Backrest Elevation Shows No Effect on Sacral Tissue Integrity

Body positioning in critically ill patients receiving mechanical ventilation may not be as important or as effective as once thought, claims a new study.

Researchers at Virginia Commonwealth University (Richmond, USA), the University of Miami (FL, USA), and Virginia Commonwealth University Medical Center (VCU; Richmond, USA) conducted a study involving 84 critically ill adult patients expected to undergo intubation and mechanical ventilation for at least 24 hours so as to examine the effect of backrest elevation on the integrity of sacral tissue. Backrest elevation was continuously measured with mechanical accelerometers, with sacral tissue and integrity evaluated with high-frequency sonography.

The results showed that level of backrest elevation was not associated with changes in tissue integrity. Linear models indicated no significant difference among the proportions of time spent at less than 20°, 20° to 30°, or greater than 30° among participants with no injury, no change in injury, improvement in injury, or injury that worsened. Of these, most participants had no injury, or an injury with no change; only a few participants had an injury that was improving or worsening. The study was published on March 1, 2018, in the American Journal of Critical Care.

“Although use of lower backrest elevation is recommended for prevention of pressure injuries, for critically ill patients receiving mechanical ventilation, higher backrest positions are recommended to reduce the risk of ventilator-associated pneumonia,” concluded lead author Mary Jo Grap, RN, PhD, of VCU, and colleagues. “Because pressure is a primary mechanism in the formation of injury, higher backrest elevations may have deleterious effects on tissue integrity, leading to shear and pressure injury, especially affecting the integrity of tissue in the sacral area.”

The sacrum is a large wedge shaped vertebra at the inferior end of the spine; it forms the solid base of the spinal column, supporting the weight of the upper body as it is spread across the pelvis and into the legs. Pressure ulcers, which form as a direct result of pressure over a bony prominence, occur all around the pelvic girdle, most often at the ischium, greater trochanter, and the sacrum. Specific risk factors for sacral pressure ulcers include lying in the supine position and fecal incontinence.

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