(H-310) Sensor Chip Programming for the Prevention of Wheelchair Pressure Ulcers

Pressure ulcers, otherwise known as bedsores, are skin and tissue injuries resulting from prolonged pressure on the skin. When developing a pressure ulcer, the skin and tissue break down because of the prolonged pressure which cuts off vital blood flow to the area. Individuals with limited mobility are most vulnerable to developing pressure ulcers due to their inability to switch positions to increase blood flow such as wheelchair users or those in hospital beds. A study run by the US Department of Veteran Affairs recorded the time spent in the mobility device of full-time wheelchair users throughout their day and found that on average users were spending 10.6 +/–3.0 hours in their chair. The recommended pressure relief frequency for ulcer prevention is 15-second shifts every 15 minutes and yet users spend 2 hours a day on average in static positions. Standard wheelchair cushions are provided by insurance but fail to disperse pressure over long periods of time. There are over 3 million full-time wheelchair users in the United States, those who are unable to shift weight themselves can choose between costly hired assistance and expensive automated wheelchair cushions. The cost of specialized wheelchair cushions can be prohibitive for many individuals, especially those with limited financial resources. Therefore, there is a need for an affordable and effective device that can provide consistent pressure relief for individuals with limited mobility.

A comprehensive literature review and extensive market analysis were conducted to gather vital information for the compilation of a detailed feature list and cost evaluation of potential competitors in the field. The primary focus of the research was to identify the key requirements of the device based on its physiological impact and user benefits. From the literature review, it was determined that the device must be capable of redistributing 90% of the user's weight for 15-second intervals, repeated four times every hour. A study determined that a pneumatic system equipped with four equidistant extension points achieved the desired relief effectively. Once the physiological requirements were well established, the feature list was further refined to remove extraneous features and lower pricing. The device was determined as a Class I device since no biological data was recorded but would require a 501(k) notification and a fee of $4967 to be paid to the FDA since the intended use of our device is to prevent the formation of pressure ulcers which can be considered “...a use of substantial importance in preventing impairment of health…” (FDA). Our design process was followed by a patent search in the field to ensure that the design did not infringe on any existing intellectual property. In addition, the regulatory requirements set forth by the FDA were followed closely to ensure that the device could be classified as a Class I medical device. These considerations demonstrate the marketability and intellectual property protection of our device

The novelty of our device comes from the ability to transform a regular wheelchair cushion into an automated pressure relief system without having to buy a separate cushion with pneumatic relief embedded into the device. The device consists of a microcontroller, air compressor, and a base with a 4x4 array of connection ports for the individual units. Each unit contains a pressure sensor to implement the recommended pressure relief frequency. Users can buy units as needed and connect them in predetermined patterns in order to fulfill their personal needs. A study that took the pressure distribution of a patient in wheelchairs, determined that pressure relief can be achieved by tilting the patient in two axes. This could be achieved by using a simple four-unit configuration, However, a more advanced pressure relief system could be achieved with the introduction of more units. During the design of this device, four design features stood out: the circuitry, the algorithm, the unit design, and the node connectors.

The base of the device was designed to be a 4 by-4 array with a relay system running through each node. Units snap-fit into place for user ease which would signal to the microcontroller that an extendable unit was in the corresponding node. Through this mechanism, the microcontroller will identify the current setup and determine which units should inflate. By including the pressure sensor and solenoid valve in the extendable unit, there are no superfluous components included in the base. This design choice allows for a cheap base with extra costs being wrapped in the separately sold units. A cover would go around the user’s wheelchair cushion with an elastic band running through our base. This would ensure that with the extension and retraction of the pressure units, the entire system would remain sturdy and minimize the chance of disconnection within the device.

Acknowledgements: To everyone involved in the MINDS program and to Alicia Fernandez-Fernandez, Dr. LaMack, and Dr. Hollins.