Masimo is setting a brisk pace in pulse oximetry market

Masimo is setting a brisk pace in pulse oximetry market – Masimo Corp

The pulse oximetry segment has been one of the fastest-growing parts of the patient monitoring market over the last five years, catapulting Nellcor Puritan Bennett (Pleasanton, California) to a prominent position in the industry, and contributing significantly to the growth of Nonin (Plymouth, Minnesota), and Novametrix (Wallingford, Connecticut). Yet there is a growing consensus that pulse oximetry has proven to be a fair-weather friend to clinicians seeking to manage difficult patients. During patient transport, motion artifact has been a consistent problem. In surgical and emergency department settings, for patients in seizures, or experiencing electro-surgery, pulse oximetry has exhibited noise interference.

For many patients with significant desaturations or low peripheral perfusion, today’s generation of oximetry, whether from Nellcor, Novametrix, Nonin, or other OEM suppliers, has not proven to be an ideal solution – causing pulse oximetry to become an unreliable indicator at the very time accurate data is most needed. Nonetheless, in spite of those limitations in some applications, pulse oximetry has become a standard of care, particularly in the operating room, in post-anesthesia recovery, surgical and other ICUs and in the emergency department.

As with other technologies, pulse oximetry started as a stand-alone device, but broadened to become a module in high-end patient monitoring systems, and one of the standard group of parameters included in all configured, portable and line-operated patient monitors. As the technology became cheap enough, it appeared in hand-held devices, some costing as little as $1,000. The growth and popularity of this parameter has spurred the growth of several companies, but none more than Nellcor, the recognized market leader, which says it has licensed its technology to 40 medical equipment suppliers worldwide.

Because of the key role pulse oximetry plays, and the desire to expand it to new applications, much research has been done on improving its underlying infrared sensor and detection technology, and making it a more reliable, non-invasive measurement. Nellcor took a big step by correlating the ECG waveform with the oximetry pulse, a feature it patented as C-Lock. However, in spite of all the research done by the companies that are significant OEM suppliers to the medical equipment market, none (including C-Lock) seemed to achieve more than modest improvements in the reliability of non-invasive oximetry measurement for patients with low perfusion or when the measurement is made in tremor or high motion artifact situations.

Until now.

Sometimes it takes someone who is outside of the forest to see the path through the woods that all those lost inside have been searching for. That seems to have been the case in oximetry. Masimo Corp. (Mission Viejo, California) recently patented new sensor and detection technology in pulse oximetry that solves the core problems. Masimo’s solution to overcoming oximetry’s problems is to use two signals, one in the red and one in the infrared spectrum. It then combines those two signals, isolating the noise signal, which it then uses to remove the noise from the infrared pulse oximetry signal. That improves measurement sensitivity and accuracy (signal to noise ratio), even for low amplitude signals. Masimo patented the signal extraction technology (SET), and has been validating it in clinical trials conducted over the last two years at various worldwide sites.

Improving, extending oximetry applications

Masimo’s improvement of the technology has already been noted by companies trying to improve oximetry measurement accuracy, and to extend oximetry into new applications to open up new market segments. The first to sign on was Baxter (Deerfield, Illinois), which will use the technology in its new products. Next, Kontron Instruments Ltd. (Watford, United Kingdom) switched to it, bringing the new technology to Europe. Several other companies are evaluating the SET technology for other measurement applications. BBI has learned that Healthdyne Technologies (Marietta, Georgia) will be evaluating the Masimo technology to bring oximetry monitoring to the fetus during delivery, an application fraught with artifact interference that has challenged the best traditional pulse oximetry systems.

The first part of Masimo’s technology breakthrough is in the basic design of the IR finger sensors. By moving the optical sensors back from the skin to stabilize the IR path through the tissue, even when the extremity is in motion, the Masimo finger sensors alone provide a significant improvement even using the conventional IR processing technology. Illustrating that improvement (Table 2 on page 68) is data provided by Steven J. Barker, PhD, MD, professor and head of the Department of Anesthesiology at the University of Arizona (Tucson).

During that intentionally introduced motion artifact, there is no real change in oxygen saturation; however, because of the IR sensors sensitivity to such artifact, there is a false indication of change in saturation. The magnitude of that change is substantially less with the Masimo sensor than with a conventional sensor. The conventional sensor shows a false drop to almost 85% saturation, enough to indicate a serious patient desaturation, or to generate annoying false alarms in the operating room setting. Those false indications motivate some clinicians to disable alarms, placing the patient at risk if a real desaturation occurs and happens to go unnoticed by a busy anesthesiologist.

Note that the Masimo sensor never drops more than 2% to 3%, not a large enough desaturation to be medically significant, or trigger false alarms. The improvement with that sensor technology alone means that the clinician will be treating the patient monitored with a Masimo sensor, not the motion artifact.

Processing the pulse oximetry signal

The second improvement by Masimo has to do with the methodology used to process the pulse oximetry signal. In conventional pulse oximetry, the available IR signal contains both oximetry data and noise, and until now there has been no highly reliable means to identify and isolate the noise component so it can be removed, leaving just the oximetry signal. The new signal extraction technology developed by Masimo solves that problem by isolating the noise signal, and then removing it to obtain the true oximetry signal that tracks the patient’s blood oxygen saturation.

The improvement provided by that development is illustrated by the data in Table 2 and Table 3 on page 69, again provided by Barker. In those tests, a Masimo system with SET technology was compared to processing from two popular, and widely deployed, Nellcor oximeters – the older N-200 and the newer N-3000, which Nellcor indicates was designed to identify and reject artifact caused by patient movement.

For the purposes of the test, a tapping or a rubbing motion artifact, typical of that encountered in patient transport, tremor, and other routine monitoring situations, is introduced on one of the patient’s hands which has the Masimo sensor and the Nellcor sensors. The other hand, which does not experience the artifact, has a Nellcor sensor providing the reference signal (unaffected by artifact).

In Table 3 on page 69, the top tracing of the N-3000 initially tracks the actual desaturation down to a value of 80% and then freezes its display at the onset of the motion artifact, and continues to remain frozen at the 80% value for another minute, when it then drops to 0% saturation. During the same time, the actual patient desaturation continues down to a value of 65% saturation and quickly resaturates to above 90% saturation.

While the Nellcor unit is still falsely indicating 0%, there are two small additional desaturations to about 90% saturation, which that unit misses. The Nellcor appears to recover only after the rubbing motion artifact is removed, at which time it quickly jumps back to track the patient.

Conversely, the Masimo system accurately tracks the desaturation to 65% (overshooting a bit), and then tracks the resaturation (with a slight delay), sees and tracks the second brief desaturation starting at minute 46 during the rubbing artifact, and continues to accurately reflect the saturation when the rubbing artifact ceases.

Suppose in the clinical setting that the actual motion artifact had occurred a bit earlier, and the N-3000 had again frozen when the artifact began, at a normal saturation value. When the desaturation occurred, it presumably could have been missed, and the patient might have gone untreated.

In Table 4, comparing the N-200 against the Masimo system, the N-200 begins falsely to desaturate almost immediately after the tapping motion occurs, over a minute earlier than when the real desaturation begins (around minute 58). It reaches the wrong end point almost a minute before the minimum of the real desaturation, and then appears to indicate a second desaturation around minute 60, which never occurs. The N-200 seems to provide inconsistent and inaccurate data during the entire tapping motion artifact.

Conversely, the Masimo unit tracks the desaturation very precisely, indicates the correct end point (around 70% saturation), and tracks the resaturation very well.

Research data supports SET

These are but two examples seen in a continuing stream of research data that seems to provide compelling evidence in support of the improvement Masimo has made in overcoming the high false positive alarms and providing accurate saturation data even in the presence of substantial motion artifacts. Such improved performance by the Masimo OEM board and sensors is one reason that patient monitoring companies are gravitating toward the SET technology.

Masimo’s SET technology should boost a healthy segment of the industry to increase its growth rate even more by expanding oximetry into new applications. Unit sales of pulse oximeters had grown over the last five years from 35,000 units a year in 1991 to more than 75,000 units a year in 1995, so the total installed base of pulse oximetry at the end of 1995 exceeded 325,000 units for current market leader Nellcor.

The availability of the improved Masimo ET technology may open up the fetal oximetry market, and improve the transport and neonatal monitoring market, which will enhance oximetry sales a bit.

Apart from the improved technology, there is another reason why a change in market alignment may come quickly. Masimo is sharing the financial benefits of its sensor sales with its patient monitoring partners. By providing improved margins on sensor sales in comparison with competitors, medical suppliers offering Masimo sensors augment their disposable revenues substantially compared to selling other sensors. In a time of reduced capital equipment revenues due to managed care, increased margins on disposables can be an important ingredient in the financial success of many suppliers.

While the exact reordering and timing of the OEM suppliers’ reshuffling in the industry remains to be seen, it is clear that Masimo’s SET technology is establishing a new “gold standard” for pulse oximetry and accuracy that will improve and extend the reach of non-invasive oximetry measurements across the patient monitoring industry worldwide.

COPYRIGHT 1996 A Thomson Healthcare Company

COPYRIGHT 2004 Gale Group