An improved sensor (102) for respiratory and metabolic monitoring in mobile devices, wearables, security, illumination, photography, and other devices and systems uses an optional phosphor-coated broadband white LED (103) to produce broadband light (114), which is then transmitted along with any ambient light to a target (125) such as the ear, face, or wrist of a living subject. Some of the scattered light returning from the target to detector (141) is passed through narrowband spectral filter set (155) to produce multiple detector regions, each sensitive to a different waveband wavelength range, and the detected light is spectrally analyzed to determine a measure of respiration of the subject, such as respiratory rate, volume, effort, depth, or respiratory variability. In one example, variations in components of the bloodstream over time such as hemoglobin and water are determined based on the detected light, and said measure of respiration is then determined based on the in components of the bloodstream over time, with venous compartment changes as a result of body movement and body position changes, and skin surface compartment changes as a result of sensor movement, substantially removed. In the absence of the LED light, the ambient light may be sufficient illumination for analysis. The same sensor can provide identifying features of type or status of a tissue target, such as heart rate or variability, hydration status, or even confirmation that the tissue is alive. Respiratory monitoring systems incorporating the sensor, as well as methods, are also disclosed.
