A tissue monitoring device includes a light emitter, a light detector, a probe, and a controller. The light emitter emits light through tissue in the subject, such as tissues in the subject's head. The light detector detects light emitted from the light emitter and scattered by the subject's tissue. The probe is inserted into an orifice of the subject and includes one of the light emitter and light detector. The controller communicates with the light detector and the light emitter and detects an oxygenation level of the blood in the subject's tissue based upon measurements of the scattered light. The probe may include one or more bladders for blocking ambient light and/or for ensuring contact exists between the light detector (or emitter) and an interior surface of the subject's orifice.
