Abstract: A method and apparatus for use in pulse oximetry for discriminating between valid pulse waveforms and artifactual pulse waveforms. Systolic upstroke times for valid pulse waveforms are in a consistent, narrow range which varies only slightly from subject to subject. This narrow range, which may be defined empirically for each subject or established by a default setting applicable to all subjects, defines a predetermined range of systolic upstroke times indicative of valid pulse waveforms. The systolic upstroke time of each pulse waveform is compared against the predetermined range, and pulse waveforms are deemed valid only if their systolic upstroke times are within the predetermined range. Only arterial oxygen saturation levels based on validated pulse waveforms are accepted. The present invention may also be used to validate the heart rate and/or R-R, intervals of an ECG, and for discriminating between sleep and wakefulness in a monitored subject.

Abstract: A system for examination of a relatively small volume of biological tissue of interest using visible or infra-red radiation includes a spectrophotometer, an optical medium of a relatively large volume having selectable scattering and absorptive properties, and a processor adapted to determine a physiological property of the examined tissue. The spectrophotometer includes a light source for introducing radiation at an optical input port, a detector for detecting radiation that has migrated through a path from the input port to an optical detection port, and a processor for evaluating changes between the introduced and the detected radiation. The biological tissue of interest is positioned into the photon migration path inside the optical medium to create a tissue-medium optical path. The optical medium is adapted to limit substantially escape of photons from the tissue.

Abstract: A system for examination of biological tissue of a subject includes a light source, a light detector, a gated integrator and a integrator timing control adapted to integrate detected photons over at least two selected time intervals. The light source is adapted to introduce into the tissue, at an optical input port, pulses of electromagnetic radiation of a selected wavelength in the visible or infra-red range having duration on the order of a nanosecond or less. The detector detects, at an optical detection port, photons of modified pulses that have migrated in the tissue from the input port. The integrator and the integrator timing control register all photons arriving at the detector port over preselected time intervals of the arrival time of the modified pulses. The time-dependent shape of the modified pulses reflects the scattering and absorptive properties of the examined tissue.

Abstract: A phase modulated spectroscopy (PMS) system for detecting a pathophysiological condition in a subject includes two laser diodes emitting radiation at wavelengths of about 754-760 nm and 816-840 nm. These two laser diodes are modulated sinusoidally at about 220 MHz. The signals from each laser diode are brought to the subject by a bifurcated plastic optical fiber of 1 mm diameter. After transmission through the subject, the signals are detected by a Hamamatsu R928 photomultiplier (PMT), which generates two experimental signals. The experimental signals are compared to a reference signal in a phase detector. The respective phase shifts experienced by the signals are combined to form sum and difference signals, which are correlated to a pathophysiological condition.

Abstract: Methods and apparatus using the principles of time-resolved spectroscopy are disclosed. The present invention employs incident light pulses of sufficiently short duration to permit the rate of the rise and decay of such pulses to be measured. Consequently, the rate of decay, u, permits a determination of the concentration of an absorptive pigment, such as hemoglobin. The present invention also allows the precise path length the photons travel to be determined. Using this path length information and by measuring changes in optical density using known continuous light (CW) spectrophotometry systems, the methods and apparatus disclosed allow changes in the concentration of an absorptive pigment to be correctly be measured. From these data, the oxygenation state of a tissue region, such as the brain, can be accurately determined in real time.

Abstract: A sensitive photon detector can be used for external detection in vivo of emission from a body organ, for instance of singlet oxygen emission in the near infrared at 1280 nm, for various purposes such as control of oxygenation of a patient. At such a wavelength bone and overlying tissue are sufficiently transparent to allow detection exteriorly of the body. Stray light and thermal emissions at this wavelength in a lit room are sufficiently low, or can otherwise be controlled, to allow detection of this singlet radiation by for instance a cooled Ge detector, to determine a rate of detected photons. Detection of this radiation can be taken for instance as indicating damage in process from over-oxygenation of a patient, allowing preventing and remedial measures to be taken in oxygen treatment.