Ice Bath
An ice bath is used to contain the patient and the ice during initial cool down to zero C. It must be able to safely move the heavy unstable load and must be easy to load into the transport vehicle. An ice bath is an absolute necessity, and is probably the most important piece of equipment in cryonics. Each cryonics organization designs and builds their own ice baths to match their own unique needs.
Examples
Here are some examples of ice baths which have been designed by other cryonics organizations:
Old Alcor PIB (plywood base, PVC pipe frame)
Alcor Ice Bath
Alcor Mobile Advanced Rescue Cart (welded steel frame)
Suspended Animation Equipment (3 different types shown. Welded and hinged stainless steel frames)
Cryonics Institute Thumper and PIB. Being used on a dog. (metal framework appears to be assembled rather than welded.)
Design considerations
Our ice bath is made from square aluminum tubing which has a high strength to weight ratio compared to most other materials.
It rides low to the ground for stability. It was designed to allow easy mounting and positioning of our model 1007 Thumper. 1" aluminum tubing with 1/16" walls is used throughout. Anodized aluminum would give a cleaner look but would also cost more. The external dimensions are 73" long, 22" wide, and 11" deep, excluding the wheels and Thumper. Internal dimensions are 71" long, 20" wide, and 10" deep.
The joints use these connectors from eztube.com:
The connectors have welded steel cores with ABS/nylon jackets. They come in a wide variety of orthogonal configurations. The entire ice bath frame was simply hammered together and is amazingly strong. On the side where the Thumper is mounted, the connectors had to be cut with a large grinding wheel because they were too long for such short lengths of tubing. This could be avoided in the future by only using one horizontal tube in that area. The tubes themselves were cut with a circular miter saw using a plywood blade. Some aluminum debris needed to be removed from the teeth after a dozen or so cuts. The plywood base is only 3/8" for lightness, and there are no horizontal supports under it. There are a number of things that could be done to improve support under the plywood, including a second box structure for the wheel assembly, or even a simple tube bolted under the plywood. Where the plywood is bolted to the aluminum frame, fender washers are used. The liner was made with reinforced 18 oz. vinyl of the kind commonly used to make tarps and covers for big trucks. It is a single piece, origami folded at the corners to avoid seams under the water level. The tent and awning company built the liner for $100 total for all material and labor. They also applied all the snaps, using screws with snap heads that easily screwed into the tubing.
Quick load calculation: For the calculation, we will assume that the icebath will be filled with a patient and water to a depth of 7" (it would be less in reality), the total volume of water would be 7*71*20=9940 in3 or 5.75 ft3. At 62 lb/ft3, the total weight would be 356 lbs. The mechanical stress of the Thumper need not be included because that is handled by the backboard. Subjectively, the plywood seems strong enough to support this weight. It can support a 150 lb person gently bouncing on one concentrated point in the middle. A better test would be to fill it with water.
There will be lifting straps or webbing that goes in under the patient in order to allow lifting out of the ice bath later.
Future design considerations
Because this is our first ice bath, extra features are minimal. It was designed specifically for speed and simplicity of assembly. But there are many planned improvements for future ice baths. In the end, we will have a variety of ice baths for different purposes. Here are some of the planned improvements. The improvements are NOT all for a single ice bath:
Head ice bath: Sits inside the main ice bath and allows concentrated cooling of the head without large amounts of ice.
Water circulation: Keeps the water moving on all body surfaces to improve cooling. Uses battery operated pump.
Drain: This is commonly done by incorporating a valve and extra hose into the water circulation system. The pump can then be used to pump extra water into a nearby container or sink.
Insulation: A double walled liner with wool batting or foam rubber between the layers can help prevent the ice from melting so quickly. It also helps reduce condensation on the exterior of the liner. A camping mat can be used under the patient.
IV pole: If the patient already has an IV, it is best to leave it in place in order to deliver medications postmortem. A pole then becomes necessary.
Foldable for air transport: Very compact and lightweight. Fast to assemble on site. Base could be polyproplylene or metal mesh.
Cart: Strong and sturdy. Ice bath rides high, more like a standard gurney. Extensive equipment built into cart under the ice bath. Requires a truck with a lift and plenty of headroom.
Reconfigurable: Legs that fold or can be removed. Wheels that quickly attach directly to bath for low riding configuration.
Different sizes: Extra wide and sturdy designs. Or extra long designs.
Maneuverability: To allow going around tight corners and fitting in small elevators. Ends could be tapered. Foot end could fold upwards.
Hoists: The baths can be very heavy. Cranes, winches, hoists, lifts, etc all make handling the weight easier and safer, especially if few people are available.
Active compression decompression: Specially built Thumper is mounted over the patient and attached to the side rails. It pushes on the chest and also pulls on the upstroke using a suction cup. This increases the efficiency of the cardiopulmonary support. Expensive.
Frame hardware: This website: www.8020.net looks like a very good alternative framing solution. One advantage is that it can be disassembled. One disadvantage is that it would be hard to disinfect the deep grooves. Because of its very infrequent use, this is an acceptable disadvantage.
Design limitations
Over the years, a wide variety of ideas have been tried. Some of them just didn't work very well for one reason or another. Some of the ideas listed here are actually currently in use. But the disadvantages must be carefully considered before using.
Plastic pipe: Base made of plywood. Frame for liner made of 2" PVC pipe. The problem is that the ice bath cannot be lifted by the pipe framework because it is not strong enough, especially when cold. This design is still sometimes used due to low cost.
Spray heads: They cause splashing which is a biohazard. Any water circulation device must be properly diffused.
Solid walls: Nobody has ever built an ice bath with solid walls. Plywood might be too heavy. Fiberglass, plastic, or sheetmetal might work. But it would be difficult to ensure that a large solid design with seams would be watertight. With a solid design, it would become very difficult to mount a standard Thumper. A special slot would have to be built. And most importantly, the additional weight would make lifting more difficult and dangerous.
Ramp: To roll a heavy ice bath into a vehicle. This can be a low cost option compared to a lift. But the steeper, the longer, and the narrower the ramp, the more impractical it becomes. It has been taken to extremes, where an electric winch was needed to pull the cart up the ramp, and a leveling jack was needed to prop up one end of the cart. It can become a complicated and dangerous technique. It is also difficult to park such a vehicle leaving enough room for the very long ramp that comes out the side door.
Plastic base plate: The wrong kind of plastic can become brittle and break when cold.
Ambulance cot: The wheelbase is too small and it becomes tipsy. Also, older small wheels do not handle irregularities like door thresholds. One small shift can cause the water filled bath to suddenly lurch dangerously.
Autopulse: The Autopulse is a mechanical CPS device which lies under the patient. It uses batteries to power a motor that pulls on a strap extended around the patient. Due to the ice bath, this is an unworkable idea for cryonics. Attempts to adapt it to work with an ice bath have resulted in water damage to the device. Even the condensation that is always present when using an ice bath can render the device useless.