Parameter compensated physiological monitor

1. A monitor comprising:

a primary input from which a spectral characteristic of a tissue site is derivable;

a secondary input from which at least one parameter is determinable; and

a processor configured to output a compensated physiological measurement in response to said primary input and said secondary input utilizing a compensation relationship between said spectral characteristic and said at least one parameter and said compensated physiological measurement;

wherein said compensation relationship comprises:

baseline calibration data relating said spectral characteristic to an uncompensated physiological measurement;

modified calibration data generated from a modification of said baseline calibration data in response to said at least one parameter; and

a look-up table having sold spectral characteristic as an input and providing said compensated physiological measurement as an output according to said calibration data;

wherein said at least one parameter is a blood gas measurement and said compensation relationship further comprises:

a comparison of said uncompensated physiological measurement with said blood gas measurement;

a sensitivity control; and

modification rules responsive to said comparison and said sensitivity control, said modification rules determining said modification.

2. The monitor according to claim 1 wherein said modification rules include at least one polynomial function approximating at least a section of said baseline calibration data and adjustable so as to accommodate said blood gas measurement.

3. The monitor according to claim 2 wherein said at least one polynomial function can be represented as a Bezier curve.

4. A monitor comprising:

a primary input from which a spectral characteristic of a tissue site is derivable;

a secondary input from which at least one parameter is determinable wherein said spectral characteristic has a dependence on said parameter; and

a processor configured to output a compensated physiological measurement in response to a primary input and said secondary input utilizing a relationship between said spectral characteristic and said at least one parameter and said compensated physiological measurement;

wherein said compensation relationship comprises:

calibration data relating said spectral characteristic to an uncompensated physiological measurement;

a look-up table having at least said spectral characteristic and said at least one parameter as an input and providing said compensated measurement as an output according to said calibration data; and

wherein said at least one parameter is a carboxyhemoglobin concentration and said look up table distinguishes carboxyhemoglobin from oxyhemoglobin.

5. A monitor comprising:

a primary input from which a spectral characteristic of a tissue site is derivable;

a secondary input from which at least one parameter is determinable wherein said spectral characteristic has a dependence on said parameter; and

a processor configured to output a compensated physiological measurement in response to said primary input and said secondary input utilizing a relationship between said spectral characteristic and said at least one parameter and said compensated physiological measurement;

wherein said compensation relationship comprises:

calibration data representing a plurality of wavelength-dependent compensation calibration curves, each of said compensation calibration curves relating said spectral characteristic to said compensated physiological measurement;

a look-up table having said spectral characteristic as an input and providing as an output said compensated physiological measurement according to said compensation calibration curves; and

a wavelength determination in response to said at least one parameter so as to select a sensor wavelength and a corresponding one of said compensation calibration curves.

6. A monitoring method comprising the steps of:

inputting a sensor signal responsive to a spectral characteristic of a tissue site;

deriving a physiological measurement from said characteristic;

obtaining a parameter, wherein said physiological measurement has a dependency on said parameter;

determining a relationship between said spectral characteristic and said parameter that accounts for said dependency;

compensating said physiological measurement for said parameter utilizing said relationship; and

displaying said physiological measurement;

wherein said compensating step comprises the substeps of:

storing baseline calibration data;

modifying said baseline calibration data according to said parameter so as to provide modified calibration data; and

looking-up said physiological measurement from said modified calibration data according to said spectral characteristic; and

wherein said physiological measurement provides an SpO 2 value and said parameter is a manually input SaO 2 value, said modifying substep comprising the further steps of:

comparing said SpO 2 value to said SaO 2 value so as to determine a difference; and

determining said modified calibration data so as to reduce said difference.

7. A monitoring method comprising the steps of:

inputting a sensor signal responsive to a spectral characteristic of a tissue site;

deriving a physiological measurement from said characteristic;

obtaining a parameter, wherein said physiological measurement has a dependency on said parameter;

determining a relationship between said spectral characteristic and said parameter that accounts for said dependency;

compensating said physiological measurement for said parameter utilizing said relationship; and

displaying said physiological measurement;

wherein said compensating step comprises the substeps of:

storing baseline calibration data;

looking-up said compensated physiological measurement from said calibration data according to said spectral characteristic and said parameter; and

wherein said parameter is a hemoglobin constituent measurement and said looking-up comprises the substeps of:

distinguishing said hemoglobin constituent from oxyhemoglobin and reduced hemoglobin; and

providing an adjusted oxygen saturation measurement according to said distinguishing substep.

8. A monitoring method comprising the steps of;

inputting a sensor signal responsive to a spectral characteristic of a tissue site;

deriving a physiological measurement from said characteristic;

obtaining a parameter, wherein said physiological measurement has a dependency on said parameter;

determining a relationship between said spectral characteristic and said parameter that accounts for said dependency;

compensating said physiological measurement for said parameter utilizing said relationship;

wherein said compensating step comprises the substeps of:

storing wavelength-dependent calibration data;

determining a wavelength according to at least one of said parameter and said physiological measurement;

selecting an active portion of said calibration data according to said wavelength;

adjusting a sensor so that said spectral characteristic corresponds to said wavelength;

looking-up said physiological measurement from said active portion of said calibration data according to said spectral characteristic; and

displaying said physiological measurement.

9. The monitoring method according to claim 8 wherein said parameter is a null value and said determining substep comprises the substeps of:

identifying a range of said physiological measurement; and

specifying said wavelength according to said range.

10. The monitoring method according to claim 9 wherein said physiological measurement corresponds to oxygen saturation at said tissue site and said wavelength has a first value at normal oxygen saturation levels and a second value at below normal oxygen saturation levels.

11. A monitor comprising:

a primary input means for determining a spectral characteristic associated with a tissue site;

a secondary input means for determining a parameter that is relevant to measuring oxygen saturation at said tissue site; and

a compensation relationship means for relating said spectral characteristic, said parameter and an oxygen saturation measurement;

wherein said compensation relationship comprises a means for modifying a sensor wavelength and for selecting corresponding wavelength dependent calibration data.

12. A monitor comprising:

a primary input from which a spectral characteristic of a tissue site is derivable;

a secondary input from which at least one parameter is determinable; and

a processor configured to output a compensated physiological measurement in response to said primary input and said secondary input utilizing a relationship between said spectral characteristic and said at least one parameter and said compensated physiological measurement;

wherein said compensation relationship comprises a sensitivity control.

13. A monitoring method comprising the steps of;

receiving a sensor signal responsive to a physiological parameter of a tissue site;

deriving a physiological indication of said physiological parameter;

obtaining a parameter indication, wherein said physiological indication has a dependency on said parameter indication;

determining a relationship between said physiological indication and said parameter indication that accounts for said dependency;

determining a measurement of said physiological parameter utilizing said relationship;

wherein said relationship comprises a sensitivity control; and

displaying said measurements.