Masimo's SHARC®-based Portable Oximeter Accurately Measures Blood Carbon Monoxide

Every winter, people rush into emergency rooms complaining of flu-like symptoms such as fatigue, headache, dizziness, drowsiness, and nausea, while others come in with shortness of breath or chest pain that could suggest a heart attack. These patients could be victims of carbon monoxide (CO) exposure. CO is harmful when inhaled as the odorless gas decreases the oxygen carrying capacity of the blood, thereby reducing the amount of oxygen delivered to the tissues and vital organs. CO poisoning, often the result of faulty home-heating systems, can be very difficult to diagnose unless the patient has been exposed to an obvious source such as a fire or car exhaust.

In the past, methods for measuring CO poisoning have been limited to invasive bloods tests that are analyzed by blood gas machines that feature CO-Oximetry measurement ability. But these machines are usually found only in large hospitals, and when CO poisoning is a possibility, lives are at stake and time is short, so quick, non-invasive measurement methods are far more desirable. Often, it's first responders such as emergency department workers, EMS clinicians, or firefighters who need diagnostic information to expedite treatment decisions.

To that end, Masimo Corporation developed the Rainbow SET Rad-57 Pulse CO-Oximeter™, a device that accurately measures CO in the blood. The Rad-57 is based on the company's Signal Extraction Technology (SET)®, a method for acquiring, processing, and reporting arterial oxygen saturation and pulse rate that combines proprietary signal processing algorithms with innovative sensor technologies. The signal-processing engine driving the device is none other than a code-protected ROM SHARC® processor from Analog Devices, Inc. (ADI), selected specifically for its floating-point math capabilities, which provide the precision and accuracy required by Masimo's life-critical algorithms.

How It Works
A privately held medical technology company, Masimo develops, licenses, and markets advanced medical signal-processing technologies and products that monitor patient vital signs non-invasively. Masimo SET Pulse Oximetry has established itself as the "Gold Standard" in the pulse oximetry industry due to an unsurpassed ability to perform accurately when other technologies fail, such as during patient motion or low perfusion.

Designed for portability, the Masimo Rainbow SET Rad-57 Pulse CO-Oximeter is a small, handheld device that comprises a SHARC signal processor, proprietary signal-processing algorithms, innovative sensor technologies, and a user interface consisting of a display, clip, and keypad.

Here's how the typical pulse oximeter process works: a technician places a clip onto a patient's finger, or foot in the case of infants and neonates. The unit's sensors generate light at two wavelengths. The processor can compute the proportion of hemoglobin (Hb) that is oxygenated by calculating the absorption at the two wavelengths. The device shows the percentage of Hb that is saturated with oxygen and produces an audible signal for each pulse beat, a heart rate, and a graphical display of the blood flow.

"SHARC is helping Masimo's proprietary math-intensive algorithms save lives by making diagnostic tools...highly portable and available in a moment's notice."

The Masimo Rainbow SET Rad-57 Pulse CO-Oximeter advances conventional pulse oximeters technology in several ways. First, it incorporates Masimo SET, which involves multiple complex algorithms, sometimes working in parallel. Masimo SET also includes sensor designs that minimize noise and improve the identification of the desired physiological signal. Masimo Rainbow SET technology utilizes further breakthroughs in system theory mathematics and adaptive signal processing algorithms. It employs sophisticated new sensor technology with eight distinct wavelengths (not just two). The result is a rich stream of physiological data that accurately measures CO in the blood non-invasively in seconds.

No Math Anxiety
The SHARC processor supports 32-/40-bit floating-point operations, featuring ADI's Super Harvard Architecture, with a large on-chip SRAM, and an independent DMA engine with multiple internal busses to eliminate I/O bottlenecks. The processor contains two computational processing elements that operate as a Single-Instruction, Multiple-Data (SIMD) engine, which is efficient at executing math intensive signal-processing algorithms.

The SIMD architecture enables Masimo to execute its numerous math-intensive algorithms in a much shorter period of time. This means that the processor can spend more time in a low-power mode, which decreases power consumption and increases operating time up to 8 hours using four "AA" batteries.

The SHARC processor integrates numerous on-chip features, such as on-chip mask-programmable non-volatile ROM (4M bit), including code-protection. Other integrated on-chip features of the SHARC include: two data address generators (DAG1, DAG2), a program sequencer with instruction cache, PM and DM busses capable of supporting four 32-bit data transfers between memory and the core at every core processor cycle, three programmable interval timers with PWM generation PWM capture/pulse width measurement, and external event counter capabilities, on-chip SRAM (3M bit), an 8- or 16-bit parallel port that supports interfaces to off-chip memory peripherals, and a JTAG test access port (TAP).

Masimo capitalized on many of the integrated peripherals/interfaces of the SHARC processor. For example, Masimo incorporated the synchronous serial ports into the CO-Oximeter unit's signal chain. The serial ports provide an inexpensive interface to a wide variety of mixed-signal peripheral devices such as ADI's analog-to-digital converters (ADCs) and digital-to-analog converters (DACs), which Masimo uses in the CO-Oximeter. The SHARC processor features six synchronous serial ports, made up of two data lines, clock and frame sync. The data lines can be programmed to either transmit or receive, and each data line has a dedicated direct memory access (DMA) channel.

The SHARC processor's pair of serial peripheral interface ports (SPIs), industry-standard synchronous serial links that enable the processor to communicate with other SPI-compatible devices, are also part of the CO-Oximeter signal chain. The SHARC processor also features a DMA controller and a digital audio interface (DAI), with its own unique set of attributes.

Tools Speed Time to Market
Masimo leveraged ADI's VisualDSP++ project management environment, which let programmers develop and debug an application. The environment includes an easy-to-use assembly language, which is based on an algebraic syntax, an archiver (librarian/library builder), a linker, a loader, a simulator, a C/C++ compiler, and a C/C++ run-time library that includes mathematical functions. The tools improve code efficiency, and the compiler was developed for efficient translation of C/C++ code to assembly.

ADI provides a range of evaluation platforms for customers to use as a cost-effective method to learn more about developing or prototyping applications with its processors, platforms, and software tools. Each platform comprises an evaluation board and a suite of VisualDSP++ software, sample application programs, a power supply and a USB cable. ADI was able to provide Masimo an early development platform that contained a non-code protected SHARC processor so the company could get an early start on code development.

Masimo also used ADI's in-circuit emulator, which provides high-performance code download and debugging, enabling applications to be tested very quickly. ADI emulators are tools that every developer needs to test and debug hardware and software systems. They are used with the JTAG test access port (TAP) on the SHARC processor. The emulator uses the TAP to access the internal features of the processor, which allowed Masimo's developers to load code, set breakpoints, observe variables and memory, and examine registers.

This ROM-protected SHARC processor is source-code compatible with other SHARC processors in the family, so Masimo did not have to rewrite code – everything Masimo had written for previous applications ran on the new processor, which helped save money and speed time to market.

Thanks to advances in medical technology and great development tools, SHARC is helping Masimo's proprietary math-intensive algorithms save lives by making diagnostic tools once consigned to hospitals highly portable and available in a moment's notice.

Masimo, SET, and Signal Extraction Technology are registered trademarks of Masimo Corporation, and Rad-57 is a trademark of Masimo Corporation. Rainbow and Pulse CO-Oximeter are trademarks of Masimo Labs.

For more information about Masimo Corporation, visit their Web site at

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