Miniaturization in Medical Equipment: Pulse Oximetry

In keeping with the trend toward miniaturization in durable medical equipment, new strides have been made recently in creating tiny versions of pulse oximeters. A pulse oximeter monitors the blood-oxygen level in a patient by displaying the percentage of hemoglobin in the bloodstream. Normal acceptable ranges are between 95 and 100 percent, but values that fall as low as 90% are still common.

As a noninvasive measurement tool, the pulse oximeter typically uses a pair of LEDs (light-emitting diodes) that face a photodiode, usually through a translucent portion of the anatomy like an earlobe or fingertip. Using both red and infrared wavelengths, a measurement of hemoglobin absorption is calculated based on the ratio of light absorption between the two. Because the signal of a pulse oximeter bounces in conjunction with the heartbeat, the detection of a pulse is essential for the monitor to function.

The miniature versions of these devices have been greatly enhanced by the availability of miniature LEDs that will function within the required wavelengths. These devices also utilize an analog microcontroller to perform all of the required measurement and electronic control within a single microchip. Miniature pulse oximeters will be useful in any situation outside of a hospital where a patient’s blood oxygenation may become unstable. They can be used in settings as diverse as mobile emergency units and pressurized aircraft’s. Essentially, no vital sign is more important than the body’s ability to absorb oxygen.

So important is the implementation of compact pulse oximeters that over half of the major international medical equipment manufacturers in China were exporting producers of these devices. One of the world’s foremost manufacturers of home-based monitors is Nonin Medical. Last year they introduced the first Bluetooth-enabled handheld device to measure pulse oximetry through the fingertips. This device, and others like it, enables doctors to remotely monitor their patient’s oxygen saturation levels through the use of a computerized home telemedicine system.

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