Progress Toward Intermediate Temperature Storage

In the previous Alcor News we reported that Alcor has acquired the prototype of an Intermediate Temperature Storage (ITS) device developed by Brian Wowk of 21st Century Medicine. (For an explanation of why ITS is desirable, please check the explanatory section in Alcor News #13 dated July 1st, 2003.)

Our new lab assistant, Todd Huffman, has been studying Brian Wowk’s design and has visited 21st Century Medicine to discuss reliability issues and possible modifications. Since the ITS pod will be cooled by positioning it above a pool of liquid nitrogen inside a Dewar, we have been debating which type of Dewar to use. An off-the-shelf industrial design is available, large enough to contain seven ITS pods (one in the center and six around it, in a hexagonal pattern). However, our proprietary “bigfoot” Dewar design is much taller, only slightly more expensive, and we have had extensive experience operating them over the past decade. A “bigfoot” seems our best option at this point.

In theory, it would be tall enough to contain a stack of three layers of ITS pods, with seven pods in each layer. The problem is that a tall Dewar will allow a more severe temperature gradient. In other words, the pods at the top will tend to be warmer than the pods at the bottom, and ITS requires that the temperature should be controlled with some precision.

One way around the problem is to use an internal framework of metal such as aluminum, which is a good conductor of heat and could minimize the temperature gradient. Another possibility is to fill the lower part of the Dewar with conventional neuropatients fully immersed in liquid nitrogen, with a single layer of ITS pods above them at the top. The disadvantage of this configuration is that we would have to modify our standard neuropatient containment shell. Also the ITS pods would get in the way during insertion or removal of neuropatients.

Another issue which Todd is investigating is the optimal refill system to maintain the reservoir of liquid nitrogen. A gravity feed would provide the security of constant refill without pumps, but would be grossly inefficient since the pipe connecting it with the Dewar cannot be optimally insulated and will promote nitrogen boiloff.

Using a pump for automatic refill sounds intuitively risky, but low-temperature pump design has been perfected in industrial applications, and a Dewar refill pump probably would run only for a few minutes per week. Two pumps could be installed in parallel for redundancy.

Todd has been tabulating every conceivable failure mode, including liquid-nitrogen level sensor malfunction (Dewar will boil dry), failure of temperature sensor inside ITS pod (patient may become too cold or too warm), wire-break failure, pod heater failure, control system failure, and many others.

Probably we will need four months to explore all these failure modes and develop satisfactory solutions, after which the construction and testing of actual patient storage units may take another two months. This is longer than we would like, but obviously the system must be absolutely reliable before we can offer it as an option to our members.

We can’t predict how much ITS will cost relative to conventional Dewar storage until we have established all the components in the system and have measured the liquid nitrogen boiloff rate.

Intermediate Temperature Storage: A New Era at Alcor

Maintaining patients at an intermediate temperature means keeping them warmer than liquid nitrogen, but cold enough to inhibit biological decay. For years we have wanted to provide this option. On June 14th, we came much closer to our goal.

Why Intermediate Temperature Storage is Necessary

If cryoprotective perfusion is performed successfully with a high terminal concentration, residual amounts of water in solution in the brain tend to solidify instead of forming ice crystals. When we use the vitrification solution which is now standard for all Alcor neuropatients, the entire brain should become a glassy solid as its temperature drops below the “glass transition point” around -125 degrees Celsius.

Traditionally, we have maintained our cryopatients at -196 degrees, the temperature of liquid nitrogen. We use liquid nitrogen because it is cheap, nontoxic, convenient, and requires no refrigeration equipment at our facility. The liquid is “precooled” when it is delivered. Unfortunately, it is colder than we would really like it to be.

When a cryopatient makes the long journey from -125 to -196 degrees, some portions of the brain inevitably tend to cool faster than others. This creates thermal stress which can result in fracturing. We use a “crackphone” to sense and record vibrations which we believe are an accurate indication of fracturing events.

Proponents of nanotechnology believe that fracturing will be relatively easy to repair in the future compared with cellular damage, but still we would like to prevent it. The problem probably can be minimized or even eliminated if the patient isn’t allowed to get so cold, and is held at a temperature just below the glass transition point. In other words, we would like our patients to be cold enough to vitrify, but not so cold that they start to fracture. Unfortunately the only easy way to achieve this has been by using an expensive laboratory freezer–until now.

A New Way to Maintain an Intermediate Temperature

On June 14th, in Rancho Cucamonga, California, biophysicist Brian Wowk of 21st Century Medicine gave a remarkable presentation attended by all Alcor board members and many staff members. Dr. Wowk has developed a simple, reliable design for an intermediate temperature storage device using a heavy-gauge metal container enclosed in a jacket of closed-cell insulating foam fitted with two 2-watt heaters. The insulating jacket is then immersed in liquid nitrogen, and the heaters are run variably by an external controller to maintain the desired temperature inside the metal liner, which conducts heat and minimizes the thermal gradient.

According to Dr. Wowk, seven of his storage devices will fit beside each other within the diameter of a typical “bigfoot” dewar of the design that Alcor uses. The initial cost of building each storage device will be around $2,000, but a greater expense will be incurred in the long term as the heating elements will increase the total boiloff of liquid nitrogen in the enclosing Dewar. Also, because of the foam insulating jacket, each intermediate temperature storage device will occupy a greater volume compared with a standard neuro container. However, we believe that many of our members may feel that a higher payment for longterm care is a very reasonable tradeoff if Dr. Wowk’s design minimizes or eliminates fracturing.

Alcor has purchased Dr. Wowk’s first prototype and will be testing it for reliability and boiloff. After we have the numbers, we will be able to offer intermediate temperature storage probably as an extra-cost option. We can’t estimate the precise cost at this time, but Alcor News will provide additional updates in the future.

This is the most exciting development in cryonics since the advent of vitrification, and we’re especially pleased by its simplicity. We believe there is an excellent chance that this will become the preferred method of patient care at Alcor.