-person nature of the experience has been shown to facilitate successful VR exposure therapy (Hoffman, Garcia-Palacios, Carlin, Furness, & Botella-Arbona, 2003), perhaps by eliciting greater activation of fear structures in patients (Foa, & Kozak, 1986). A wide field-of-view fiber-optic image delivery system similar to the one used in the present study has made it possible to give people the illusion of being inside a virtual world while getting an fmri brain scan (Hoffman, Richards, Coda, Richards, & Sharar, 2003). Researchers are beginning to combine VR with fmri brain scans to the study of neural correlates of psychological disorders such as spider phobia (Hoffman, Richards, Carlin, et al., 2003) and to study (e.g., pretreatment vs. posttreatment) the impact of therapy on patterns of fear-related brain activity (Hoffman, Richards, Carlin, et al., 2003). VR is an innovative technology that has a number of valuable applications in clinical psychology worth exploring. Select References/Recommended Readings Campbell, D.T., & Stanley, J.C. (1963). Experimental and quasi-experimental designs for research. Boston: Houghton Mifflin. Carrougher, G.J., Ptacek, J.T., Sharar, S.R., Wiechman, S., Honari, S., Patterson, D.R., & Heimbach, D.M. (2003). Comparison of patient satisfaction and self-reports of pain in adult burninjured patients. Journal of Burn Care and Rehabilitation, 24, 1 8. Cherny, N., Ripamonti, C., Pereira, J., Davis, C., Fallon, M., McQuay, H., Mercadante, S., Pasternak, G., & Ventafridda V. (2001). Strategies to manage the adverse effects of oral morphine: An evidence-based report. Journal of Clinical Oncology, 19, Choiniere, M., Melzack, R., Rondeau, J., Girard, N., & Paquin, M.J. (1989). The pain burns: Characteristics and correlates. Journal of Trauma, 29, Foa, E.B., & Kozak, M.J. (1986). Emotional processing of fear: Exposure to corrective information. Psychological Bulletin, 99, Garcia-Palacios, A., Hoffman, H.G., Carlin, C., Furness, T.A., III, & Botella-Arbona, C. (2002). Virtual reality in the treatment of spider phobia: A controlled study. Behaviour Research and Therapy, 40, Geisser, M.E., Bingham, H.G., & Robinson, M.E. (1995). Pain and anxiety during burn dressing changes: Concordance between patients and nurses ratings and relation to medication administration and patient variables. Journal of Burn Care and Rehabilitation, 16, Hendrix, C., & Barfield, W. (1995). Presence in virtual environments as a function of visual and auditory cues. Proceedings of VRAIS 95 (pp ). IEEE Computer Society. Los Alamitos, CA: Society Press.

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