US 7,315,753 B2 · Pulse oximeter with parallel saturation calculation modules

Abstract

A method and apparatus for reducing the effects of noise on a system for measuring physiological parameters, such as, for example, a pulse oximeter. The method and apparatus of the invention take into account the physical limitations on various physiological parameters being monitored when weighting and averaging a series of measurements. Varying weights are assigned different measurements, measurements are rejected, and the averaging period is adjusted according to the reliability of the measurements. Similarly, calculated values derived from analyzing the measurements are also assigned varying weights and averaged over adjustable periods. More specifically, a general class of filters such as, for example, Kalman filters, is employed in processing the measurements and calculated values. The filters use mathematical models which describe how the physiological parameters change in time, and how these parameters relate to measurement in a noisy environment. The filters adaptively modify a set of averaging weights to optimally estimate the physiological parameters.

Claims29

Dependent claims

A pulse oximeter comprising:

a sensor configured to detect first and second electromagnetic radiation signals from a patient corresponding to first and second wavelengths of light;
an analog to digital converter, coupled to the sensor, for converting the first and second electromagnetic radiation signals into first and second digital signals;
and
a processor, coupled to the analog to digital converter, the processor being programmed with
a filter module for filtering the first and second digital signals,
a normalization module configured to normalize the first and second digital signals;
a first oxygen saturation calculation module configured to determine a first oxygen saturation value using a first saturation calculation algorithm applied to the first and second digital signals,
a second oxygen saturation calculation module configured to determine a second oxygen saturation value using a second saturation calculation algorithm applied to the first and second digital signals,
a best saturation module configured to arbitrate between the first and second oxygen saturation values based on a saturation confidence associated with the first and second oxygen saturation values to select a best oxygen saturation value,
a first pulse rate calculation module configured to determine a first pulse rate from the first and second digital signals using a first pulse rate algorithm,
a second pulse rate calculation module configured to determine a second pulse rate from the first and second digital signals using a second pulse rate algorithm, and
a best rate module configured to arbitrate between the first and second pulse rates based on a pulse rate confidence associated with the first and second pulse rate signals to select a best pulse rate.

9 more elements

An apparatus for determining a patient's pulse rate using data corresponding to energy transmitted through the tissue of a patient, comprising:

a plurality of pulse rate finders configured to determine a plurality of possible pulse rates, each of the possible pulse rates having a confidence level associated therewith based on at least one quality metric;
and
an arbitrator configured to arbitrate between the plurality of possible pulse rates with regard to the confidence levels to determine the patient's pulse rate, wherein one pulse rate finder includes:
a comb filter configured to remove signal energy from the data corresponding to a fundamental frequency and harmonics thereof,
a frequency selector configured to determine a particular harmonic frequency which minimizes noise energy at an output of the comb filter, the particular harmonic frequency corresponding to the fundamental frequency, and
a pulse rate generator configured to generate the possible pulse rate corresponding to the particular harmonic frequency.

3 more elements

Dependencies are inferred from the claim text.

Pulse oximeter with parallel saturation calculation modules

Life of this patent

Pulse oximeter with parallel saturation calculation modules

Life of this patent

Abstract

Claims29