The optional PS500 Power Supply Unit used with the Evita V500 and Babylog VN500 ventilators is defective and is being recalled by Dräger. The defective device may not indicate a low battery charge until the battery is totally depleted. When the battery is depleted, mechanical ventilation will stop and manual ventilation will be required until the device is connected to the main power. The company investigated the defective product after it received complaints that found that the batteries installed in the PS500 depleted much earlier than expected, although the battery indicator showed a significantly charged battery. No patient injuries have been reported so far.