People in wheelchairs are limited in their mobility, sensory perception, and activity. These limitations can lead to increased temperature and moisture on the areas that are in contact with the wheelchair surface. These risk factors place wheelchair users at a higher risk for pressure injuries. A pressure injury is localized damage to the skin and underlying soft tissue, usually over a bony prominence or related to a medical or other device. Pressure from medical devices against the skin may also cause pressure injury. Patients with spinal cord injury (SCI) and its associated comorbidities are among the highest-risk population for developing pressure injuries. The incidence of pressure ulcers in patients with SCI is 25%–66%.¹

Wheelchairs: Mechanisms and Pressure Injury Risk

For persons who are wheelchair dependent, the studies have also varied with regard to the results of different surfaces and pressure injuries. Many of the studies were conducted years ago, starting in the 1930s and 1970s to the 1990s. Wheelchair surface types and technology have changed, and the earlier reports may not be entirely applicable to the wheelchair products currently available. Neurotrophic changes, such as those that occur in SCI, result in diminished or absent sensation; thus, the patient is unaware of the pressure overload. Although these neurogenic factors may not be primary in the development of ulcers, the patient is nonetheless prevented from having a normal protective response to the resulting discomfort.²

Support Surfaces Do Not Replace Good Wound Care: Special Populations

In wheelchairs, 50% of the body's weight is supported by 8% of the body on the ischial tuberosities. This configuration places the wheelchair-bound person at risk because of the higher pressure in a smaller area of the body. Studies that have evaluated wheelchair-dependent patients have focused largely on patients with SCI. In one study of 25 persons with SCI and eight persons who did not have SCI, it was also noted that there was more asymmetry in the SCI seating pressures.³

Pressure point impact and ischial tuberosities peak pressure ranged from a low of 39 ± 18 and 68 ± 46 mmHg, respectively, in the fully offloaded cushion to a high of 97 ± 30 and 106 ± 34 mmHg, respectively. In a prospective descriptive cohort study of 24 veterans with SCI from six SCI centers in the Department of Veterans Affairs, veterans with 29 recurrent pressure injuries were observed for nine months.

Additional retrospective medical record data were analyzed for 15 veterans who received inpatient treatment. Most pressure injuries recurred (63%; n = 15 patients) in the same location as the most recent ulcer and at the ischial tuberosities (63%). Mean time to recurrence was 16.6 weeks in the study of veterans. These studies illuminate the chronicity of the wound once a pressure injury occurs. Ragan et al. also reported higher pressure loads of smaller areas for patients in wheelchairs and recommended use of a polyurethane cushion up to 8cm to help redistribute this pressure.⁴ Karatas et al. studied 16 patients with SCI and 18 healthy volunteers.⁵ These investigators also reported that the center of pressure displacement was smaller than in healthy volunteers in all directions (P < 0.05) and that there was no difference in history of pressure injury between patients with high SCI and low SCI.⁵ In a cross-sectional study of 218 persons with SCI, most had pressure injuries (85.7%), whereas 46.3% had multiple surgical procedures for their repair, with 17.5% of pressure injuries that had not healed, mostly on the ischial tuberosities.⁶

Although there have been new developments in technology, their application to appropriate cost-effective interventions is lacking for use in wheelchair-bound persons to prevent pressure injuries. There is a demand to adapt existing tools to aid patients, caregivers, and clinicians to use appropriate intervention strategies to reduce pressure injury in these patients. Evidence-based standards for wheelchair-dependent persons are lacking because of the unique characteristics of persons in wheelchairs and the proliferation of products available for wheelchair surfaces.

Conclusion

The types of pressure redistribution surfaces used with wheelchairs are unknown. Research is needed to understand what pressure points are at risk for pressure injury in wheelchair-dependent persons with current devices. Multiple disciplines in health care and persons who are wheelchair dependent will benefit from further exploration of what current technology for wheelchair surfaces can provide for pressure loads and relief, as well as how pressure points are affected in persons who are dependent on wheelchairs versus those who are not. Guidelines for wheelchair support surface use can be updated based on this information.

References

1. Kruger EA, Pires M, Ngann Y, Sterling M, Rubayi S. Comprehensive management of pressure ulcers in spinal cord injury. Current concepts and future trends. J Spinal Cord Med. 2013;36(6):572-585.

2. Garber SL. Wheelchair cushions: a historical review. Am J Occup Ther. 1985;39(7):453-459.

3. Guitierrrez EM, Alm C, Hultiling C, Saraste H. Measuring seating pressure area, and asymmetry in persons with spinal cord injury. Eur Spine J. 2004;13(4):374-379.

4. Ragan R, Kernozek TW, Bidar M, Matheson JW. Seat-interface pressure on various thicknesses of foam wheelchair cushions: a finite modeling approach. Arch Phys Med Rehabil. 2002;83(6):872-875.

5. Karataş G K, Kapukran A, Kanatl, UCenter-of-pressure displacement during postural changes in relation to pressure ulcers in spinal cord-injured patients. Am J Phys Med Rehabil. 2008;87(3):177-182.

6. Simiya T, Kawamura K, Tokurhiro A, Takechi H, Ogata H. A survey of wheelchair use by paraplegic individuals in Japan part 2; prevalence of pressure sores. Spinal Cord. 1997;35(9):595-8.

About the Author

Ivy Razmus, RN, PhD, CWOCN is an Assistant Professor at the University of Detroit Mercy where she is currently teaching in the BSN Nursing program. Her research focus is on pressure injury prevention for pediatric patients including neonatal patients. She has experience as a Manager of Pediatric populations both neonatal and pediatric intensive care; as a quality analyst within a health system focusing on nursing sensitive quality indicators and root cause analysis; and as a CWOCN in the acute, critical and outpatient settings in the adult population.