Cost-effective therapeutic hypothermia treatment device for hypoxic ischemic encephalopathy

Abstract

Despite recent advances in neonatal care and monitoring, asphyxia globally accounts for 23% of the 4 million annual deaths of newborns, and leads to hypoxic-ischemic encephalopathy (HIE). Occurring in five of 1000 live-born infants globally and even more in developing countries, HIE is a serious problem that causes death in 25%-50% of affected neonates and neurological disability to at least 25% of survivors. In order to prevent the damage caused by HIE, our invention provides an effective whole-body cooling of the neonates by utilizing evaporation and an endothermic reaction. Our device is composed of basic electronics, clay pots, sand, and urea-based instant cold pack powder. A larger clay pot, lined with nearly 5 cm of sand, contains a smaller pot, where the neonate will be placed for therapeutic treatment. When the sand is mixed with instant cold pack urea powder and wetted with water, the device can extract heat from inside to outside and maintain the inner pot at 17°C for more than 24 hours with monitoring by LED lights and thermistors. Using a piglet model, we confirmed that our device fits the specific parameters of therapeutic hypothermia, lowering the body temperature to 33.5°C with a 1°C margin of error. After the therapeutic hypothermia treatment, warming is regulated by adjusting the amount of water added and the location of baby inside the device. Our invention uniquely limits the amount of electricity required to power and operate the device compared with current expensive and high-tech devices available in the United States. Our device costs a maximum of 40 dollars and is simple enough to be used in neonatal intensive care units in developing countries.

Keywords: birth asphyxia; evaporative cooling; hypoxic ischemic encephalopathy; neuroprotection; therapeutic hypothermia.

Figure 1

Computer-aided design of the therapeutic hypothermia device.

Figure 2

Schematic of cooling. Note: Temperature changes based on heat transfer, water diffusion, and air flow of the surrounding system.

Figure 3

Model of energy flow of device. Notes: The energy usage is transferred to either the cooling or warming method through a transfer function. The cooling or warming method transfers to a change in skin and rectal temperature. All of the manipulations are controlled via the control system of the device.

Figure 4

Digital output of the control system. Notes: The skin and rectal thermometers are placed in series. Recordings from these probes result in changes in the respective LED light.

Figure 5

Verification of inner pot temperature. Utilizing modeling techniques, a temperature of 17°C was established as being capable of cooling the neonate to 33.5°C within one hour and 20 minutes (A and B). This was verified (C and D) via testing.

Figure 6

Piglet model results. (A) Demonstrates the rapid cooling of the piglet within the modeling parameters. However, because there was overshoot, passive warming was required during the cooling process. (B) Demonstrates sustained temperature for over 3 hours. (C) Demonstrates effective warming rate of 0.5°C per hour.