Developing medical sensors compliant with global requirements
Many technology trends in the medical device market are global, including miniaturization, low power consumption and liquid media compatibility; however, materials compliance, product requirements, and cost issues can vary from country to country.
This translates into the need for sensor manufacturers to provide flexible and scalable product lines to meet global requirements. They also have to ensure quality of product and quality of supply. To meet the requirements of global medical device makers, sensor manufacturers need to consider four key issues – miniaturization, materials and regulatory compliance, supplier quality assurance, and service and support.
Miniaturization affects size, portability and weight
Medical device designers are faced with the challenge to develop smaller, lighter and more portable equipment to save real estate in patient rooms and to allow medical professionals to move equipment from room to room. Equipment that benefits from miniaturization includes infusion or insulin pumps as designs move from bulky to portable and ambulatory models.
By providing smaller size options, a sensor can be more easily integrated into space-constrained infusion pump designs, as an example. Small size and low power consumption helps improve a patient’s quality of life by increasing the portability of the infusion pump.
There also is a trend by healthcare providers, particularly in the United States and the European Union, to transition patients from in-hospital care to home-care treatments. This also drives the need to miniaturize medical devices including respiratory and diagnostic equipment.
In some cases, miniaturization allows for some diagnostics to be built into networked medical devices to monitor a patient’s care remotely. As a result, sensors that integrate multiple functions, such as temperature and humidity sensing, in a single package will be required. This will free up board space to reduce the size of the medical device or allow for higher functionality. Medical devices that can benefit from integration include respiratory therapy, including ventilators and sleep apnea machines.
Another way sensor manufacturers meet these needs is by developing sensor lines that offer a number of options for mechanical interfaces, mounting styles, packaging and I/O options. This allows medical device designers to select the right interface to help them reduce space, cut costs and eliminate the need for additional components. As an example, pressure sensors should offer multiple mounting options to accommodate placement in space- constrained applications, so the designer can position the sensor exactly where it needs to be for accurate and precise measurement. This is vital in applications such as dialysis treatment where accurate and precise measurement of the dialysate and venous pressure is critical to a patient’s safety.
Particularly for portable applications, sensors should meet low voltage and low power requirements for longer battery life. They should also provide wake-up/sleep modes, so the device is not consuming any power until it’s switched on again. Sleep mode can help extend battery life, reduce the size of the power supply, and thus the weight of the medical device.
Materials/regulatory compliance affect global manufacturers
In the European Union (EU), for example, government regulators are much more likely to ban a substance based on a small amount of data that indicates it can be harmful or hazardous. While the EU is a big market for medical devices with its well-funded / high-quality healthcare systems, device manufacturers must ensure that their products meet EU regulations before they can operate in that environment.
Two regulations that impact the global electronics industry include the “Restriction on the Use of Certain Hazardous Substances (RoHS) Directive”, which aims at restricting the levels of six chemicals historically used in electronics manufacturing, and the “Registration, Evaluation, Authorization and Restriction of Chemical Substances” (REACH) regulation, which provides the framework to hold the industry responsible for controlling its use of hazardous substances in the EU, affecting materials use in end- products and manufacturing processes. If global manufacturers and resellers want to sell into the EU, they must comply with these regulations.
Sensor manufacturers have to be fully informed of materials selection, supply chain and manufacturing processes to ensure that they adhere to European material compatibility regulations. This is particularly important for sensors as they often come in contact with a patient’s air or fluid pathways, because sensors need to be positioned as close to the fluids (blood, infectious materials, saline, etc.) as possible to ensure the most precise and accurate measurements.
This also drives the need for RoHS-compliant liquid media compatible sensors for medical equipment ranging from chemical analyzers to ventilators. And since cost is always an issue, the sensor product line also needs to offer a variety of options for characteristics such as outputs, pressure types, pressure ranges, mounting options and packaging styles to meet country requirements.
Product platforms that offer multiple options and parts to meet country-specific requirements also help engineers meet price points set in different regions of the world. It also allows them to scale up or down, depending on the application and country requirements.
Figure 2: Honeywell’s HumidIcon digital humidity/temperature sensors provide two functions in a single small package and operate down to 2.3Vdc.
Supplier quality assurance is critical
Not only do sensor manufacturers have to meet a variety of materials regulations, and global electrical requirements, including UL in the United States, cUL or CSA in Canada, ENEC in Europe and CQC in China, they also need to have quality assurance systems in place to ensure chain of custody and quality control.
Suppliers should meet Six-Sigma quality standards in their manufacturing processes to ensure high quality products. This is critical for any medical device manufacturer since their products can impact a patient’s safety.
Reliability of supply also is important to designers. sensor manufacturers should have a global presence to support design and production requirements. As an example, European designers often will develop a product that requires several modules or subassemblies that are typically outsourced to electronics manufacturing service (EMS) companies in different parts of the world. The modules or subassemblies are then shipped back to the manufacturer in Europe for final assembly.
Emerging technical trends
Medical device engineers also require suppliers to provide product support for emerging technical trends. A few examples include digital interface options and single-use sensors. sensor manufacturers are offering digital interfaces, particularly I2C outputs, for a few reasons. A digital I2C output allows designers to eliminate signal conditioning circuitry from the printed circuit board (PCB), which saves board real estate and costs related to the signal conditioning. It also reduces the amount of copper traces and wires for a further cost savings. The fewer components on the PCB allow for miniaturization.
The on-board signal conditioning provides the sensor’s compensation, calibration and amplification. This delivers higher accuracy and reliability, which contributes to patient comfort and quality of care. It also lowers the overall cost of ownership for the medical hospital or clinic. This can benefit a wide range of applications from dialysis machines and infusion pumps to incubators and respiratory equipment.
There is also a growing trend for single-use sensors in applications such as infusion pumps to eliminate the need to clean areas that come into direct contact with medicated or patient fluids. However, medical practitioners should take into account the reliability of single-use sensors as the performance of the sensor can be a determining factor in how well the equipment performs for the patient.
Cross contamination is a big concern in systems intended for single-use, when the sensor is not changed with every patient when it’s supposed to be. This is especially true for devices used with patients with illnesses such as HIV/AIDS, the bird flu and Legionnaire’s disease that are transmitted by bodily fluids. While medical device manufacturers recommend using one sensor per patient when using single-use sensors, there is the risk of multiple use at clinics in areas that also face budgetary issues combined yet with fewer regulatory controls.
About the author
James McKenna is Product Director in EMEA for the Pressure and Thermal product portfolio of Honeywell Sensing and Control, a manufacturer of sensors and switches within the ACS Strategic Business Group. More information about Honeywell and its technologies can be found at https://sensing.honeywell.com/.
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