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Photoplethysmographics using phase-division multiplexing Patent #: 5349952
ApplicationNo. 295349 filed on 08/24/1994
US Classes:600/336, Detects constituents while excluding components (e.g., noise)356/41Oximeters
ExaminersPrimary: Sykes, Angela D.
Assistant: Winakur, Eric F.
Attorney, Agent or Firm
Foreign Patent References
International ClassA61B 005/00
AbstractThe present invention provides a method and apparatus for adapting to noise sources affecting a pulse oximeter. Various available frequencies are evaluated to determine their respective noise levels and one is selected to act as the operating demultiplexer frequency. During normal operation of the pulse oximeter, the various available demultiplexer frequencies are periodically scanned to determine which has the lowest associated noise. The noise level associated with the operating frequency is used to determine the signal-to-noise ratio of the pulse oximeter signals and thereby qualify certain signals from the pulse oximeter. Those pulses associated with a signal-to-noise ratio below a predetermined threshold are rejected and excluded from use in calculating blood oxygen saturation.