An eschar is an injury caused by constant pressure in a certain area of the body that causes damage to the underlying tissue. Soft tissue ischemia is produced by compression between two rigid structures, which are the bone and outer surface.

There are many terms used to refer to them: eschars, bed sores and pressure ulcers. Not all of these ulcers are caused by decubitus or by being bedridden, so the most appropriate term is pressure ulcers.

These lesions are commonly located in areas surrounding the bony prominences: occiput, scapula, elbows, sacrum, ircuster, ischium, knees, ankles, heels. 95% of the injuries occur under the umbilicus and 75% in the pelvic area.

According to the US Department of Health and Human Services, the classification of the ulcer is based on the depth and type of tissue involved:

  • Grade I: persistent erythema, edema, depigmentation, local heat or induration of the skin without ulceration.
  • Grade II: partial thickness skin loss involving epidermis, dermis or both. Surface ulcer type abrasion or vesicle.
  • Grade III: deep ulcer with variable subcutaneous cellular tissue involvement.
  • Grade IV: cutaneous loss of complete thickness that extends to the muscular, bone or support structures (for example: tendons, joints).


The production of a pressure ulcer is determined by the application of pressure and the reduction of tissue tolerance mediated by intrinsic and extrinsic factors.

  1. The pressure

– Intensity: it must exceed the capillary pressure of the tissues (32 mmHg), which would produce ischemia, cell death and ulceration.

– Duration: inverse parabolic relation between pressure and time. The longer the pressure is applied, the lower the pressure necessary to generate an ulcer.

– Effect: hypoxia and thrombosis at the level of the microcirculation.

  1. Tissue tolerance

– In addition to the mechanism of ischemia-pressure, there are multiple factors that contribute to the process, decreasing tissue tolerance and creating the conditions for the ulcer to be generated. These factors can be extrinsic or intrinsic.

– Extrinsic factors (external to the patient)

  1. Maceration, incontinence, perspiration, exudate from the wound produce excess moisture in the skin, making it softer and susceptible to injury.
  2. Friction: rubbing with another surface damages the epidermis and causes superficial abrasions.
  3. Cutting forces or shearing: friction in combination with gravity moves the soft tissue over a fixed bone producing vessel disruption, which generates more ischemia.

– Intrinsic factors (determined by the patient)

  1. Age: in older patients, the skin is drier, less elastic and with a reduction in tissue mass that favors ulceration.
  2. Nutrition: low oral intake or malnutrition favor the production of these ulcers.
  3. Mobility: Paralysis, sensory disorders, extreme weakness, apathy, lack of mental alertness and excessive sedation affect movement.
  4. Tissue hypoxia: any disorder that results in tissue hypoxia also favors the genesis of these ulcers. Among these disorders are circulatory or respiratory alterations, anemia and edema.
  5. Hygiene: lack of hygiene increases the number of microorganisms in the skin, maceration and makes it more prone to injury.
  6. Spinal injuries, neurological diseases, such as spasticity.
  7. Others: anemia, hyporoteinemia, hypovitaminosis, drug addiction, associated psychiatric pathology, respiratory pathology, self-destructive symptoms, chronic infections, urinary pathology, digestive, family abandonment, bone and joint pathologies.

The best treatment for eschar is prevention, because once the ulcer develops, it only has a 10% chance of complete healing.

These are some prevention measures:

  • Recognize the patient at risk
  • Decrease the effects of pressure
  • Evaluate and improve nutritional status
  • Preserve the integrity of the skin
  • Massify care standards for these patients throughout the hospital

Why treatment in hyperbaric chamber can help treat eschar?

The increase of oxygen in the blood reached by the hyperbaric chamber is anti-inflammatory, stimulates the formation of new blood vessels, stimulates the cells that produce collagen, stimulates the release of stem cells and increases the bactericidal activity of white blood cells. All these effects favor the process of healing and repair of wounds.

The eschar are very difficult to heal due to the lack of peripheral circulation (in the skin) or peripheral angiopathy that prevents the correct irrigation in the affected area and necessary for the healing process to be carried out properly. The hyperbaric chamber treatment generates a strong hyperoxia and the greater availability of oxygen in the tissues initiates the process of angiogenesis or formation of new blood vessels that are the beginning of the healing process.


Dr. Arturo Prado, Dr. Patricio Andrades and Dr. Susana Benítez, Ulcers due to pressure, recovered from, 2005.

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