OK, I'm working with someone who designed (and patented, so don't get any ideas...) a backboard that has a ridge down the middle to support the spine of a grossly obese person (300+lbs) while doing chest compressions (CPR). The idea is that the compressions done on these people are inneficient or innefective due to the large fat pads on either side of the spine. Because the fat doesn't accumulate as thick directly over the spine, supporting directly under it should bypass the springy effect of the fat pads and allow for full compression.
Now the problem, proving it. I have a $3K Laerdal CPR dummy at my disposal, I can do anything to it that I want, and I want to make it respond like a obese person. On a flat backboard, it should not compress easily or even fully, and when used on the special backboard, it should. Now think of the dummy as nothing but a rectangular box in the shape of a torso, with a pressure sensor in the middle. I say box because the back is a solid, stiff, rectangle...
My idea is that, like the compression sensor in the dummy, I can use springs to simulate the fat on either side of the dummy along the axillary lines (from the armpits straight down). My logic behind using springs rather than ballistics gelatin is that they can be calibrated to replicate a specific force (spring force = F = -kx) for a low price. To use ballistics gelatin would require a walk in cooler, an obese man (I have one of these), lots of plaster to mold his back, lots of free time, time to play with the formula because ballistics gelatin is formulated to replicate muscle not fat, and last but not least, lots of money... (it's $350 for a 50Lb tub of the gelatin)
So with a row of springs down either side of the dummy, with it lying on a flat backboard, performing chest compressions would first compress the springs(fat pads), and then compress the chest sensor when the springs I added are fully compressed.
On the backboard with the ridge, the dummy would be supported along the midline and therefore all compression force would be directed directly to the chest compression sensor.
Now the problem. How do I determine the correct spring strength to use with the dummy??? I have absolutely no clue how to measure the force required to squish an obese person's fat...
BTW, I'm a medical student, I'm not tied to this project financially in any way and will not benefit from the approval of it for medical trials, so don't ask me for money if we figure this out, I'm not going to get any
