Liquid ventilation in cryonics
After legal pronouncement of death, cryonics patients benefit from rapid stabilization to protect the brain from injury. The most fundamental intervention is induction of hypothermia. Unlike other interventions such as cardiopulmonary support (CPS) and administration of neuroprotective medications, induction of hypothermia is an intrinsic part of cryonics. Unfortunately, surface cooling with ice is not a very effective way to rapidly drop the core temperature of the patient. There are a number of alternative cooling methods such as peritoneal, colonic, and gastric lavage but these cooling methods can be logistically challenging and require specific (surgical) skills. As a consequence, application of these cooling methods in cryonics is rare. To date, rapid cooling in cryonics is achieved during blood washout, which requires surgical access to the circulatory system of the patient.
Because the neuroprotective effects of hypothermia on the brain are so profound it would be very desirable to be able to induce rapid cooling without the need for surgery and extracorporeal perfusion. In the mid-1990s, cryonics researcher Mike Darwin realized that one might be able to reap some of the benefits of cardiopulmonary bypass-induced cooling by using cold cyclic lung lavage with an inert liquid. Because all of the patient’s blood travels through the lungs, the lungs can be utilized as an endogenous heat exchanger to cool the patient. With his colleagues at 21st Century Medicine and Critical Care Research (CCR), a number of prototypes were built to deliver and remove chilled perfluorocarbons. Initial canine experiments using this technology were successful and in 2001 a paper was published that documented that cooling rates of 0.5 degrees C/min could be achieved. A number of different terms for this technology have been used including liquid ventilation, mixed-mode liquid ventilation (MMLV), and cold cyclic lung lavage, depending on which aspect of the technology needs emphasis, breathing or cooling.
A basic version of cold cyclic lung lavage with perfluorocarbons was used on Alcor patient A-1876 in 2002. This case constitutes the first documented case of cold cyclic lung lavage in cryonics. Although the case summary states that “the combination of external cooling in the ice bath and fluorocarbon cooling via the lungs had reduced her core temperature from around 36 degrees Celsius at the time of death to approximately 9 degrees in just two-and-a-half hours,” no specific details on the equipment or procedure are given. The report does indicate that rapid indication of hypothermia by delivering and removing cold perfluorocarbons from the lungs is technically feasible in cryonics patients. In 2007, the cryonics company Suspended Animation and CCR reported on the development and fabrication of advanced automated prototypes to induce liquid ventilation that can achieve cooling rates superior to the prior art. The recent prototypes are scaled for human lung volumes and could be used in a cryonics case if people are appropriately trained. Although the concept of liquid breathing is not new, the application of such technologies to induce rapid hypothermia to protect the brain is another example of how cryonics research can contribute to mainstream (emergency) medicine.