Medtronic Inc.’s (NYSE:MDT) headache over its Physio-Control Inc. subsidiary is turning into a veritable migraine, as it reveals another issue with its LifePak line of defibrillators.

Redmond, Wash.-based Physio-Control said it issued a "field correction" for some of its LifePak 20/20e defibrillators, after discovering that some of the devices might lose battery power while in operation.

The device’s primary power source is wall power, but in cases where the battery fails and no wall outlets are available, the problem "could delay the delivery of defibrillation therapy, which could potentially result in serious injury or death" in devices manufactured before Jan. 9, 2009, according to a press release. Physio-Control said there have been reports of failures during patient use over the eight years the product’s been on the market and one, unconfirmed, "adverse patient event."

The company is notifying all affected customers by certified mail and plans to offer free updates with on-site field service visits. To figure out if a LifePak 20/20e is defective, customers can visit www.physio-control-notices.com/LP20Power.

It’s not the first problem for the LifePak line this year. In April, just a few months after the Food & Drug Administration cleared Physio-Control to resume defibrillator sales, the FDA issued a Class I recall of the LifePak 15 product. And last September, the FDA made the pull-back of its LifePak CR defibrillator a Class I recall. A Class I recall means the federal watchdog agency believes a device can cause “serious adverse health consequences or death.”