This study shows the feasibility and acceptability of VR in hospital and home-based settings for people receiving palliative care. Both 3D and 2D platforms were well-tolerated by participants who described positive experiences during and after sessions. Encouragingly, participants reported they would use VR regularly in the future. Given this positive feedback in association with the high completion rates, user comfort, ease of access to affordable VR platforms and encouraging quantitative findings, the estimation of sample size and the prospect of future studies are promising.
Although this feasibility study was not powered to detect differences between groups, our findings indicate that participants with CP report significant decreases in CP intensity during, immediately after and up to 20 minutes after each intervention. However, although linear mixed model analysis showed participants reporting significantly greater levels of presence during 3D HMD VR compared to a 2D screen session, there were no significant differences in reductions of post treatment pain intensity between the two interventions.
Qualitative feedback contributes a deeper evaluation of positive and negative experiences that may explain these findings. First, high levels of user satisfaction engagement and immersion especially using 3D-HMD VR support differences in presence levels between platforms. Second, given the relatively low level of CP intensity at baseline, participants may have had difficulty perceiving changes after each intervention. These latter findings are supported by previous work where more moderate to severe pain at baseline predicts more significant responses to analgesic interventions [30, 31].
Pain-related findings in this study differ to previous work using the same applications and trial protocols in people with spinal cord injury pain (SCI). Here, 3D-HMD VR had significantly greater analgesic effect on SCI pain compared to 2D screen applications (P < .0001) where participants showed over 65% decreases in pain intensity using 3D-HMD VR compared to 43% in this study . The difference in sample-type may account for this variance. Compared to the long-term stability of SCI and neuropathic pain control, our cancer pain sample were older (71.1 ± 14.3 versus 54.3 ± 14.1), at varying stages of advanced disease and fluctuating prescriptions and doses of pain medication prior to the study. Our current sample were frailer and reported fluctuating levels of fatigue, pain severity, confusion and pharmacological symptom control. The SCI sample were also younger, more familiar with computer technology and thus were able to familiarise themselves with devices more quickly. In this current study, participants reported similar enjoyment using the 2D applications where they able to sit close to the screen using the bedside table and not feel confined by the headset.
Our findings among ESAS items for palliative care symptoms showed reductions in tiredness, shortness of breath and mood as well as increases in the feeling of wellbeing using both platforms. However, no significant differences were shown for all ESAS item scores when comparing the effects 3D and 2D interventions. Our findings for 3D-HMD VR are comparable to a previous study using similar technology on people reporting CP. Here, Niki and colleagues investigated the effects of 3D HMD VR (Google Earth®) on symptoms with 20 terminal cancer patients using ESAS as their primary outcome measure. They showed similar findings to our study for all items . Here, both studies report comparably significant reductions in all symptoms except nausea and lack of appetite using 3D-HMD VR. However, given the general symptomatic association between lack of appetite and nausea and the potential for cybersickness these results are explicable.
In the only other study exploring the analgesic effects VR on CP, Mohammad and Ahmed used 3D-HMD VR (Ocean Rift® or a ‘Happy Beach’ scene) plus morphine at peak effect compared to morphine alone on women with breast cancer . Their findings show more significant decreases in pain intensity due to the combined analgesic effects of VR and morphine. The greater effects of VR in combination with another form of analgesia are supported by two previous studies where decreases in SCI pain intensity were greater using 3D-HMD VR plus transcranial direct current stimulation compared to VR alone [34, 35].
The duration of VR analgesia is important. Analgesic actions of VR are separated into two types: distraction and neuroplasticity. Distraction represents short-term attentional diversion away from pain towards an alternative stimulus described as ‘hijacking’ attention, emotion and memory. These effects, depending on the level of presence, may be due to excitability of neuron populations in brain regions associated with pain modulation. Here, healthy participants reporting decreases in pain intensity from painful thermal stimulation during distraction show decreases in thalamic, insular and anterior cingulate cortex activation using functional imaging . Alternatively, neuroplasticity relates to long-term functional and structural changes in neuronal pathways that occur following long-term practice of skills, such as playing a musical instrument or VR use involving interactive real-time simulations of activities. In this study, we investigated only short-term analgesic effects that were assessed during, immediately and up to 20 minutes following each intervention. Attention distraction is the best explanation for the analgesic effect of VR for pain in this population, especially concerning short-term or single session VR use. These immediate effects of VR are shown to be due to temporary activation of top-down pain modulatory pathways via the cingulo-frontal cortex and periaqueductal grey .
Due to COVID-19, study recruitment was slower than anticipated. Encouragingly however, another common reason for non-participation was the successful management of pain on the ward where potential participants did not have pain at the time of assessment for eligibility. However, although the low sample size may have contributed to reduced significance in analgesic effect between the two groups, the size of the effect following 3D-HMD VR (43%) is encouraging and suggests a strong albeit temporary analgesic effect. The significant link between immersiveness and analgesia combined with the findings indicating the significantly greater sense of presence with 3D-HMD VR also supports the potential of 3D-HMD VR to produce analgesia in this setting.
Recruitment was also confounded by the instability of symptoms with advanced disease. Here a participation was planned only for the person to withdraw on the day of the study due to exacerbation of breakthrough symptoms and the effects of pharmacological treatment. Not surprisingly, this was common with people nearing the end of life where only three participated in the trial compared to 10 receiving symptom management. In several instances, family members were not in favour of their relatives participating.
Factors likely to have influenced our findings were the effects of advanced disease and pharmacological treatments on symptoms prior to and during the cross-over trial. Importantly, all participants engaged well with both interventions, however, there were significant differences in levels of concentration and fatigue affecting the completion of self-report measures. Although we only included three short symptom-based questionnaire, participants had difficulty recounting and/or defining symptom severity after both interventions.