Most of us don’t have to worry about pressure ulcers, or “bed sores.” But for people who stay in the same position for long periods of time without shifting their weight or repositioning themselves — such as wheelchair users and those confined to bed due to an injury or surgery — they’re a very serious concern. In Canada, the prevalence of pressure ulcers is estimated to be 25.1 per cent in acute care hospitals and 29.9 per cent in long-term care facilities. Once pressure ulcers form, they can be hard to treat and can lead to severe medical complications, including infection, sepsis, and death. Therefore, health care providers try to prevent them from developing in the first place by regularly repositioning their patients, choosing support surfaces (beds and chairs) that might reduce or redistribute pressure on areas of the body most susceptible to skin and tissue damage, and inspecting skin regularly for signs of damage. However, despite these measures, pressure ulcers remain common in at-risk individuals, leading health care providers to seek better ways to prevent them. Over the years, CADTH has looked at what the evidence says about the effectiveness of some of the preventive technologies. CADTH is an independent agency that finds, assesses, and summarizes the research on drugs, medical devices, and procedures to help Canadian health care decision-makers. In 2015, CADTH looked for evidence specifically related to people who use wheelchairs. One review, focused on wheelchair selection, found evidence that points to the importance of a formal assessment of a patient’s unique physical attributes and lifestyle when choosing a wheelchair. The second review, which looked at evidence-based guidelines for pressure ulcer prevention, found that, in addition to individualized assessments, measures related to education and self-management; weight management and nutrition; pressure mapping; proper bed positioning and patient repositioning; and mobility, activity, and conditioning are recommended. For patients with limited mobility confined to beds, repositioning is an important aspect of pressure ulcer prevention. Repositioning can be performed manually, but special turning devices are available to help health care providers reposition patients more easily and more regularly. Similarly, “positioning chairs” are available that allow for frequent repositioning of seated patients and can be either designed as wheelchairs or, for more mobile individuals who sit for long periods of time, stationary chairs. CADTH looked for evidence of the effectiveness of turning devices in 2013 and of positioning chairs in 2017 but found that no studies had yet been published. Materials such as incontinence underpads (also called soaker pads) and natural sheepskins are sometimes placed on top of a patient’s bed or other support surface in an attempt to prevent pressure ulcers. CADTH looked into both these interventions in 2017. No evidence was found on the effectiveness of incontinence underpads; however, if they are to be used, disposable underpads might result in significantly fewer pressure ulcers than the reusable variety, according to a CADTH review of the evidence comparing the two. CADTH’s review of natural sheepskins found low-quality evidence suggesting that they might reduce the risk of pressure ulcers although some patients might find the woolly sheepskins too warm. In addition to the established methods for preventing pressure ulcers, there are some newer interventions. Used in patients with spinal cord injuries, electrical muscle stimulation delivers periodic electrical pulses to the buttock muscles in an attempt to simulate the subconscious fidgeting and shifts in body position that those without mobility issues make. A 2016 CADTH review found that it isn’t yet clear if this technology is effective.