Interconnects in Healthcare: Enhancing Medical Devices and Patient Care

Medical equipment and medical devices are subject to some of the most stringent standards. This is necessary to ensure both operator and patient safety. The medical device industry is constantly evolving with innovations in materials, wireless technologies, sensor technologies, packaging, power devices, and so on. However, despite the ongoing innovations occurring in the electronics of medical devices, it is critical that all equipment continues to follow regulatory compliance.

The various connectors that are designed for medical systems are subject to the very same regulatory scrutiny while also evolving in terms of size, power density, and construction. Outside of meeting the required medical standards, connectors used within medical applications are often met with design constraints from moisture ingress, chemical exposure, and mechanical stresses such as vibration and shock. This article discusses current trends in medical devices and equipment, as well as the design considerations that arise with technological enhancements such as innovations in MEMS, wirelessly enabled patient care, and AI/ML.

The range technologies used in medical equipment

Medical equipment can operate with a combination of mechanical, hydraulic, pneumatic, electronic, digital, optical, and radiological principles, so the connections between systems can vary significantly. Examples of larger medical equipment might include blood analyzers, X-rays, CAT scanners, ultrasound equipment, diagnostic cardiology equipment, MRI machines, heart-lung support systems, and patient-monitoring systems. Examples of small form factor electronics include implantable medical devices such as cardioverter defibrillators, pacemakers, cochlear implants, and intrauterine devices (IUDs). Wearables are also a subset of medical technology where devices such as ECG patches, blood pressure monitoring, wearable spirometers, and smart clothing/watches can be used to track and monitor a patient’s vitals. The wide range of modalities found in medical equipment require many connector technologies to support them.

This can be seen in Figure 1 with a disassembled ultrasound transducer with a bundle containing hundreds of micro-coaxial cables for 2D arrays. This type of equipment uses the ultrasound imaging modality, where short acoustical pulses penetrate multiple interfaces and the echoes transmitted back are converted to electrical signals via the transducer to produce 2D images.

Figure 1: Disassembled ultrasound transducer with a 128 micro-coaxial bundle. Source: [1]

Blood analyzers will use hydraulic lines and valves to move samples to various parts of the machine and mix them with various reagents to perform tests. An MRI produces a detailed 3D anatomical image by both exciting and detecting the change in the direction of the rotational axis of protons found in the water of living tissue. This is accomplished through the use of a pulsed RF current in tandem with powerful magnets that produce a strong enough magnetic field to force the protons in the body to align with that field. This allows users to observe the difference between various types of tissues based upon their magnetic properties.

Wearables leverage a number of micro-electro-mechanical system (MEMS) sensors and actuators and wireless technologies in miniature form factors. An example of an implantable device using MEMS is cardiac implants that control thermoresponsive actuators — such as shape-memory alloys (SMAs), a type of smart material that responds to temperature ― via an RF connection to address the recoil issue associated with stents. Implantable drug delivery microsystems can be electromagnetically actuated and wirelessly operated using a tuned RF field.[2] Wearables often rely on MEMS sensors that use technologies such as silicon-based strain gauges to measure pressure, acceleration, or orientation to measure parameters such as heart rate, SpO2 levels, movement, and a chemical analysis of body fluids. The sheer range of technologies used to monitor, analyze, and treat patients is vast, where device form factors are constantly shrinking to better suit the application. This requires shrunken electronics where everything is designed with space in mind (e.g., traces are closer, usage of smaller SMT components).

Trends in medtech

The megatrend of IoT has permeated into the medical industry, where all data can be monitored and tracked remotely. This opens many doors for prevention and early detection in patient care, as it lowers the barriers to test and lowers the access barriers to many types of diagnostic equipment. Wireless technologies, such as 5G, allow for near-real-time monitoring and control to potentially detect an acute condition and perform an emergency response (e.g., defibrillation in the event of cardiac arrest). Higher-bandwidth communications are also necessary to, for instance, readily send and receive large files such as imaging results to other relevant departments (or upload them to an electronic health record system), resulting in a quicker turnaround of critical information. High-bandwidth, low-latency communications are critical for potential telesurgery (remote surgery) applications that might use AI to interpret feedback from haptic technology used by a surgeon located away from the robot.

AI has the ability to truly augment medical processes for more efficiency, accuracy, and control with many potential use cases. AI can be applied for data interpretation to, for instance, list out potential diagnoses. Other applications include intelligent prostheses for the disabled, the labeling of imaging results (X-rays, MRI scans, etc.) for various exams, or to spot abnormalities or quickly identify negative exams.[3]

A bird’s-eye view of medical connectors

As technology in medical devices evolves, so do the connectors used within them. Many medical connectors must be certified according to specific standards. This is the case for small-bore connectors (ISO 80369-1) for tubing, syringes, and other accessories that deliver fluid. Other subcategories for small-bore connectors include respiratory/breathing system connectors (ISO 80369-2), enteral and gastric connectors (ISO 80369-3), urinary collection (ISO 80369-4), limb and cuff inflation (ISO 80369-5), and more. Other specific medical connector standards include the four-pole connector system (ISO 27186) used in active implantable cardiac rhythm management devices.

Most connectors will require compliance with the IEC 60601-1 standards to prevent harm to either the patient or operator. These connectors are frequently handled by medical personnel and are often in direct contact with the patient — they therefore require polarization of the connector head as well as the ability to visually differentiate between connectors in order to prevent mismatches and possible disastrous consequences (e.g., device socket outlets that can’t fit with main plugs). If the detaching of a connector is dangerous (e.g., nerve and muscle stimulator, dialysis machine, laser device), it must be prevented by some mechanism such as locks. ISO 60601-1 standard also specifies the maximum leakage current that flows from the probe contact to ground through the patient as well as minimum creepage and clearance distances to ensure a high degree of isolation. As shown in Table 1, these are classified into three categories: body (type B), body floating (type BF), and cardiac floating (type CF).

Table 1: Medical device categories, according to IEC 60601-1.

More niche electrical connections might include the pin-socket or magnetic snap-ons in wearables, or the ultrasound transducers mentioned earlier with hundreds of pins in a micro-coaxial bundle. These are specifically designed to serve their function and may be difficult to categorize under some of the established medical standards. There are also the more standard electrical connectors that are often used in medical equipment. Electrical connectors generally fall into one of three categories:

• Board-to-board
• Wire-to-wire
• Wire-to-board

Figure 2 shows board-to-board, wire-to-wire, and wire-to-board connectors offered by EDAC and how these connectors can be installed. Board-to-board connectors connect PCBs together. Examples of this include card-edge or header connectors that can mate multiple PCBs. Wire-to-board solutions will connect wires to the PCB via a board-mounted connector head; these are often spotted at the edge of the PCB so that they can be accessed on a rack. Wire-to-wire connections are generally male- and female-type connector heads that mate directly together, thereby connecting wires.

Figure 2: An illustration of many of the board-to-board, wire-to-wire, and wire-to-board connections offered through EDAC.

Many of the connectors in Figure 2 have applications in medical equipment. For example, card-edge connectors are often used in portable embedded computers to connect expansion cards, memory interfaces, and data acquisition (DAQ) cards. Header connectors are nearly ubiquitous for connecting from one PCB to another via a ribbon cable. EDAC's inline connectors are waterproof wire-to-wire and wire-to-board solutions that simplify the installation of a signal connection in wet environments. D-subminiature (D-sub) connectors are used for serial communications to, for instance, transmit and receive information to and from the sensors and actuators within medical equipment. RJ45 and USB connectors are necessary interfaces in all types of medical devices from diagnostic cardiology to patient monitoring.

Enhancing connectors for medical applications

Much of the demands on medical connectors has to do with miniaturization and ruggedization. Many medical systems/devices are shifting toward portability, with a focus on wirelessly enabling patient monitoring. This trend requires all aspects of an electronic system to be space-optimized, including connectors. Medical devices will always have the requirements of safety and reliability, such that the device can withstand the medical environment (e.g., vibration from movement, fluid/chemical splashes, EMI protection). EDAC has connector options that meet these demands within medical applications.

Miniaturization and densification

In order to match pace with the miniaturization of medical devices, connectors are often found integrating multiple power-, signal-, and even RF-type connections within a single connector to minimize connector footprint. This can be found in EDAC’s power-combo D-sub connectors that allow for both power (10, 20, 30, or 40 A) and signal connections (5 A) in 22 different configurations (Figure 3).

Figure 3: The EDAC power-combo D-sub connectors with both power and signal connections to save on board space.

Other high-density connectors might include EDAC's rectangular connectors that feature up to 120 contact positions for mates that require hundreds of signal connections (Figure 4).

Figure 4: EDAC rectangular connectors with up to 120 contact positions featuring a unique hermaphroditic contact design that ensures a high-reliability connection.

Ruggedized connections

Another aspect of medical device design is the potential strain the connector head undergoes. This could be in the form of water ingress from either a high-humidity environment or from direct exposure to fluids. This is not unusual in a medical environment, where fluids need to be extracted and tested (e.g., blood analyzer). Other stressors might include mechanical strain from vibration or shock. This type of stress could occur with daily wear and tear from operator handling or even from the proximity of a connector to a motor. A centrifuge, for instance, will rely on a motor to perform the required rotations. Many medical connectors must transmit at high signal speeds, endure frequent mating cycles and sterilization, and work with sensors.

EDAC offers waterproof and vibration-resistant inline, D-sub, USB, and HDMI connectors with up to an IP67 rating (Figure 5). This means that these connectors are entirely dust-tight and can also be submerged in up to one meter of water. The vibration resistance comes from well-designed mates with a high retention force with either a bayonet-style, threaded, or locking mate. This opens up the potential medical applications these industry standard connectors can be used in. In fact, most of the connectors offered through EDAC have options for a more ruggedized connector solution outside of the standard constructions.

Figure 5: IP67-rated D-sub, USB, HDMI, and inline connectors offered through EDAC.

EDAC meeting the needs of medical applications

Medical electronics span from massive MRI scanners to implantable devices that are smaller than a fingertip. Medical devices range in size, integrated sensor and actuator technologies, and implementations. This calls for myriad connectors to meet the task of transmitting critical data for processing. EDAC offers a range of connectors that are optimized for medical environments, ensuring the connector functions during the lifetime of the device.

References

1. Culjat, M., Singh, R., & Lee, H. (2013). Medical devices surgical and image-guided technologies. Wiley.
2. Mohd Ghazali, F.A.; Hasan, M.N.; Rehman, T.; Nafea, M.; Mohamed Ali, M.S.; Takahata, K. MEMS Actuators for Biomedical Applications: A Review. J. Micromech. Microeng. 2020, 30, 073001.
3. Amisha, Malik P, Pathania M, Rathaur VK. Overview of artificial intelligence in medicine. J Family Med Prim Care. 2019 Jul;8(7):2328-2331. doi: 10.4103/jfmpc.jfmpc_440_19. PMID: 31463251; PMCID: PMC6691444.