A sensor for pulse oximetry or other applications utilizing
spectrophotometry may be adapted to reduce motion artifacts by fixing the
optical distance between an emitter and detector. A flexible sensor is
provided with a stiffening member to hold the emitter and detector of the
sensor in a relatively fixed position when applied to a patient. Further,
an annular or partially annular sensor is adapted to hold an emitter and
detector of the sensor in a relatively fixed position when applied to a
patient. A clip-style sensor is provided with a spacer that controls the
distance between the emitter and detector.