Introduction

According to the National Pressure Injury Advisory Panel (NPIAP) definition, “A pressure injury is localized injury to the skin and/or underlying tissue usually over a bony prominence, as a result of pressure, or pressure in combination with shear and/or friction.”¹ Pressure injuries are an unfortunate and all too frequent occurrence, despite being preventable. It is estimated that approximately 2.5 million hospitalizations in the United States are due to pressure injuries.² According to research by the NPIAP, up to 40% of patients will develop a pressure injury while in critical care units.³ However, a clinician can assist in preventing these pressure injuries by understanding which anatomic areas are most at risk.

Key Anatomic Areas Associated With Pressure Injury Development

Specific areas of the body are more likely to develop a pressure injury, depending on the position of the patient. When patients are in a supine position, the following areas are at risk:

• Posterior heels
• Sacrum
• Elbows
• Shoulder blades
• Back of the head

When a patient is lying on their side, at-risk areas include the medial and lateral malleoli, the medial and lateral aspects of the knees, the hips, shoulders, and ears. While seated, patients are more likely to develop pressure injuries at their shoulder blades, sacrum, ischia, feet, and posterior knees.⁴ Risk factors for the development of pressure injuries are numerous and include the following¹:

• Immobilization
• Nutritional status
• Motor or cognitive impairment
• Diabetes
• Severe illness
• Sensory deficit
• Skin fragility
• Incontinence
• Reduced perfusion
• Recent fracture
• Edema
• The presence of bony prominences
• Use of pressure-causing medical devices

Pressure injury scales, like the Braden Pressure Injury Risk Assessment, consider sensory perception, moisture, activity, mobility, friction, and shear as risk factors. They are used to identify not only who is at risk but also the degree of risk. While such risk assessment scales are widely used and accepted, these scales seem to neglect patient weight as a contributing factor.

Pressure Injury Considerations Related to Patient Weight

Recently, wound care researchers have begun investigating areas where special consideration should be given to patients who are considered over or underweight to prevent pressure injury development. A 2011 study concluded that the body mass index (BMI) is not a predictor for heel pressure ulcer development, as BMI level seems unrelated to developing heel pressure ulcers.⁵ Further, this study’s findings supported that “the etiology and pathogenetic mechanisms of trunk and heel PU development might be partially different.”⁵ As a result, pressure ulcer models may need to be redesigned due to the specific risk factors that pertain to a distinct location. In 2014, a study of BMI and pressure ulcers noted that “BMI and the incidence of pressure ulcers were related in ICU patients. Underweight and extremely obese patients were at higher risk for pressure ulcers than were normal weight or obese patients. If a patient has an extremely low or extremely high BMI, additional care to prevent pressure ulcers is desirable.”⁶ A more recent systematic review and meta-analysis from 2021 found that risk of pressure injury development was not significantly higher in patients with obesity and morbid obesity as opposed to populations at more normal weights. In fact, patients considered overweight were found to have a lower risk of pressure injury development compared to patients deemed underweight, who are the most at risk.⁷ Interestingly, all 3 studies identified those with lower weights as at higher risk for pressure injury development.^6,5,7 Although pressure injuries at certain anatomical locations seem to develop regardless of BMI (like heel PIs), pressure injuries found within the sacral and trunk areas can vary in severity in relation to BMI. Therefore, wound care professionals must familiarize themselves with best practices to prevent and treat pressure injuries in patients at either end of the BMI spectrum, although patients considered underweight may warrant even further consideration.

Risks for Patients With High BMI

Obesity is associated with multiple factors that may contribute to the patient forming rashes, wounds, infection, and impaired healing. In patients considered obese, the potential presence of heavy skin flaps and greater skin surface area can lead to increased pressure at specific, otherwise atypical, regions of the body.⁹ These areas include the following⁴:

• Abdomen (panniculus)
• Axilla
• Breasts
• Occiput
• Hips
• Trunk
• Torso

Comprehensive pressure injury prevention for patients with a high BMI should include risk assessment specific to obesity, referral for nutritional assessment and management, assessment of skin folds, preventative skin care, assessment of the potential need for medical equipment and devices for bariatric use, pressure redistribution support surfaces, bed systems with advanced microclimate technology, and regular repositioning while encouraging early mobilization.⁸ The risk of infection and shearing at skin folds can be minimized with interventions such as twice daily cleansings and the use of skin emollients. Increased pressure at skin folds can be reduced using prophylactic dressings, such as those made from soft absorbent foam and those with moisture wicking features. Bariatric sliding sheets can reduce shearing forces during patient repositioning.

Risks for Patients With Low BMI

As mentioned previously, poor nutritional status, especially within the aging population, is a major risk factor for pressure injury development. In fact, malnutrition affects approximately 30-50% of those within the inpatient setting.¹⁰ A patient is considered malnourished if their BMI is less than 20 and underweight if their BMI is less than 18.5.¹⁰ Protein-calorie malnutrition (PCM) weakens a patient's skin and, subsequently, its ability to heal.¹¹ The weakened status of an underweight patient’s skin makes it all the more important that specific, exposed areas of the body are properly inspected and offloaded. Patients who are considered underweight may suffer from increased pressure in the following areas⁴:

• Sacrum
• Ischial tuberosity
• Trochanters
• Shoulders

In patients with especially low weights, these areas may be void of standard fatty overlay and become more prominent, leading to increased pressure and/or shear having an impact. These resultant forces on the patient's skin make it even more important that specific, exposed, or unprotected areas of the body are properly inspected and offloaded.¹²

Pressure Injury Prevention and Management Technology

For patients considered over or underweight, prophylactic dressings or similarly protective or padded foam dressings used during PI treatment can help to reduce friction, minimize shear, redistribute pressure, and maintain an optimal microclimate. A clinician can often pre-cut such dressings into convenient shapes for application over at-risk areas, such as the sacrum and heels, and these dressings can also often be hand-cut to fit under medical devices.¹³ Offloading heel protectors may help to elevate the patient’s heels. Mattress overlays used to cover the entire surface, or isolated areas of an existing standard mattress can also reduce friction and shear. Intelligent pressure management systems may assist in controlling mattress pressures in both active (alternating) and reactive (constant low pressure) therapy modes. Microprocessors regularly assess the body mass distribution of patients and only read cell pressures to suit their individual needs. Advanced foam mattresses that combine various foam densities for functionality can also be employed.¹³ Especially for admitted patients, inadequate bed or wheelchair size for a patient’s body habitus may directly lead to pressure injury, as may a lack of suitable lifting devices. Remote patient monitoring systems may also be a vital tool to assist care teams in executing proper offloading measures such as patient turning.

Conclusion

Whether a patient has a high or low BMI, this factor is not traditionally incorporated into pressure injury risk assessment tools. Yet, BMI should nevertheless be considered when formulating individualized preventative care plans. Devices such as prophylactic dressings, remote patient monitoring technology, offloading apparatuses, and properly sized medical furniture and equipment can aid in the offloading of BMI-specific at-risk areas.

References

1. Edsberg LE, Black JM, Goldberg M, McNichol L, Moore L, Sieggreen M. Revised National Pressure Ulcer Advisory Panel Pressure Injury Staging System: Revised Pressure Injury Staging System. J Wound Ostomy Continence Nurs. 2016;43(6), 585-597. doi:10.1097/won.0000000000000281
2. Kottner J, Dassen T. Pressure ulcer risk assessment in critical care: Interrater reliability and validity studies of the Braden and Waterlow scales and subjective ratings in two intensive care units. Int J Nurs Stud. 2010;47:671–7. doi:10.1016/j.ijnurstu.2009.11.005
3. Pressure ulcers in America: prevalence, incidence, and implications for the future. An executive summary of the National Pressure Ulcer Advisory Panel monograph. Adv Skin Wound Care. 2001;14(4):208–15. doi:10.1097/00129334-200107000-00015
4. SCI Model System Dissemination Committee. Areas at high risk of developing pressure sores. Model Systems Knowledge Translation Center. Accessed October 1, 2022. https://msktc.org/sci/factsheets/skincare/Areas-of-the-Body-at-High-Ris…
5. Kottner J, Gefen A, Lahmann N. Weight and pressure ulcer occurrence: a secondary data analysis. Int J Nurs Stud. 2011;48(11):1339-1348. doi:10.1016/j.ijnurstu.2011.04.011
6. Hyun S, Li X, Vermillion B, et al. Body mass index and pressure ulcers: improved predictability of pressure ulcers in intensive care patients. Am J Crit Care. 2014;23(6):494-501. doi:10.4037/ajcc2014535
7. Alipoor E, Mehrdadi P, Yaseri M, Hosseinzadeh-Attar MJ. Association of overweight and obesity with the prevalence and incidence of pressure ulcers: A systematic review and meta-analysis. Clin Nutr. Published August 13, 2021. Accessed September 26, 2022. https://www.clinicalnutritionjournal.com/article/S0261-5614(21)00377-0/…
8. Haesler E. Evidence Summary: Prevention of pressure injuries in individuals with overweight or obesity. Cambridge Media Journals. https://journals.cambridgemedia.com.au/wpr/volume-26-number-3/evidence-…. Published April 2018. Accessed September 26, 2022.
9. Neloska L, Damevska K, Nikolchev A, Pavleska L, Petreska-Zovic B, Kostov M. The Association between Malnutrition and Pressure Ulcers in Elderly in Long-Term Care Facility. Maced J Med Sci. 2016;4(3):423-7. doi:https://doi.org/10.3889/oamjms.2016.094
10. Haesler E. Evidence summary: Prevention of pressure injuries in individuals with overweight or obesity. Wound Practice and Research Wounds Australia Journal
11. Munoz N, Litchford M, Cox J, Nelson J, Nie Ann, Delmore B. Malnutrition and Pressure Injury Risk in Vulnerable Populations: Application of the 2019 International Clinical Practice Guideline. Adv Skin Wound Care. 2022;35(3):156-165. doi:10.1097/01.ASW.0000816332.60024.05
12. Kottner J, Gefen A, Lahmann N. Weight and pressure ulcer occurrence: a secondary data analysis. Int J Nurs Stud. 2011 Nov;48(11):1339-48. doi: 10.1016/j.ijnurstu.2011.04.011. Epub 2011 May 23. PMID: 21601854.
13. Reddy M, Gill SS, Rochon PA. Preventing pressure ulcers: a systematic review. JAMA. 2006 Aug 23;296(8):974-84. doi: 10.1001/jama.296.8.974. PMID: 16926357.