Embodiments of the present disclosure include a handheld multi-parameter patient monitor capable of determining multiple physiological parameters from the output of a light sensitive detector capable of detecting light attenuated by body tissue. For example, in an embodiment, the monitor is capable of advantageously and accurately displaying one or more of pulse rate, plethysmograph data, perfusion quality, signal confidence, and values of blood constituents in body tissue, including for example, arterial carbon monoxide saturation (“HbCO”), methemoglobin saturation (“HbMet”), total hemoglobin (“Hbt”), arterial oxygen saturation (“SpO2”), fractional arterial oxygen saturation (“SpaO2”), or the like. The monitor can determine which a plurality of light emitting sources and which of a plurality of parameters to measure based on the signal quality and resources available.