Effect of Alternating Pressure Overlay on Weight Bearing Tissue Tolerance in People With Spinal Cord Injury

Tissue ischemia is one of the main etiologies of pressure injury. It is inevitable during bed-ridden and wheelchair bound conditions, such as spinal cord injury (SCI), or prolonged surgery procedure in the operating room. Active alternating pressure (AP) mattresses are covered by Medicare policy for patients with multiple/large stage 2/ stage 3 pressure injuries to relief interface pressure and prevent recurrence of pressure injuries. Previous studies demonstrated that the protective mechanisms of AP on pressure injury include redistribution of surface pressure, and allowing more blood supplies while lying on the support surface. The Dabir AP overlay is low profile yet possesses similar characteristics as other AP mattresses on the market; it is intended for clinical use, such as operation room (OR) where AP mattresses may not be an option. We expect Dabir AP overlay will be beneficial to people at risk of pressure injury by maintaining the blood supply during weight bearing condition.

The objective of this study is to evaluate the protective mechanisms of Dabir AP overlay on weight bearing tissue of people with chronic spinal cord injury (SCI). Our central hypothesis is that the Dabir AP overlay will cause lower amount of interface pressure and allow more skin blood flow during weight bearing as compared to regular OR overlay.

Each subject will undergo two study protocols: AP and control, and the order of the protocols will be randomized by drawing one envelope from the envelope pool. We will start with a pool of total 20 envelopes (10 envelopes indicating AP protocol first, and 10 envelopes indicating control protocol first). A 30-minute washout period will be provided in between the two protocols. Two Laser Doppler flowmetry (LDF) flat probes (moor instrument, Wilmington, DE) will be taped to the sacrum and one heel to collect the skin blood flow response throughout both AP and control protocols. A whole body pressure mapping system will be used between the subject and the overlay to collect the inter pressure data. For the AP cycle, we will use four 10-minute cycles (5 minutes of high pressure and 5 minutes of low pressure).

AP protocol: The subject will first lie on his/her side quietly for 10 minutes to collect the baseline skin blood flow, followed by lying supine on the Dabir AP overlay for 40 minutes, and then side lying for 30 minutes to collect the first reactive hyperemic response. To test the effect of preconditioning, the subject will then lie supine on the OR overlay for 40 minutes followed by side lying for 30 minutes for the second reactive hyperemic response.

Control protocol: The subject will first lie on his/her side quietly for 10 minutes to collect the baseline skin blood flow, followed by lying supine on the OR overlay for 40 minutes, and then side lying for 30 minutes to collect the reactive hyperemic response for control protocol.