The present invention is a method and system for providing auxiliary power to an integrated anesthesia delivery and patient monitoring system. When AC main power is unavailable or inadequate to power a patient monitoring device of the integrated system, DC power from a battery in an anesthesia machine of the integrated system provides power to the patient monitoring device through a DC power connection. Distribution of the battery power is controlled by a first, normally closed solid state switch in the anesthesia machine and a second, normally open solid state switch in the patient monitoring device. The battery is also configured to provide DC power to the anesthesia machine when AC mains power is unavailable to the anesthesia machine. The method and system utilizes required DC auxiliary power from the anesthesia machine to provide DC auxiliary power to the other devices.