Virtual Reality Pain Control During Burn Wound Debridement of Combat-Related Burn Injuries Using Robot-Like Arm Mounted VR Goggles

As the result of frequent use of explosive devices against US troops by enemy insurgents in Iraq and Afghanistan, thousands of US military personnel have suffered severe burn wounds and/or other trauma injuries. Malchow and Black1 cite personal reports that more than 80% of American casualties are transported from Baghdad to Germany with uncontrolled pain. Based on military medical records, Holbrook et al.2 found that 39% of posttraumatic stress disorder (PTSD)-positive and 24% of PTSD-negative injured military personnel received no morphine during resuscitation and early trauma care. Even with use of powerful pharmacologic analgesics, severe-to-excruciating pain often continues during hospitalization due to medical procedures. US casualties with severe combat-related blast injuries, such as burned hands, amputations, and multiple traumatic injuries, must undergo frequent wound care/rehabilitation sessions as part of their recovery. For patients with severe burns, wound care/debridement typically involves cleaning the wound and scrubbing dead skin away as it sloughs off the wound during healing, to help avoid infection. Debridement typically occurs daily, for weeks or months. Burned skin naturally contracts as it heals. Physical therapy stretches help to counteract contraction, increasing skin elasticity, and enhancing range of motion.3 Although pharmacological agents can usually control pain while patients are resting with little or no movement, most burn patients report severe to excruciating pain during medical procedures such as wound cleaning and physical therapy.4 Although opioids are the cornerstone analgesic for patients with severe burn injuries and other trauma injuries,1,5 side effects of opioid narcotic analgesics limit dose levels and frequency of use.6 Opioid side effects frequently include nausea and constipation, and opioids may cause immunosup-pression.7 Patients often experience gradually reduced analgesic effects with repeated administration of opioids, a phenomenon known as tolerance. In other words, with frequent medications over days, weeks or months, escalating doses of opioid analgesics are needed to achieve the same analgesic effect. And over time, daily use of opioids is frequently accompanied by physical dependence, the need for continued drug use to prevent physical and emotional withdrawal symptoms.8 At high doses, opioid side effects pose a significant challenge to medical providers trying to management acute pain during daily severe burn wound medical procedures.1,6 In an effort to reduce opioid usage, ketamine may be given for its opioid sparing effects.9 Used at low doses, ketamine is a non-barbiturate intravenous anesthetic that is used as part of a multi-modal therapy. Ketamine does not cause respiratory depression, but ketamine is associated with psychoactive effects (e.g., dissociative and psychotic states).10 Pain is often self-reported as a number on a scale. The validity of Graphic Rating Scale (GRS) subjective measure of pain intensity has been demonstrated by their strong associations with other measures of pain intensity (e.g., changes in pain-related brain activity during functional magnetic resonance imaging [fMRI] brain scans, which measures changes in blood flow related to neuronal activity)11,12 and through their ability to detect treatment effects. The word GRS has also demonstrated convergent validity, and strong test-retest reliability.13 Previous studies indicate that Virtual Reality (VR) distraction can affect all of the components of pain measured in the present study, and that the GRS used in this study is sensitive to these effects.14 Solving the problem of excessive pain may prove more challenging in military populations than in civilian populations. Both physical and emotional suffering, including PTSD and depression, are particularly problematic in survivors of combat-related injuries caused by explosions. In one recent study,15 patients who had experienced combat-related blasts had more extensive physical injuries (i.e., they were more likely to have amputations) and used higher levels of opioid analgesics. Patients with combat-related blast injuries showed significantly less improvement in pain severity (10% reduction) as a function of treatment/hospitalization than either combat/non-blast (43% reduction) or non-combat (53% reduction) groups. And servicemen with blast-related injuries showed much higher rates of PTSD than those injured via other means.15 Alternatives to pharmacological agents are needed and one such method is immersive VR. Controlled studies with civilians show preliminary evidence that allowing patients to “go into” VR during painful procedures can help to reduce excessive pain nonpharmacologically. Compared with standard of care (i.e., pain medications with no VR) researchers consistently find 30% to 50% reductions in pain ratings when VR is used adjunctively with opioids during civilian severe burn wound care14,16 and physical therapy.17 In addition, analog laboratory studies using fMRI brain scans have shown large reductions in pain-related brain activity associated with VR analgesia.11 Immersive VR has the potential to decrease suffering for US casualties with combat-related burn injuries who must undergo frequent (e.g., daily) painful wound de-bridement and rehabilitative procedures. VR is typically used adjunctively, in addition to any pain medications the patient is already receiving. One case study has recently reported VR analgesia while treating soldiers with combat-related burn injuries,18 but to date no controlled studies on this important topic have been published. Immersive VR is hypothesized to reduce pain via a non-pharmacologic attentional mechanism.11 Patients look into VR goggles which block patients' view of the hospital room so they cannot see the wound care. The goggles substitute the real world with synthetic computer-generated images from an illusory 3D virtual world of SnowWorld. Noise canceling earphones block sounds from the hospital room, and substitute more calming music and sound effects. The patient interacts with the virtual world, throwing snowballs at objects in the virtual world by clicking a mouse button, this makes it even more interactive and effective.19,20 SnowWorld is a 3D computer graphic system that uses the imagery of an icy canyon with a river flowing through it as a backdrop for snowmen, penguins, woolly mammoth, fish, and snowfall. The object of the system is to distract the patient by allowing the participant to focus on throwing snowballs at objects within the canyon while moving through the canyon. The snowmen freeze with one snowball hit and shatter with two hits. The white and blue colors are soothing and the snowy images are the opposite of the hot burn that resulted in their injuries. Pain requires attention,21 and patients have a limited amount of attention available. VR draws upon these limited controlled attentional resources, leaving less attention available to process incoming pain signals. Consistent with the involvement of an attentional mechanism, burn ss report spending much less time thinking about their pain during wound care while in SnowWorld.14,16,18 In addition, laboratory pain studies have shown that on a divided attention task, where the primary task is to monitor a string of numbers, performance on the primary task dropped significantly when participants went into VR.22 And, there appears to be a dose-response relationship between the physical properties of the VR system (immersiveness) and the amount VR reduces pain.19,20 In contrast, opioids work by reducing transmission of neural nociceptive signals. Exposing receptors to opioids inhibits neuronal signaling, and reduces the number of noci-ceptive signals transmitted from the pain receptors to the brain.1 More recently, laboratory studies involving brief thermal pain stimuli in healthy volunteers undergoing VR during fMRI found the amount of pain reduction and associated reduction in pain related brain activity were comparable to analgesia from a moderate dose of hydromorphone.12 The largest decreases in pain and pain-related brain activity were observed when VR and opioids were combined.12 This approach capitalizes on the combined analgesic action of the two treatment modalities (pharmacologic vs. VR), each thought to reduce pain via different mechanisms. The present study explored for the first time (1) whether adjunctive VR can reduce pain in military patients with combat-related blast severe burn injuries, (2) the use a robotlike arm mounted (helmet-less) VR system designed to reduce barriers to using VR with combat-related burn patients (e.g., face and head injuries, discomfort), and (3) whether soldiers reporting the highest pain levels during wound care still benefited from adjunctive VR. It measured whether VR could reduce pain in an unusually challenging patient population: military patients with severe pain intensity and whether patients reporting the highest pain levels benefited as much as patients experiencing more moderate procedural pain levels.