Medical Electronics
The challenging environment of medical device electronics
By Russell Overend, managing director, Wideblue Russell Overend D
esigning electronics for the medical device sector is complex and challenging. As medical devices can be used in life or death situations the sector is heavily regulated and rightly so. The key piece of legislation is the EU Medical Device directive which all manufacturers must comply with in order to legally design and manufacture any medical device. A CE mark on the equipment shows that the provisions of the directive have been complied with For those wishing to market into the USA there are separate FDA laws to be complied with.
There are currently changes underway which are causing a large backlog in regulatory approvals. The Medical Device Directive is being replaced by the new Medical Device Regulations. This will require additional or new certification for existing products. Some notified bodies have announced their intention to exit the CE marking review process. Post- Brexit companies selling medical devices in Europe fear their current notified body certification may no longer be valid. Many UK companies are now registering with EU notified bodies. All of these factors are driving up delays, worry and expense for regulatory compliance of medical devices. Those seeking to place a new medical device on the market should therefore seek specialist help well in advance of any application. Wideblue work with clients across a wide range of medical devices we are seeing some common trends in the development of our new medical devices: 1. Devices are becoming ever smaller and battery powered meaning that more energy efficient electronics have to be packed into smaller spaces leading to greater miniaturisation of electronic components. 2. Most new devices have wireless or bluetooth capability built-in where data is being transmitted to a nearby device, server or remote site. Data security, encryption and patient confidentiality is a key consideration as patient data can be transmitted across multiple nodes. In terms of wireless network choice there is a trade off between speed, reliability and longevity, 5G might be fast but 2G could be more reliable and available in some parts of the world.
3. Battery sizes are also becoming smaller but there is often a trade off between size, cost and capacity. However, battery technology is advancing rapidly and in future this will not be such an issue. 4. If the device is to be worn by the patient (eg health monitoring equipment) it must be small, comfortable and unobtrusive. 5. Clients are looking for multiple functions to run off one device. There are multiple low cost sensors and low cost memory which can enhance a medical devices functionality or help with a new products post marketing surveillance requirements. Wideblue often add an “engineering function” to new devices that log useful (non confidential) data. Structured properly, this data can help demonstrate compliance with post marketing surveillance responsibilities eg logging number of times used, battery voltage, ambient temperature / humidity, device performance and attempted misuse is considered best practice to monitor how a new device is performing and actually being used.
6. If a device is reliant on the internet to operate one must be conscious of denial of service either though lack of signal or through attacks and needs to be considered in the product’s ISO14971 risk assessment.
Case Study: N-Tidal Personal Capnometer Many of the above trends were evident in a project we carried out recently to design and develop the world’s first personal capnometer. A capnometer is a device used to measure the amount of CO2 in a exhaled breath to assess the patient’s lung health. Traditionally the device is a large bedside machine used in hospitals. We were asked by Cambridge Respiratory Innovations Limited (CRiL) to design a
hand-held, battery-powered device which would carry out the same function for use by patients in their home, by GPs or respiratory specialists. An ergonomic study allowed us to develop the device for children and adults and left / right handed operation. We choose an infra-red LED tuned to the peak CO2 adsorption wavelength and developed some patented infra-red optics to measure the CO2 levels as the patient breathes in and out through the mouthpiece. We had to use miniaturisation techniques so that the sensor could be located directly in front of the mouth as it would produce more accurate results. A replaceable breath tube with integrated infra red window means the device can be used by many patients and prevents cross- contamination. A simple traffic light system (red, amber, green) gives an indication of the lung health so that any remedial action can be taken quickly. Electronics within the device capture the data from the sensor and the breath record is transmitted wirelessly to a secure server. Not patient identifiable data is used. Additional engineering data is captured and transmitted to allow us to monitor the use of the device in service. We chose 2G comms as this service was most available in most of the target countries and the service is unlikely to be switched off due to the installed base of other 2G devices. The device uses an internal rechargeable Li ion battery charged through a USB connector. This had the added benefit during development and clinical trials of having direct access to the microprocessor and memory in the device. The N-Tidal Capnometer is currently undergoing clinical/user trials and has already produced superb clinical results. Subject to successful completion of these trials and regulatory approvals, the device is expected to go into commercial production in 2020.
wide-blue.com 14 December/January 2020 Components in Electronics
www.cieonline.co.uk
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