Designing a new Personal Protective Equipment (PPE) for extended use by caretakers by reducing heat and moisture.
Heat build-up in PPE suits is a major problem. The human body produces up to 600 watts of heat in intense activities and it also has the capacity to produce more than 1.5 liters of sweat within an hour of constant physical exercises.
In the West African countries that have been struck by Ebola, it is fundamental to understand infrastructure needed (electric grid, temperature control, roads, housing) for the PPE ecosystem to work. An exercise of tactical deployment must consider existing in-country capabilities and infrastructure as well as an orchestration with care giver and support networks between non-governmental organizations, non-profits, local government and foreign government agents on the field and on the ground.
My parents were practicing doctors during the 2002/2003 outbreaks of SARS in Singapore. As a non-medical trained person, I could only watch as my family and all my family friends were suddenly dealing with SARS. In Singapore, the issues of the PPE suits were already prevalent to me, but I simply lacked the knowledge, skills and ability to tackle it. In some sense, doing this, is the same to me as me protecting my family and my family’s friends.
In current PPE suits, it is extremely difficult for the heat and sweat generated by the Human body to efficiently dissipate. Rapid exhaustion and discomfort reduce the total time a care giver provides from hours –in a controlled room environment- to under 60 minutes in ambient temperatures for the profile of the West African nations stricken by Ebola.
Caretakers are the highest risk of infection when they are taking off their PPE, by extending the operating time in which they can operate in their PPE, it would reduce the number of times the caretaker exposes themselves to the risk of infection.
The situation in Ebola-stricken West African countries has exacerbated local governments and has augmented a challenging problem of logistics to deliver emergency response right now. During our past weeks of research, several conversations with both AID workers and residents of the affected areas have given us a better picture of the resources on the ground and enabled us to envisage a technology and in-country capability for our proposed solution.
The Weather profile of West Africa has a mixture of high humidity and intense heat. The rainy season brings large amounts of precipitation and cloud cover.
With an expected dry season early in the year and heavy rains from May onwards. This would imply that the majority of the people would be indoors or shade for the majority of the time, and care for infected patients would be in the shade. Thus rendering any onboard power generation through Photovoltaic Solar Panel systems impractical.
Freetown and Monrovia are the rainiest capitals of the year, and experience extreme humidity. With 60% to 100% Humidity throughout the year, cooling process through evaporate cooling, is rendered ineffective, which is most effect at under 50% humidity.
Complete weather breakdown for Monrovia can be analysed here:
547 million people in the African continent lack electricity of any kind. Electrical Infrastructure is rare and intermittent in the region stricken by the Ebola Epidemic. Generators and photovoltaic solar power serve some areas, but are only usable for short periods of time. Expensive diesel-powered electric generators can only operate at a few hours a day and clog often from poor quality of the fuel which is also scarce. Photovoltaic solar power performance drops towards the middle of the year as the rainy season starts. Both of the above mentioned systems do not provide enough power to turn water into ice, and do not provide efficient cooling solutions. Solar Refrigerators are often used to hold medicines, and are not suitable for creating ice either.
However, there is an abundance of charcoal for cooking which may be used as source of energy. Further in this piece, we will describe a process where we will be able to convert the heat of fire into a chilling process.
Clean Water & Sanitation
Clean Water is tanked in, so access to portable water is restricted to the most important uses. The majority of inhabitants in this region are living in slums with no access to clean drinking water and rely on drinking water directly from rivers and lakes.
As such, access to portable water useful for medical purposes is scarce and its use in refined technology is also exceedingly difficult.
Roads and Transport
Seasonal dirt roads are the majority the road network. These connect rural areas and cities and it is prevalent to have delays of days to cross relatively short distances. The supply of deliveries becomes difficult and unpredictable. Once the rainy season comes, most of these roads become inaccessible due to mudslides.
PPE Design Brief
This solution has been designed for users who are primarily engaged in prolonged use of PPE suits in ambient temperatures. The Vest will be layered with a series of heat pipes that are designed to flex with the user to a metal plate that is located at the bottom of the vest that suits just above the waist of the wearer. (US 5386701 A)
By constructing the heat pipes of the vest with an alcohol we can not only improve the heat transfer properties, but also allow us to reduce the weight penalty associated with this type of technology (US 6684940 B1),
The vest would interface magnetically with an external cooling source on the exterior of the PPE. Magnets would allow the suit be physically connected to the cooling process while at the same time, prevent a breach in the integrity of the suit. This gives us nearly incredible flexibility in cooling options.
The external cooling source could be as something as simple as a small heat sink or a battery operated fan on top of a heat sink if the charging is present.
Currently we are developing the technology to produce a “cold battery” from an external heat source such as a flame. We are basing this technology on an absorption fridge technology (US1781541 A) , which can uses an external heat source, such as a coal fire, which is common in this region of West Africa, to drive a process where the interaction of 2 liquids actually reduces the temperature of a targeting object. It is possible to use this method to pre-chill cold packs, as the interface is external of the suit, the cold packs can be swapped out as needed, providing indefinite cooling to the user in the suit.
The absorption fridge technology can be enhanced significantly with 3D printing to print out the complex structures required improve the cooling process while reducing volume.
This gives us a cooling solution that can effectively transfer heat away from the user, which requires no moving parts, does not require support directly or indirectly form electrical Infrastructure, low to no maintenance and requires little to no training to support.
The ability of the suit to remove heat from 100 watts to 600 watts of heat will considerable increase the length of time a person can be in the suit.
On 31st OCtober, the WHO issued guidelines on personal protective equipment for maximum protection possible against the Ebola virus. Now that the standard has being defined, it is now possible to begin proper design of a suit that will not only meet protection requirements, but also conform to a standard.
There are no real standard specifications for Ebola. The closest thing to a standard is from MSF (tychem suits, custom made hood with integrated mask, goggles, etc) The new WHO specifications outline on the level of protection required for various types of care giver activities. An example is the compulsory recommendation of double gloving.
It is important to understand scale.
As a reference, a water molecule is 0.3nm or 3 angstroms in size. The Ebola virus’ filament is about 970 nm in length and about 80nm in diameter. For comparison, the world’s smallest virus, Porcine circovirus, is about 17nm in diameter.
Filtration technology has already allowed us to remove these viruses from our water supply. We have done this for more than a decade already, the technology to
Looking at the expired patents around Gortex, (US3953566 A, US4187390 A, US4194041 A)
it uses a layer of Teflon to act as a hydrophobic layer as a water repellent. It is also able to allow water vapor to pass through. It also allows water vapor to pass through. It would be possible to improve the goretex fabric to not only restrict the Ebola virus from penetrating the integrity of the suit, but to still allow water vapor to escape.
It is possible to find materials that would have pore sizes less than 80 nm…thus keeping out the Ebola Virus from infecting the individual while allows water vapor to still escape.
If this works, then we will be able to take advantage of the human’s body to do evaporation cooling.
Initial Designs have being seen by Material engineers and other various other engineers and they have determined that the design is sound and is worth more investigation. My previous research work was in the development of medical sensor networks for personal health monitoring.
In Conclusion, creating a new generation PPE is a multifaceted problem, which requires significant understanding of the in-country capabilities, infrastructure as well as local culture, faith & belief system’s rituals, human behavior, variation in body types, comfort, usability, durability, reusability and safety. We believe that it is possible to create a non-electrical suit that will ensure the safety of the people while improving their comfort and survivability.