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Exhaustive Design Process Leads to Advance in Patient Monitoring

Originally Published MDDI July 2005 NEWSTRENDS  

Originally Published MDDI July 2005

NEWSTRENDS

Erik Swain

The Propaq LT combines features of traditional bedside monitors with portable spot-check monitoring devices.

What does it take to move a technology into a completely new paradigm? In the case of a new patient monitor from Welch Allyn (Skaneateles Falls, NY), the answer included careful attention to nursing workflow, the ability to convert military requirements into a consumer product, and perseverance when the engineering tasks looked impossible. The firm's design process could teach a thing or two to other companies hoping to come up with a potentially transformative technology.

The new technology, the Propaq LT, is the first patient monitor that combines features of traditional bedside monitors with portable spot-check monitoring devices. If adopted, it could expand continuous patient monitoring beyond acute-care settings. Making that a reality meant figuring out how to fit continuous monitoring technology into a device weighing less than 2 lb. The concept arose from a request by the U.S. military, which asked for a version of Propaq technology that medics could use on the battlefield. Specifically, it wanted to monitor heart rate, ECG, pulse oximetry, blood pressure, and respiration.

The problem, however, was that running those features on a conventional system took five circuit boards. In a device less than 2 lb, there was room for only one circuit board. Also, traditional portable monitors typically could run on battery power for 5 hours at a time, and the military needed something that could run longer.

As Welch Allyn began to work on the military's request, the company realized that if the concept worked, it might be extended to the hospital floor, where it could expand flexible monitoring. “The non-acute-care floors of a typical hospital may face an imbalance of resources versus the acute-care floors,” says Grant Gibson, Welch Allyn's director of marketing. “Thus, many of its patients go unmonitored or are only occasionally spot-checked. This product can be an ambulatory or bedside monitor, at half the cost of traditional monitors.”

Why the need for continuous monitoring? When flexible monitoring first came about, hospitals were not demanding continuous systems. But in recent years, a serious nursing shortage has changed the needs of hospitals. “Many hospitals have no way to ensure that their nurses on med-surg floors are in a position to monitor patients in the same way they did 10 years ago,” Gibson says. To enhance flexibility, the units were designed to run either as stand-alones or to be networked wirelessly to a central monitoring station.

The Propaq LT's designers fit all the electronics onto a single, 12-layer circuit board.

To address the power needs, Welch Allyn designed a self-charging cradle that in hospital settings can be connected to a bed rail. Off the cradle, the device can monitor all features for 8 hours, or two features for as long as 24 hours. The designers also subjected it to extensive ruggedness testing to meet military and emergency medicine needs.

Fitting all the electronics onto a single circuit board was tougher, and at first engineers were convinced it was impossible to condense the circuitry while still including respiration without violating IEC 60601 specifications. The answer turned up during a reverse engineering project. “I looked in the marketplace and found a competitor that had respiration and passed the certifications,” says Gibson. “So I bought it and brought it in to our engineers, who took it apart. It had a huge transformer. It was a complicated job to figure out how to take that basic technology and make it smaller and add all the power capabilities and customized features we needed. But our guys found a way to do it.” They ended up with a highly sophisticated 12-layer board.

It remains to be seen whether these efforts will pay off, but the design process appears to have taken an enormous number of factors into account, and resolved them all. Early reviews appear to be positive. “The Propaq LT is a highly versatile tool that will help caregivers become more efficient,” says Dorothy Barrow, RN, MS, manager of critical-care services at St. Charles Medical Center (Bend, OR). “We have found it very easy to operate, requiring minimal staff education time.”

Copyright ©2005 Medical Device & Diagnostic Industry

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