Use of a Shear Reduction Surface in Pre-hospital Transport

This study enrolled healthy adult volunteers of any race or gender, stratified into 3 Body Mass Index (BMI) categories (≤20, 20.1-24.9, ≥25), who served as their own controls. The setting for this study was on a closed driving course utilized for training of emergency and law enforcement personnel, and the vehicle used was a standard ground ambulance affiliated with the Medical Transport of a tertiary medical center.

Apparatus and/or instruments: A commercial full-length LiquiCell® anti-shear mattress overlay (ASMO) (Birchwood Laboratories, Eden Prairie MN) was placed on the standard ambulance stretcher mattress. Shear force and tissue interface pressure was measured during a full stop, acceleration, travelling at 30 mph, deceleration, and a full stop by a PREDIA device (Molten Corporation, Hiroshima Japan) through reusable sensors attached to the sacrum, ischial tuberosity, and heel.

Procedures: Following written informed consent, subjects were weighed and measured with a calibrated scale to calculate a current BMI. Three PREDIA sensors were secured to three sites (sacrum, ischial tuberosity, and heel) with double-stick tape. Subjects wore standard hospital scrub bottoms, and were secured supine to the ambulance stretcher using standard procedure. Subjects were blinded to the presence of the LiquiCell® ASMO overlay by a sheet covering on the stretcher. The ASMO was placed according to a simple randomization table. The stretcher was initially be placed with 0 degree head-of-bed (HOB) elevation, followed by subsequent HOB elevations of 15 degrees and 30 degrees. HOB elevations were verified using a standard goniometer. The ambulance traveled over a closed course driven by ambulance staff members that had passed the mandatory Coaching the Emergency Vehicle Operator (CEVO) driving course. The course included at maximum speed of 30 mph and 5 complete stops at each of 3 HOB elevations (0, 15, and 30 degrees). Shear measurements (measured in Newtons) and pressure measurements (measured in mmHg) for each anatomical site were taken with the PREDIA sensors during a full stop, acceleration, travelling at 30 mph, deceleration, and a full stop for each "run". At the beginning and completion of each set of 5 runs, subjects were asked to rate their discomfort on a scale of 0 (no discomfort) to 10 (worst discomfort imaginable). Following the first set of 15 runs, the course was repeated with or without the LiquiCell® ASMO according to the randomization table.