The researchers applied a 40 N force, about 4 kg, orthogonal to the back of the model head. This simulates the tissue loading weight for an average adult head. in a prone position. Therefore, the forehead and chin bear the weight of the forehead on the donut-shaped surface. 

Material interface conditions

The researchers measured the interface pressures between the skin and the surface for multiple patients. These measurements were done without applying the dressing. The pressure was applied for one minute and data regarding the peak and average pressure was collected.

Validation of facial pressure measurements

The researchers calculated the distributions of the stresses and strain in the skin and the subcutaneous fat tissues. They later calculated the volumetric exposure of the skin and fat layer (forehead and chin) to the stress and strain. Finally, the team calculated the percent reduction in the area under the tissue exposure curves for the treatment and control groups for both areas (forehead and chin).

Data analysis methods for prophylactic dressings

The SED function demonstrates the strain energy of an object against a deformation gradient. In the study, the researches used this to see the strain in the area of the skin with the applied pressure. 

Strain energy density function

The researchers developed two anatomically accurate models of the human head. A model would serve as a control, while the other is placed in a prone position with the dressing between the skin and the resting surface. These models would provide quantitative information about facial skin and subcutaneous fat loading while in a prone position.


Ohio State University, Columbus

The weight of the head is held up by the head; however COVID-19 patients placed in a prone position may experience pressure ulcers resulting from prolonged exposure/contact of the surface with the skin. Prophylactic dressing is a multi-layered silicone foam dressing which can be applied to the resting surface to relieve the stress and strain of the body weight on the soft tissue. This reduces the chances of a pressure ulcer especially for COVID-19 patients with low mobility. 

Prophylactic Dressings

Peko, L, Barakat‐Johnson, M, Gefen, A. Protecting prone positioned patients from facial pressure ulcers using prophylactic dressings: A timely biomechanical analysis in the context of the COVID‐19 pandemic. Int Wound J. 2020; 1– 12. 
https://doi.org/10.1111/iwj.13435

Using prophylactic dressing to prevent facial pressure ulcers for COVID-19 patients

A pressure ulcer is damage to the soft tissue resulting from prolonged exposure of the skin to the resting surface. These often occur due to the patient's bodyweight forces which results in greater stress and strain to the area of the skin exposed to the surface. Patients with low mobility, or those placed in a prone position are at greater risk of a pressure ulcer. 

Pressure Ulcers

Methodology for testing effectiveness of prophylactic dressing

- Stress and strain distributions on facial skin
- Stress and strain distribution in subcutaneous fat layer

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