Vacuum mattress

A vacuum mattress, or vacmat, is a medical device used for the immobilisation of patients, especially in case of a vertebra, pelvis or limb trauma (especially for femur trauma). It is also used for manual transportation of patients for short distances (it replaces the stretcher). It was invented by Loed and Haederlé, who called it "shell" mattress (matelas coquille in French).

A vacuum mattress consists of a sealed air-tight (typically polymer) bag enclosing small beads (typically polystyrene balls) and fitted with one or more valves. While at ambient air pressure, the beads free to move, but when the mattress has been moulded and the air evacuated, external atmospheric pressure locks the beads in place (jamming) and the mattress becomes rigid.

When used medically this principle allows a patient is put on the mattress (e.g. with a scoop stretcher), the sides of the mattress arranged around the patient and when the air inside is evacuated the mattress forms a conformal cradle allowing an injury to be stabilised, straps fastened, and the patient protected sufficiently well that they can be transported.

For this reason the bag is typically bigger than an adult human body (though the same principle may be employed to create an 'instant' cast to stabilise an injured limb. In use a sheet is usually put on the vacuum mattress to:

The full spine immobilisation (splint) is performed with:

The vacuum mattress is put on a stretcher or possibly on a long spine board. The straps are put under the mattress, along its side, so they do not reach the ground. Then, the polystyrene balls are distributed evenly through the mattress by shaking its surface. (A section with fewer balls would be less rigid, conversely if balls are concentrated at any given point this becomes more rigid.) A sheet is put on the mattress, folded so it will be possible to pull it to wrap the casualty into using an S-fold and finally a team member should double-check the pump (manual or electrical) is set to either pump air out of the bag.

...
Wikipedia