Mountain View, CA —Two factors determine the success of medical product design. The product has to be easy to use and maintain, and it has to work. "If it isn't easy to use, how well it works is irrelevant," says Robert Stone, director of Pacific Consultants' Medical Group, who holds a number of patents for medical products.
He and Pacific Consultants—a multi-specialty product development organization— have a patent pending for a new, portable, wireless device with inexpensive flexible circuitry that detects ECG information and transmits the signal to a pulse oximeter to provide accurate blood oxygenation information.
The medical community uses pulse oximeters—sensing devices placed on a patient's finger or toe and connected to a computer—to provide optical data showing each heart beat, and by extension, blood flow. Because the duration of each heart contraction is predictable, the device can provide information about arterial blood flow (i.e., oxygenated blood)—as long as the patient doesn't move. "Noise" generated by movement, however, makes it very hard to isolate information about arterial blood flow.
Non-invasive, continuous ventilation monitoring is now possible with an ECG electrode and wireless bio-telemetry device embedded in a flexible circuit placed on a patient's chest, and a ventilation sensor attached to the patient's abdomen and connected to a pulse oximeter. A computer monitor would display the heart rate and respiration results provided by these linked devices.
"The best way to measure oxygenation of the blood is to link pulse oximetry with ECG," Stone says. Unfortunately, doing so with conventional equipment creates additional work for nursing and technical staff, and hospital personnel consistently have rejected suggestions to link the two systems together.
The new device offers an easier way to get the information. It features a flexible circuit with an embedded electrode and telemetry system (including an antenna). This circuit attaches to the patient's chest with hydrogel adhesive, making it possible to remove the device painlessly. The heart rate information goes to the same computer that receives input from a hydrogel-adhered ventilation sensor placed at the patient's thorax or abdomen and connected to the pulse oximeter.
"The single flex circuit can be produced by automated processes, resulting in low manufacturing costs," says Stone. "A single-use version will cost around $10-20 per application, which is about normal for the U.S. disposables market. The device is what we call 're-sposible'—in that for non-sterile applications such as home monitoring, it can be cleaned and reused several times. In such applications, the cost would drop to a quarter of the disposable cost." It will be manufactured by a medical equipment company using Pacific Consultants' intellectual property, and should be available later in 2001.
Some people—such as premature babies, and those with emphysema, congestive heart failure, and spinal injuries that compromise breathing—need continuous ventilation monitoring. It would also be useful to be able to monitor ventilation of airplane pilots, in the event of unexpected depressurization. "With non-invasive continuous monitoring of ventilation, Payne Stewart and his passengers would not have died," Stone says. "He'd have had early warning that the plane was depressurizing, and could either have used oxygen or taken the plane low enough to survive."
Specifics of the bio-telemetry system have not yet been finalized, but three different approaches can be used. "We can use a classic 5-kHz inductive coupling, similar to those used to measure fitness, or build a 900-Hz FM medical telemetry system, or even embed a Bluetooth chip," says Stone. "All of these will work."
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