Abstract: Apparatus for the in-vivo measurement of blood oxygen levels in a patient, includingan elongate probe adapted to pass into the oesophagus of the patient,a fibre optic light channel for illuminating the internal surface of the oesophagusa photosensor for monitoring light reflected from the internal surface of the oesophagusand a signal processor for determining from the reflected light signal the degree of oxygenation of blood in the internal surface of the oesophagus.A single optical fibre light channel may be utilized both to conduct light into the probe to illuminate the internal surface of the oesophagus, and to conduct light reflected from the internal surface of the oesophagus to the exterior of the patient.

Abstract: An apparatus for monitoring patient functions, particularly depth of anesthesia includes an oesophageal probe having a balloon located in the patient's oesophagus to provoke contractions thereof; a gas cylinder or pump for applying air or saline solution to the balloon and a sensor for detecting signals indicative of oesophageal contraction, from which signals the depth of anesthesia may be estimated.

Abstract: A method of monitoring the depth of anaesthesia of a patient, comprising stimulating contractions in the oesophagus of the patient, for example using an inflatable oesophageal balloon, obtaining signals indicative of the oesophageal contractions using a sensor, and deriving from the signals an output indicative of the rate of occurrence of signals having a magnitude greater than a preset threshold value, and apparatus for carrying out the method.An alternative aspect comprises assigning a score value to each of a plurality of different bodily functions of a patient, for example heart rate, blood pressure, degree of sweating, and formation of tears, the said score values being indicative of a depth of anaesthesia or sedation, summing the score values, and producing an output from the summed score values indicative of the amount of anaesthetic to be fed to the patient.