A pulse oximeter adaptively samples an input signal from a sensor in order to reduce power consumption in the absence of overriding conditions. Various sampling mechanisms may be used individually or in combination, including reducing the duty cycle of a drive current to a sensor emitter, intermittently powering-down a front-end interface to a sensor detector, or increasing the time shift between processed data blocks. Both internal parameters and output parameters may be monitored to trigger or override a reduced power consumption state. In this manner, a pulse oximeter can lower power consumption without sacrificing performance during, for example, high noise conditions or oxygen desaturations.