The push for miniaturization in medical devices is very apparent to manufacturers in all sectors of the industry. However, this trend is closely coupled with the goal of also making these smaller devices portable. From diagnostic instrumentation to handheld ultrasound technology, these two innovation drivers are shaping the devices coming out today as well as future products.
Tom O'Dwyer is the healthcare team technology director at Analog Devices. He oversees efforts to identify and develop technology that addresses the emerging needs of the medical market, including laboratory equipment, imaging, patient monitoring, consumer healthcare, and implanted devices. O'Dwyer can be reached at email@example.com.
In the world of medical devices, it seems smaller is more beautiful. Across all sectorslaboratory equipment, imaging, and patient monitoringthe market has seen a plethora of product announcements in recent times that herald a new era in size and portability. While research teams continue to drive forward the technical performance levels of large equipment such as imaging systems, the parallel move to portable versions marks a significant new direction for both the traditional large players and newer incumbents.
Instrumentation Moves Out of the Lab
The strongest push is from the consumer side to drive down cost, improve convenience, and provide more timely, accurate results all at once. Whenever a patient can perform a prescribed test at home and avoid travel to a medical facility, all parties benefit. Portable glucose meters are a prime example, with over 40 million units sold annually and an attendant revenue of $10 billion in disposable strips.
A second driver relates to sample integrity. It's true that laboratory equipment gives high precision results, but a major difficulty relates to how the sample is obtained. For example, consider blood coagulation testing. This is a necessary periodic test for patients on anti-coagulation therapy, and usually requires the patient to visit a local clinic where a blood sample is taken. As soon as the blood is drawn, it automatically starts to change its biological and chemical characteristics as it begins to coagulate. To prevent this, the sample must be adulterated with an anti-coagulanta necessary, but undesirable action. The sample must then be shipped to the test laboratory, where it can pass through uncontrolled environmental conditions, such as wide swings of temperature, humidity, and mechanical movement, that can impact the sample integrity. All of these sample concerns can be overcome by a miniaturized handheld version of the test. Blood coagulation testing has now become a simple, easy-to-use home test, using a new generation of portable systems, such as the Hemosense INRatio. By taking a single drop of blood placed on the temperature-controlled test strip, the instrument performs the test and produces the result on the spot.
Technology EnablersWhat has enabled this massive reduction in size? Certainly the cost reductions driven by Moore's Law and mass markets, such as mobile phones, have played an important role on the electronics side. Displays, processors, and memory have all come down in price along with high performance data converters and amplifiers. There are also important breakthroughs on the biological and chemistry side. The industry's greatly increased understanding of the sample chemistry, as well as its preparation, separation, and flow dynamics have all contributed to easing the task of diagnostic assay design.
Miniaturization: New ChallengesThis trend towards miniaturization, while greatly improving the convenience, quality, and accessibility of healthcare, has raised a different set of design challenges. The skill level of the person carrying out the test is an important consideration. The diagnostic must be designed to be procedurally very simple so that it can be performed by an elderly person with poor eyesight and limited dexterity. In the U.S., this means that, in practical terms, it must satisfy the conditions required by the Clinical Laboratory Improvement Amendments (CLIA) so that it can be CLIA-waived for use by non-technical people in the home environment. As an example, a major design goal of portable systems is to eliminate the need for user-performed calibration. If the user forgets the calibration step or does it incorrectly, incorrect results will follow with potentially serious consequences.
The Signostics palm-sized ultrasound productthe Signos (Figure 1)has quality image resolution with a touch-screen display, a start time of less than one second from sleep mode, and stores up to 10,000 images. Weighing approximately a half pound with a compact design that fits into the palm of the hand, the product is equivalent to the size of a smart phone. This allows physicians to place the device in their pocket or wear it around their neck like a stethoscope until the next use, increasing the convenience of using ultrasound for diagnosis at the point of care.
The technology that has enabled this breakthrough revolves around their novel sensor and position sensing technology. Unlike the more orthodox approach of using multiple ultrasound transducers and complex beam forming circuitry, the Signos uses a single transducer. The user generates the image by hand movements, avoiding the need for costly, bulky, and power-hungry sensor arrays and beam-forming technology.
Pulse OximetryAnother device that has seen great strides in miniaturization is the pulse oximeter. This device is designed to measure the oxygen-carrying status of the blood and is a widely used diagnostic in hospital care. About 40% of our blood consists of red blood cells containing a substance called hemoglobin whose function is to carry oxygen around the body. A pulse oximeter measures the percentage of hemoglobin that is oxygenated (i.e., carrying oxygen). Typically, it does this by shining two wavelengths of light through the finger. By monitoring the relative absorption of these wavelengths, the saturated percentage of oxygen (SpO2) is calculated. Miniaturization in this area has been greatly aided by the availability of LEDs (light-emitting diodes) with the required wavelengths, as well as an analog microcontroller that performs all the necessary electronic control and measurement in a single chip.
Results Storage and Health RecordsAs equipment becomes miniaturized and moves out toward home use, an important consideration relates to the recording of results. For laboratory tests, this is handled easily by standard networks that can port results to the newly-emerging electronic health record framework. For home-based diagnostics, this is much more challenging.
For many tests and procedures, the resulting data can be complex in nature, such as an ECG waveform. Providing such data completely and accurately in a usable format simplifies analysis and diagnostics. The ideal is an end-to-end electronic connection through a PC networked to the computer in the clinician's office. This has been facilitated by new products such as a USB isolator (Figure 2), which provides user protection and a full USB connection. To further address the challenge, the Continua Health Alliance has been formed to define a set of standards for various diagnostics that are expected to find their way into the home, such as glucose meters, weigh scales, and blood pressure meters. The objective is to achieve interoperability of this equipment with an Application Hosting Device (AHD) that will act as a hub to port the test results to the user's software health record. This AHD could be a mobile phone, a set-top box, or a PC, for example.
The FutureThe trend toward miniaturization has now become a vital dynamic in the medical device market. The continued investment by governments around the world in healthcare academic research is creating not only new forms of diagnostics, but also increasing our understanding of biological samples and how to handle them. With this high level of research funding, coupled with increased focus on healthcare by semiconductor companies and standardization efforts such as the work of Continua, it seems clear that miniaturization is here to stay as diagnostics move from hospital to home.
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