ArdenMed

Our Resilient Oxygen Concentrator

Low and middle income countries are in dire need of resilient oxygen concentrators that are fit-for-purpose for low and middle income countries. ArdenMed’s more than 50 Volunteers have been working tirelessly since April 2021 to develop innovative solutions to address the problems faced in low-resource settings.

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The Problem with Oxygen Concentrators

Temperature

High temperatures reduce the efficiency of the nitrogen filtering process. This results in lower oxygen purity unless accounted for by the machine.

Humidity

Water from the intake air is absorbed inside the concentrator and gradually decreases its ability to produce oxygen.

Power Issues

Concentrators rely on continuous power and patients can't breathe during outages. Power fluctuations often break devices.

Price

Clinics and health centers simply can't afford new oxygen concentrators. Especially not if they need frequent replacement.

Dust & Dirt

Filters must be cleaned frequently or else they increase power consumption and can damage the device.

Altitude

Oxygen and pressure are lower in high altitude environments, which leads to insufficient oxygen purity unless accounted for by the machine.

Servicing

40% - 70% of medical devices in low resource settings are not operational due to a lack of trained servicing staff and spare parts.1https://gh.bmj.com/content/4/5/e001785

How do Oxygen Concentrators work?

There are several methods to concentrate oxygen. Large facilities for example cool down regular air to extreme temperatures until they become liquid. Then, like a distillery of alcohol, oxygen can be extracted from the liquid air. However, these oxygen plants are only feasible at huge scales and require constant technical monitoring and servicing. Most portable oxygen concentrators use a technique called pressure swing adsorption (PSA). 

 

In this process, air flows is pumped into a cylinder filled with granulites of Zeolite (or a similar material) which has electrostatic surface properties that attract nitrogen more than oxygen. With the right pressure, temperature and duration of the adsorption, oxygen with a puriy of more than 90% will come out of the other side of the cylinder. Once the Zeolite has reached it’s adsorption capacity, the cylinders must be emptied and given some time to release as much of the nitrogen as possible before starting another cycle.Therefore, to produce oxygen continuously usually two cylinders are pressurized alternatingly which is where the term pressure swing comes from. 

Our Solutions

Unlike most other Oxygen Concentrator Manufacturers who usually copy existing designs with minor improvements, we have started at the basic physical principles that govern the adsorption process and have choosen our design and parameters such that they adress above problems in the most ideal way. Here is how we have addressed each of them.

Power Issues
Two major electrical problems govern our machine design.

First, power grids in our target countries are often fluctuating. The device must be able to handle lower frequencies of the grid when they are under heavy load and handle power surges when the grid comes back online after an outage. To address this issue, we use a high quality power supply unit which transforms the alternating current to direct current, which is then used to power a three-phase motor drive controller that controls our pump. This way, the power supply, handles voltage sags, dropouts and overvoltage events while the motor controller works to limit inrush current that could damage the compressor, which is the key component of the concentrator.

Second, power can be out for several hours at a time or be unavailable altogether. To address this issue, we have taken steps to improve the efficiency of the device such that it becomes feasible to bridge the median power outage duration seamlessly using a built-in battery. There are a number of steps to take to increase power efficiency compared to existing designs. Simply using larger zeolite tanks allows us to reduce the pressure required, which is the main driver of inefficiencies in the system. At the core of our pressure solution is a custom-made pump which we are currently developing. It is based on the scroll pump principle, which is known for its exceptional reliability, low noise and power efficiency. Additionally, it can be run backwards (unlike the compressors used in traditional concentrator designs) which allows us to use the compressor as a generator during the pressure release stage and use it to recharge the internal battery, which improves the power efficiency during battery operation. This also enables us to create a slight vacuum during the material recovery stage which improves the absorption process and longevity of the material and further lets us decrease pressure, which lowers energy consumption as well.

Finally, we implemented a solar power converter as well as a 12V input such that the device can be powered with maximum efficiency directly from a solar panel or run from a car cigarette lighter
Humidity
Since zeolite is a porous material, it tends to absorb humidity from ambient air, but unlike nitrogen, the water is not released easily during depressurization. Over the years, or in very humid environments, even in a few weeks, the zeolite will lose its capacity to adsorb nitrogen until the device can no longer produce oxygen.

Here we utilize the inherent cooling capacity of any pressurization process. When gas is pressurized, its temperature increases. For an efficient adsorption process, the air needs to be cooled down, which happens through a heat exchanger with the exhaust nitrogen. Since energy has been removed from the air during the cooling process, the released nitrogen will cool down significantly upon depressurization. We utilize this inherent cooling capacity of the concentrator to cool down the incoming, moist air until the water condenses and falls out. The remaining air is then passed through a cost-effective moisture absorbing material to remove the remaining water. The absorbing material is then dried by the later warm exhaust nitrogen, thus closing the cycle without consuming any additional electricity and only a few, standard, cost-effective parts.
Temperature
As the temperature of the ambient air increases, the molecules of nitrogen free themselves more easily from the zeolite, which reduces the adsorption capacity of the device. While most oxygen concentrators rely on passive cooling for the device, our design uses the cool nitrogen exhaust in a heat exchange arrangement to actively cool down the zeolite and thus improve the devices power efficiency. Additionally, each of our cylinders makes use of todays very cost efficient sensor technology to monitor the humidity, temperature and pressure of each of our pressure vessels. If the ambient temperature affects the produced oxygen content, our device will automatically adjust parameters and accommodate for the change while staying within optimal efficiency parameters.
Price
Many of the people in need of our concentrators can not afford it. Our company is a purely not-for profit organization and to date is run exclusively by unpaid volunteers, which is why we can offer our device for its manufacturing cost. Currently we estimate our cost to be around USD 600 + shipping cost, which is in the lower range of oxygen concentrators. While there are cheaper devices, they will probably not last very long. We have designed our device for maximum resilience such that it will last for much longer and ultimately offer the best price per liter of oxygen on the market over its lifetime.
Dust & Dirt
One of the projects that our organization has been working on is a medical device framework we plan to make open source which facilitates the development of smart medical devices. Our oxygen concentrator leverages this framework to recognize when dust and dirt begin to block the inlet filter and initiate a self-cleaning routine on the next procedure. While we have yet to test this feature for effectiveness, we believe that this will at least reduce the frequency with which the inlet filters need to be cleaned and therefor free up the time of healthcare workers so that they can focus on what really matters.
Altitude
At high altitudes pressure and oxygen levels drop, which changes the ideal operating parameters for the device. Our concentrator contains an absolute pressure sensor capable of measuring approximate height and can therefor recognize a change in altitude and automatically adapt to the new environment.
Servicing
A recent study found that of 57 oxygen concentrators across 12 Nigerian hospitals, 24 devices were pumping out room air and only 3 were delivering medical grade oxygen.1https://onlinelibrary.wiley.com/doi/10.1002/ppul.24656#ppul24656-bib-0009 It is clear that natural resilience and ease of servicing are an important factor to make our oxygen concentrator a cost effective health investment.

Aside from humidity-related material exhaustion, the most expensive cause for failure is associated with the compressor driving the process. Our design relies on a Scroll Compressor which belongs to the most reliable compressors in the world. For example, one was used on the latest Mars Rover for this reason.

As mentioned before, our device has several sensors and uses a sophisticated software framework to contribute to its servicability. For example, the device monitors its internal operation in a so-called "digital twin" which allows us to provide error messages with much more detail that can help in the isolation of failure modes and consequently with the repair.

Additionally, our framework enables the development of complicated self-maintenance routines that could partially clean the device, measure oxygen efficiency and adjust parameters to adjust for age-related performance losses.

Finally, we plan to publish detailed, picture and video-based servicing instructions in several languages for our devices. Furthermore, since our device has wireless capabilities, we are considering creating a digital servicing record sheet accessible via any wireless device with wifi capabilities that servicing agents can use. We would like to hear from end users about the usefulness of such digital servicing records, if you have thoughts on this matter, please contact us!

Our Work Process and Progress

Our goal is to develop an oxygen concentrator that fulfills at least the optimal requirements of the target-product-profile and a target technical specification published by WHO and UNICEF. This includes the implementation and certification for various standards such as ISO13485, ISO60601-1 and related as well as approval by the FDA. These processes take a lot of time and require patience, especially when working with volunteers who need to be trained and have little time available. If you have the experience or means to contribute financially to our goal of hiring a small amount of full time engineers to accelerate our efforts, please consider to contribute.

Initial Research

What are the physics behind oxygen concentrators and how are current devices insufficient? What information exists and how large is the need?

Initial Design

First risk analysis, development of design inputs (user needs, compliance requirements...), preliminary specifications, design of pneumatic circuitry, electrical design, parts list with potential suppliers, development of software components and planning of a fully functioning development prototype.

Raise Funding for Prototype

Our volunteers have already put forth several thousands of USD for the proof of concept, printed circuit boards, pump prototypes, etc. but to complete the prototype phase an additional USD 5000 are required. If you can, please consider contributing so that we can continue our development.

Assemble and Test Prototype

Ordering parts from potential suppliers, assembling multiple prototypes, running test routines, and plotting operating parameters for different pressures, flow rates, temperatures, adsorbent materials and quantities, and looking for potential flaws in the concept.

Implement Design Control

Conclude development lifecycle in accordance with ISO 13485 quality management systems for medical devices, including detailed risk analysis, requirements management and design traceability for all parts of the system.

Plan Validation and Verification

Validate design through indepth review and write detailed test plans covering all requirements verification.

Raise Funding for Testing and Approval

Testing must be done through an independent laboratory and must be conducted with a prototype build with the parts manufactured with the final manufacturing method which requires some custom tooling. Certification for various standards and approval of the device also come with a heavy fee that must be financed.


ArdenMed wants to ensure that it's device will be a long-lasting investment and offer a long term warranty, which is only possible after extensive testing and design control.


Currently expected fundraising target for this phase: USD 80,000

Attain Certifications and Approval

Final review of design history file, manufacturing instructions, supplier quality contracts etc. Get audited for ISO 13485 and other standards as applicable (see below).

Launch and Post Market Monitoring

Begin manufactury, set-up support centers, provide training documents for servicing personnel, identify customers, gather feedback and general post-market surveillance.

Additional Information