Challenges in Medical Electronics

Article By : M. Di Paolo Emilio

Electromedical devices for diagnosis and the treatment of numerous diseases must meet particularly strict quality, reliability, and safety requirements.

Progress in electronic technology has made it possible to create increasingly safe, compact medical devices with the lowest degree of invasiveness, but there are still challenges that include meeting strict safety standards, providing wireless connectivity, and operating with highly constricted power budgets.

An electromedical device is defined as an electronic device with a part that can be applied directly to the subject or used to transfer energy to or from the patient. Applications include diagnosis, treatment and monitoring of the patient’s health conditions, but also alleviating or even eliminating pain.

Challenges to face

Safety, both for the patient and healthcare professionals, is the first requirement that an electromedical device must comply with. The IEC 60601 family of standards sets the requirements for safety, performance and electromagnetic compatibility of electromedical equipment. Compliance with IEC 60601 standards can only be achieved through careful evaluation of all phases of the product development cycle, starting from the selection of the components.

Electrical insulation is directly connected to the issue involving safety. To meet the stringent requirements imposed by regulations, it is in fact necessary to guarantee high galvanic isolation of the circuits in the equipment, using barriers or other protection solutions such as optocouplers or transformers. In addition, leakage currents must be minimized — and better yet eliminated.

The highest level of risk occurs for class III electromedical devices and active implantable devices (AIMD) such as pacemakers and artificial hearts. Other medical electronic devices, with lower risk classes (classes IIa, IIb and class I) are represented, for example, by X-ray diagnostic equipment, surgical lasers, ultrasound equipment, up to digital clinical thermometers.

The spread of the Internet and IoT infrastructure has paved the way for devices that monitor patients’ vital parameters, or schedule or control the administration of drug doses. Solutions of this type have made it possible, on the one hand, to achieve considerable savings on health-related expenses, and on the other to improve the efficiency and quality of the therapies provided. The key factors for the success of these innovative systems are connectivity and wearability.

Wearable devices

A wearable electromedical device is an autonomous, non-invasive device capable of performing a specific medical function (such as monitoring or dosing drugs) over an extended time. The term wearable implies that the equipment must be supported directly by the human body or by clothing.

Wearable devices, which have had exponential growth in the last decade, can be grouped into three categories: monitoring devices, rehabilitation devices and wearable medical aids. The last category includes all devices designed to provide long-term care to patients with temporary or permanent disabilities.

Measurements and vital signs that can be monitored include electrocardiograms (ECG), respiration, body temperature, heart rate, blood pressure, blood oxygenation, body movements and more. Thanks to the use of these medical aids, it is possible to provide timely assistance if any of the vital parameters are abnormal, helping to save lives.

Wearable medical devices represent important challenges for electronic designers, however.

Power absorption must be kept to a minimum, guaranteeing long battery life to the battery-powered device. This factor influences the choice of components, orienting towards low-power solutions with the possibility of operating in low absorption sleep mode. The mechanical constraints, related to size and weight, also affect the design activity by favoring the use of low-profile miniaturized components mounted on extremely compact PCBs.

Another important requirement for wearable electromedical devices is the connectivity: through a Bluetooth interface (typically BLE), mobile network or WiFi, it is possible to connect to an application or gateway which is capable of acquiring sensor measurements and remotely control device operation.

Connected devices

Connectivity is not a prerogative of wearable devices but concerns a wider category of electromedical equipment. The market for connected electromedical devices is booming, but that underscores the need to increase efficiency, reduce the costs of therapeutic treatment, and improve the treatments provided to patients.

Electromedical devices relying on IoT infrastructure allow patients to be discharged more quickly, or even avoid hospitalization, reducing healthcare costs. Healthcare devices such as insulin pumps, defibrillators, CPAPs, cardiac monitoring devices and oxygen cylinders can now integrate remote monitoring functionality, providing patients and caregivers with valuable real-time information without being tied to a hospital or healthcare facility.

Connected medical devices must be able to connect to the cloud infrastructure of the healthcare system and must, therefore, be equipped with a reliable antenna and network interface. A critical factor, often underestimated by companies that intend to place connected electromedical devices on the market, concerns the certification processes of wireless devices. In North America, for example, certification is separate from FDA tests and is required for all wireless devices.

Regardless of whether a device is totally new, or is the retrofit of an existing device to which connectivity has been added, it is necessary to go through a rigorous certification process not only FCC and CE but (if using the cellular network), even with the mobile network operator.

Components for medical applications

Even if each electromedical application has different requirements, there is a common need to use microcontrollers capable of providing high performance in terms of processing times, reliability, safety, absorption and connectivity.

The explosion of connected devices is favoring the introduction of cybersecurity mechanisms implemented at the chip level. Lately, the demand for ultra-low power microcontrollers equipped with analog peripherals has been growing. Benefits include high reliability, low latency, reduced noise and lower costs, particularly significant in devices such as glucometers, heart rate monitors and implantable devices. An example of a low-power microcontroller with integrated analog peripherals is the Renesas Electronics Corporation Synergy S1 series of MCUs.

The Synergy S1 series devices (Figure 1) include a 48MHz Arm Cortex-M23 core with safety functionality, equipped with programmable analog peripherals for signal acquisition and conditioning.

Figure 1: the Renesas Synergy S1 MCU series

Figure 1: the Renesas Synergy S1 MCU series

Texas Instruments offers a wide portfolio of low absorption solutions with analog front-ends that are particularly suitable for electromedical applications. An example is the combined high-performance Wi-Fi / Bluetooth module , based on proprietary WiLink technology. This solution allows you to add WiFi (2.4 and 5 GHz) and dual-mode Bluetooth 4.2 to an electromedical device.

WiLink series modules can be directly connected to a host microprocessor (MPU) via the serial interface (Figure 2). The WL1837MOD device from the WiLink ™ series offers the highest level of safety available, thanks to the FIPS 140-2 Level 1 certification which allows it to be used on hospital electromedical devices.

Figure 2: block diagram of a WiLink ™ combo device

Figure 2: block diagram of a WiLink combo device

Another fundamental component of electromedical devices is represented by the DC-DC converter, which must have high insulation characteristics. An example is given by the converters of the REMOM series of RECOM Power, equipped with250 VAC insulation with continuous operation and a creepage/clearance distance being greater than 8mm. REMxE converters are equipped with single or dual output, protection from short circuits, overcurrents, overvoltages and Under-Voltage Lock-Out (UVLO). The leakage current of only 1 µA makes these devices ideal for electromedical applications.

The primary constraint of thin, small and lightweight wearable devices will always be battery life. Conventional batteries such as lithium-ion (Li-ion) batteries may be suitable for such devices.

However, there are also other challenges. One of them is safety and security. Your Internet connection will expose data collected by your medical device for a potential breach. This problem becomes serious in the medical device industry as the data may represent a privacy violation or an impediment to correct measurement and misanalysis.

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