That woman riding the Paris subway might be turning up the volume of "Comfortably Numb" on her iPod. Or she might just be turning up electric currents flowing to her spinal cord from a medical device treating her chronic pain.

St. Jude Medical Inc. in Little Canada announced Thursday that it has gotten approval to sell a new neuromodulation device in Europe called the Invisible Trial System that is controlled with an app on an iPod Touch. Later this year, the company is planning a U.S. launch of the Invisible system, which is worn temporarily, as well as its permanent-implant version, the Proclaim.

Both stimulators send electric pulses from a pacemaker-like device into the epidural space near the spinal column to block pain signals traveling up the spine to the brain. They're controlled with signals sent via Bluetooth technology, which comes with built-in security features.

IPods and iPads are increasingly being used in health care to read data from gadgets like glucose monitors, blood-pressure cuffs and asthma inhalers. A growing number of physicians use iPads to read patient data, and last year the Mayo Clinic partnered with iPod maker Apple to launch an app that monitors health and wellness data.

Although blues and rock fans have long used music to numb their pain, St. Jude officials say their application marks the first time anyone has used an iPod to clinically manage it.

"It has a number of industry firsts: the first Bluetooth-enabled system, the first to use Apple consumer electronic products for the programming and controlling systems," Dr. Eric Fain, group president at St. Jude, said in an interview. "We're very excited about what we believe to be an important advance for spinal cord stimulation."

Treatment of chronic pain is seen as a huge commercial market. At least 1.5 billion people worldwide are affected — more than heart disease, cancer and diabetes combined, St. Jude says. Executives told investors earlier this year that they expect the market for devices to treat chronic pain in 2015 to reach $2 billion in sales, which would be growth of 8 percent for the industry niche.

"Our success in 2015 will be defined primarily by our ability to accelerate our sales growth due to three catalysts," and neuromodulation-device sales is one of them, according to a company PowerPoint presentation for investors.

The Invisible Trial System is only for temporary use by patients who are considering getting a permanently implanted system. With the Invisible, only wires are inserted in the body while the pulse generator is worn externally on the lower back. The Proclaim, a next-generation device not approved for use in any country yet, uses the same mode of action but implants the pulse generator inside the body.

Such devices are only available through a physician, in countries where regulators have approved them.

The effectiveness of spinal-cord stimulation therapy is highly variable, which is why companies like St. Jude have developed trial systems to test patients' individual responses.

Both the Invisible and the Proclaim allow patients to control the type and level of stimulation with an app on an iPod, which is provided to the patient along with the procedure. The iPod can only be used to control the medical device, which it does through secure Bluetooth technology.

Physicians, in the meantime, can use a larger iPad to program the devices and download data from them.

A spokesman for Apple said the California tech company isn't working directly with St. Jude on the systems, but rather is selling devices to the company, similar to how many hospitals and doctor's offices buy them for providers.

St. Jude settled on using iPods to replace patient interfaces on its older-generation devices in part because many people are already familiar with how they work. In theory, that should allow patients to focus more on how well the therapy works and less on the details of how it works, which has been a distraction.

"Ease of use is critical for all medical devices," Fain said. "In particular, when this type of device is being used by the patients themselves, ease of use is particularly critical in having a good experience for the patient."

Joe Carlson • 612-673-4779

Twitter: @_JoeCarlson