Closer to the Patient: Miniaturization of Point-of-Care Testing Devices

According to the World Health Organization, the number of people aged 60 years or older will rise from 900 million in 2015 to 2 billion in 2050, accounting for more than one-fifth of the world’s population. At about the same time, the number of persons aged 80 years or older is expected to triple. To cope with the medical demands of a rapidly growing population of elderly people, medical product designers will strive to develop clinical diagnostic instruments and medical devices that are smaller, more portable, easier to use, and ultimately, located closer to the patient, whether at home or at the point of care.

Point-of-Care Testing

In vitro diagnostics (IVD) are tests done on samples such as blood or tissue that have been taken from the human body. These tests can be used for life science research purposes or to help diagnose and treat a patient. When used for clinical care, they are often referred to as clinical diagnostics.

Traditionally, trained personnel have conducted clinical diagnostic testing in centralized laboratories using large, complex, and expensive test instruments. More recently, diagnostic testing has been moving out of the central laboratory into testing sites that are closer to the patient, a trend often referred to as point-of-care testing (POCT). POCT locations include hospitals, physicians’ offices, clinics, pharmacies and even patients’ homes. Advantages of POCT include reduced complexity, rapid results, cost-effectiveness, accessibility, improved patient convenience, and reduced patient risk.

POCT instruments often use similar assays (testing procedures) as the central labs’ traditional instruments, but the POCT instruments are typically much smaller and easier to use. Ease of use is critical, since POCT instruments will be operated by people with widely varying levels of experience and training. In addition, POCT devices must be designed to perform similar process steps as central lab machines but must do so within a much smaller footprint. This design challenge has been met by reducing the volumes of biological samples and reagents needed to perform the assays, and by reducing the fluid handling requirements in the instrument down to microfluidic levels.

POCT instrument developers who employ solenoid valve technology to control the flow of fluids in their products can design the fluidic path to flow directly through an isolation valve or, alternatively, employ a general-service (air) solenoid valve as part of a microfluidic system design.

An isolation valve provides hermetic separation of the control mechanism and the fluid. If choosing an isolation valve, a designer should look for several critical characteristics. First, it must have a small footprint to reduce overall instrument size. Second, it must be able to operate with a very low internal volume, to allow for small sample sizes and low reagent consumption. Finally, power-saving features such as a latching coil or an integrated hit-and-hold circuit reduce power consumption and therefore reduce the potential for heat generation, which is important when a valve is processing with thermally sensitive samples.

As clinical diagnostic instruments get smaller and closer to the patient, new designs are increasingly moving away from traditional fluidic systems and toward utilizing microfluidics. To ensure that assays are conducted properly (without the presence of highly trained lab personnel), these designs often rely upon single-use microfluidic cartridges that are preloaded with the reagents needed to perform the assay. In POCT systems with this type of fluidic design, general-service (air) valves can be used to pilot or drive the mechanism that generates the movement of fluids (reagents, samples, etc.) within the cartridge and the POCT system in the proper sequence. Among the key features to consider in a general-service valve for POCT applications are 1) ensuring a high size-to-flow ratio, 2) minimizing weight, 3) high cycle life, and 4) low power consumption.

Home-Use Medical Devices

A home-use medical device is intended for use outside of a professional healthcare facility, such as in a home. The user can be the patient, a caregiver, or a qualified healthcare professional. Advantages of home-use medical devices include reduced healthcare system strain, improved patient convenience, and reduced patient risk. According to the U.S. Centers for Disease Control and Prevention (CDC), approximately 5 percent of hospital admissions result in a healthcare-associated infection. The COVID-19 pandemic increased this risk, particularly for immunocompromised patients.

Two examples of home-use medical devices are oxygen concentrators and dialysis machines.

Oxygen Concentrators. An oxygen concentrator is an oxygen therapy device that takes in and compresses surrounding air, then filters out nitrogen to provide oxygen-rich gas to a patient with below-normal oxygen levels due to a medical condition, such as chronic obstructive pulmonary disease (COPD). Oxygen concentrators have become a popular alternative to other forms of oxygen therapy such as compressed or liquid oxygen tanks because they are lighter and easier to carry, two factors that increase patient mobility. Home oxygen concentrators started out as what are now called stationary oxygen concentrators, which offered very little patient mobility. Later, portable oxygen concentrators were introduced, greatly enhancing patient mobility due to their relatively small size, low weight, and portable battery power.

Both stationary and portable oxygen concentrators typically use solenoid valves to control the flow of air into the unit and the delivery of oxygen-rich air to the patient. As portable concentrators continue to shrink in overall size and weight, developers continue to seek new flow-control solutions that provide high flows in very compact sizes. Besides a high flow-to-size ratio, other key features designers look for include low power consumption (to extend battery life), quiet operation (patient comfort) and extremely long cycle life (long-term reliability).

In addition to individual component features, oxygen concentrator manufacturers value supplier partners with the ability to provide custom solutions to match their unique space and mounting requirements, as well as extensive experience and knowledge of standards and regulations governed by the Food and Drug Administration in the United States and the Medial Device Regulation in Europe.

Home Dialysis. Dialysis is a treatment for kidney failure that filters a patient’s blood to remove unwanted toxins, waste products, and excess fluids. There are two types of kidney dialysis: hemodialysis and peritoneal dialysis. Hemodialysis filters the blood outside of the body through a dialysis machine, while peritoneal dialysis uses the lining on the inside of the abdomen, called the peritoneum, as a natural filter.

Traditionally, hemodialysis has been administered in a hospital or dialysis treatment center; however, home hemodialysis is rapidly growing as a treatment alternative for patients with end-stage renal disease (kidney failure). According to the National Kidney Foundation, home dialysis offers many benefits to patients including reduced medication and improvements in energy levels, sleep quality, and overall quality of life.

Newer home dialysis equipment being developed is typically either hemodialysis or a specific type of peritoneal dialysis, called automated peritoneal dialysis. Both types typically utilize solenoid valve technology. The valve technology type used depends on whether the valve is being used to directly control the flow of fluids or if it is being used to pilot a mechanism that controls fluid flows.

For applications where the fluids (blood, dialysis fluid) are directly controlled by the valve, a designer can choose the previously mentioned isolation valve technology or use a pinch valve. A pinch valve is a device that opens and closes the flow path by pinching disposable tubing. Although not typically referred to as an isolation valve, a pinch valve performs a similar function by isolating the valve mechanism from the media through use of the tubing.

As new home-use dialysis machines are developed, a general-purpose (air) valve is often used as a pilot valve. As these machines become smaller and more portable, developers continue to seek new flow-control solutions that provide high flows in very compact sizes. Besides a high flow-to-size ratio, other key features that designers look for include low power consumption, quiet operation, and extremely long cycle life.

The global market for both point-of-care testing instruments and home-use medical devices is expected to grow rapidly over the coming decades. To meet this demand, developers will continue to design products that are smaller, less complex, and easier to use. As global demand increases, choosing the right supplier partner is critical. Along with component features, developers should consider the supplier’s application expertise, global reach, and localized manufacturing and support, which are all key advantages for developers bringing diagnostic instruments and medical devices closer to the patient.

This article was written by Jim Perry, Director of Business Development, Emerson Discrete Automation, Analytical and Medical, St. Louis, MO. For more information, contact This email address is being protected from spambots. You need JavaScript enabled to view it. or visit here .

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