In the past, I have written about wheelchair cushions and how materials and product design affect skin protection. This month, I would like to focus on weight shifting and its role in skin protection.
Before we address the impact of weight shifting on pressure management, let’s have a brief review of what happens to our bodies when we sit, assuming we are sitting with a neutral pelvis; that is, that the pelvis is not tilted anteriorly or posteriorly. When we sit with a neutral pelvis, the ischial tuberosities are the lowest point on the pelvis. As we sit, our bodies react with gravity and the fat and muscle directly beneath the ischial tuberosities slowly move away from the point below the ischia, causing the ischial tuberosities to be closer to the skin. As we sit, this condition continues. After time, the pressure experienced by the skin under the ischial tuberosities causes the capillaries to close, resulting in the skin cells beginning to die due to lack of oxygen and nutrients. This can occur in as little as 10 to 15 minutes if there has been no weight shifting (Semble, 1994). As we continue to sit, the soft tissue continues to spread and the bony contact area increases. The greater trochanters may also begin to experience pressure. Discomfort will occur in about 30 minutes (Semble, 1994). This reaction of our bodies to gravity explains why when we are seated on a hard chair or a thin cushion for a period of time we begin to experience discomfort (assuming we are sensate) and find ourselves shifting and changing position to relieve the pressure. Think about the last time you were on a long car ride or plane ride or the last time you sat down all day for a full-day education workshop. You likely changed position in response to any discomfort you were experiencing without consciously thinking about it.
What about people who are at risk for pressure ulcer development? How often should they change position or shift weight? The European Pressure Ulcer Advisory Panel and National Pressure Ulcer Advisory Panel, in their Pressure Ulcer Prevention Quick Reference Guide, recommends limiting “the time an individual spends seated in a chair without pressure relief” (2009, p. 18). Of course, posture and the surface on which a person sits also will affect pressure and possible pressure ulcer development. The Quick Reference Guide recommends using a “pressure-redistributing” cushion for individuals who are mobility-impaired and at risk for pressure ulcer development (The European Pressure Ulcer Advisory Panel and National Pressure Ulcer Advisory Panel, 2009, p. 21). (As seating is beyond the scope of this month’s article, please refer to my previous articles on Skin Protection and Cushion Materials and Cushion Design, respectively, for more information.)
No matter how ideal the cushion materials and design may be for skin protection, periodic weight shifting must occur to relieve pressure. All at-risk individuals should be repositioned to reduce the duration and magnitude of pressure as “high pressures over bony prominences, for a short period of time, and low pressures over bony prominences, for a long period of time, are equally damaging. In order to lessen the individual’s risk of pressure ulcer development, it is important to reduce the time and the amount of pressure she/he is exposed to.” (European Pressure Ulcer Advisory Panel and National Pressure Ulcer Advisory Panel, 2009, p. 16).
How often should repositioning occur? The joint Pressure Ulcer Advisory Panel referenced above does not specify a frequency of repositioning; rather, they suggest that the frequency of repositioning will be dependent upon individual factors, such as tissue tolerance, level of activity, medical condition, and upon the support surface used (p. 17).
Another source of information regarding the frequency of repositioning required is the Pressure Ulcer Prevention and Treatment Following Spinal Cord Injury: A Clinical Practice Guideline for Health-Care Professionals. This guideline recommends weight shifting “every 30 minutes for 30 seconds or every 60 minutes for 1 minute to allow reoxygenation of the cutaneous tissues” (Consortium for Spinal Cord Medicine, 2000, p. 59). A variety of techniques can be used for weight shifting, including a full push-up, a lateral lean, a forward lean or a power repositioning feature on a power wheelchair. For a dependent sitter who does not have the physical or mechanical means to weight shift independently, the guideline recommends to “reposition the wheelchair-seated individual at least every hour; if this is not possible and the individual is unable to perform weight shifts, return the individual to bed” (Consortium for Spinal Cord Medicine, 2000, p. 4).
A more recent guideline, The Canadian Best Practice Guidelines for the Prevention and Management of Pressure Ulcers in People with Spinal Cord Injury: A Resource Handbook for Clinicians, goes further with its recommendation and states that “a pressure relieving movement must be at least 1 to 2 minutes in duration” (Houghton, Campbell and CPG Panel, 2013, p. 141).
Like the Pressure Ulcer Prevention Quick Reference Guide, the Canadian guideline recommends individualized weight shifting strategies. Strategies include not only the deliberate pressure relieving movements of push-ups and leaning, but also the inherent weight shifting that occurs with functional movement when completing activities of daily living. The use of dynamic positioning features, such as tilt and recline, is recommended when a person is unable to perform effective weight shifts independently. The frequency and duration of weight shifts that is recommended will be dependent upon the person’s response to the strategy over the course of the day. For example, is fatigue a factor at the end of the day that limits the effectiveness of the weight shifting strategy used earlier in the day? Should another strategy be employed? Whatever weight shifting regime is found to be effective for an individual, the results should be documented, including the frequency, duration and position.
As always, please provide your comments, questions and suggestions regarding Clinical Corner on my blog. I look forward to hearing from you!
Sheilagh Sherman, BA, BHScOT, OT Reg. (Ont.)
Sunrise Medical Canada
Note: The content of this article is not meant to be prescriptive; rather, it is meant as a general resource for clinicians to then use clinical reasoning skills to determine optimal seating and mobility solutions for individual clients. Sheilagh is unable to answer questions from members of the general public. Members of the general public are directed to their own therapists or other health care professionals to ask questions regarding seating and mobility needs.
This article is © Sunrise Medical, Inc., 2013 and cannot be copied, distributed, or otherwise reproduced in whole or in part without the express written permission of Sunrise Medical Canada.
Consortium for Spinal Cord Medicine. (2000). Pressure ulcer prevention and treatment following spinal cord injury: a clinical practice guideline for health-care professionals. Paralyzed Veterans of America.
European Pressure Ulcer Advisory Panel and National Pressure Ulcer Advisory Panel. (2009). Prevention and treatment of pressure ulcers: quick reference guide. Washington DC: National Pressure Ulcer Advisory Panel.
Houghton P.E., Campbell K.E., and CPG Panel. (2013). Canadian Best Practice Guidelines for the Prevention and Management of Pressure Ulcers in People with Spinal Cord Injury. A resource handbook for Clinicians. Ontario Neurotrauma Foundation. Accessed at http://www.onf.org
Semble, J.A. (1994). The Biomechanical Relationship of seat design to human anatomy. In R. Lueder & K. Noro (Eds.), Hard Facts about Soft Machines. The Ergonomics of Seating (pp. 221-230). Encino, CA: Taylor & Francis.