September 14, 2022 | Net Health

7 min read

Pressure Injury Prevention: Recognizing the Early Signs of Injury

This blog originally appeared in the November 2021 issue of Wound Source Practice Accelerator, sponsored by Net Health. Reprinted with permission. 

Here’s a question for you: How long does it take for a pressure injury (PI) to form? Do you think it happens in 30 minutes? Two hours? Eight hours? The answer is all of the above. The time it takes for a PI to develop depends on a number of different factors, which we will discuss here. This blog will describe how a PI forms, some signs that a PI is forming, and how to assess a patient’s skin for a PI. It will then look at some types of intervention and assessment that help in the prevention and treatment of a PI and track its healing or declination.

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Development of a Pressure Injury

Just as all patients are unique, so are their wounds. Clinicians must consider multiple risk factors and the type of pressure to which the patient is exposed. The length of time a PI takes to develop is variable based on some of these factors.

A PI typically occurs when there is a source of unrelieved pressure that leads to disruption and eventual breakdown of the skin’s integrity.1 If a patient is exposed to unrelieved pressure, their underlying tissue, such as the skin, soft tissue, muscle, and bone, exert an outward force against the external element causing the pressure. Imagine what you naturally do if you are left to sit in a hard wooden chair for a long time. You naturally shift positions frequently, probably not even realizing that you are doing so. Now picture an immobile patient sitting in that same hard wooden chair with decreased sensation.

As time passes, the bones of their pelvis press into the hard seat of the chair. The bone presses against the muscle, soft tissue, delicate blood vessels, and skin between it and the chair. This pressure can eventually cause the capillaries feeding the areas to become occluded, and necrosis from the lack of blood flow to the tissue can occur. In this instance, we may see the following sequence of events:

  • Hyperemia (redness within 30 minutes)
  • Erythema (deep redness): within 2 hours
  • Tissue ischemia (compromised circulation): within 2 to 6 hours
  • Tissue necrosis (tissue death): in 6+ hours

However, a PI may occur in as little as 30 minutes when the patient is exposed to higher amounts of pressure. For example, a patient lying on a hard table in the operating room may show signs of PI development in as little as 30 minutes if the table isn’t properly padded.

A PI is more likely to occur over a bony prominence. Some areas that are more at risk may vary depending on the position. For example, if a patient sleeps on their side, they may be putting pressure on their toes, ankle, knee, hip, shoulder, or ear. If they are lying on their back, some areas at risk may include their heels, coccyx, elbow, shoulder blade, or the back of their head. And if seated, some areas at risk may include the shoulder blade, coccyx, hip, ischium, or heels.

Friction and shearing forces can also cause a PI to develop. This can occur with sliding forces. Let’s consider how this can happen. Imagine your patient is in their bed. The head of the bed is at a 45-degree angle, so over time, they slide downward. Perhaps their skin is slightly sweaty and sticks to the sheet. In this scenario, as the heavier bones (such as the bones of the pelvis) slide downward with gravity, the skin remains upward. These two forces in the opposite direction cause the epidermal and the dermal layers of the skin to separate. This can tear the delicate capillaries within this tissue and lead to impaired perfusion, putting this patient at increased risk of developing a PI.

Assessing for the Formation of a Pressure Injury

Becoming a savvy wound care clinician does take a bit of detective work and fine-tuning of one’s assessment skills, particularly when assessing a patient’s risk of developing a PI and what the early stages of a PI look like. There are multiple risk factors that should be considered when determining whether a patient is at risk. These risk factors include immobility, decreased or absent sensation, diabetes, vascular disease, malnutrition, incontinence, poor positioning, and many others.2

According to the Agency for Healthcare Research and Quality (AHRQ), a comprehensive skin assessment can be used to identify, prevent, and treat PIs.3 This assessment entails a head-to-toe physical examination requiring the clinician to look at and feel the skin, particularly the areas over a bony prominence. During this exam, the clinician should identify any current pressure injuries, sites of erythema (either blanching or non-blanching), and any other lesions or skin-related factors, such as rashes, dehydrated skin, or the presence of moisture-associated skin damage.3

To conduct an assessment, a clinician will first ensure that the patient is comfortable and try to minimize exposed body areas. They will make sure there is adequate lighting during the exam and use a blanket or towel, if possible, to protect the patient’s privacy. A wound care professional will examine the patient’s back, so if the patient is unable to reposition themself, the professional must ensure that they have help. While wearing gloves, the clinician may assess the following five factors:

  • Temperature
  • Color
  • Moisture level
  • Turgor
  • Skin integrity

Clinicians make sure that they examine any areas of skin under medical devices, such as tubing or catheters. If a patient requires oxygen, clinicians observe the nares for possible trauma from the tubing. If a patient is too unstable to turn properly, such as patients in critical care units, wound care professionals make sure that they document this. Assessments are done on admission and then repeated regularly to ensure that there have been no changes. The frequency of assessments may vary depending on the patient, the setting, and their specific risk factors. This may also be incorporated into other tasks, such as cleaning, bathing, or turning the patient.3

Assessing Darker-Skinned Patients

When assessing a patient for developing erythema, clinicians are aware that a darker-skinned patient may not show the classic erythema that a lighter-skinned patient might. Instead, they look for changes in heat, edema, induration, or pain (if present). It’s important to look for a difference in color in the area compared with the patient’s typical skin color. A developing injury may appear to have a purple/blue/violet hue. Putting pressure over an area should normally cause it to blanch, and if this doesn’t occur, this is a good clue that the patient may be developing an injury.4

Intervention Tools and Methods

Knowing a patient’s risk factors and completing a thorough skin assessment are the first parts of creating a successful PI treatment program. With this knowledge, one can now intervene to prevent a PI from forming or tracking and treating a PI that already exists.


We are firmly planted in a digital world; clinicians can utilize this when conducting assessments for PIs. A 2020 systemic review found multiple types of bedside devices that can enhance the early detection of a PI.5 These included ultrasound, thermography, subepidermal moisture measurement, and laser Doppler.

These technologies all come with their own merits and limitations, but they do provide the clinician with an assist when it comes to assessing and tracking PIs. A clinician may also use Web-based programs and data-tracking tools that may help with proper documentation and data analysis. Ultimately, these tools are just that—tools that savvy clinicians can put in their arsenal of tricks when it comes to PI assessment and prevention.


1Al Aboud AM, Manna B. Wound pressure injury management. In: StatPearls. StatPearls Publishing; 2021. Accessed November 18, 2021.

2Agrawal K, Chauhan N. Pressure ulcers: back to the basics. Indian J Plast Surg. 2012;45(2):244–254.

3Agency for Healthcare Research and Quality (AHRQ). Preventing pressure ulcers in hospitals. 2011; reviewed 2014. Accessed November 1, 2021.…

4Clark M. Skin assessment in dark pigmented skin: a challenge in pressure ulcer prevention. Nurs Times. 2010;106:30. Accessed November 1, 2021.…

5Scafide K, Narayan MC, Arundel L. Bedside technologies to enhance the early detection of pressure injuries. J Wound Ostomy Continence Nurs. 2020;47(2):128-136.

The views and opinions expressed in this blog are solely those of the author, and do not represent the views of WoundSource, HMP Global, its affiliates, or subsidiary companies.

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