Physiological trend monitor

1. A physiological trend monitoring method comprising:

transmitting light having multiple wavelengths into a patient tissue site;

generating a sensor signal responsive to the light after attenuation by pulsatile arterial blood flow within the tissue site;

detecting a blood parameter trend according to the sensor signal; and

generating an alarm according to the blood parameter trend.

2. The physiological trend monitoring method according to claim 1 wherein the detecting comprises deriving a curve-fitting blood parameter measurement.

3. The physiological trend monitoring method according to claim 2 further comprising calculating a blood parameter slope from the blood parameter measurement.

4. The physiological trend monitoring method according to claim 3 wherein the alarm is responsive to a negative value of the blood parameter slope.

5. The physiological trend monitoring method according to claim 4 further comprising:

deriving a smoothed blood parameter measurement;

and setting a threshold value for the smoothed blood parameter measurement;

wherein the alarm is responsive to the smoothed blood parameter measurement crossing the threshold value.

6. A physiological trend monitor comprising:

a sensor signal responsive to multiple wavelengths of light transmitted into a tissue site and detected after attenuation by pulsatile blood flow within the tissue site;

a processor having an input responsive to the sensor signal and a physiological parameter output;

a plurality of features extracted from the physiological parameter output, wherein said features comprise statistical characteristics;

a plurality of criteria applied to the features, wherein said criteria comprise rules corresponding to said statistical characteristics; and

an alarm output generated when the criteria are satisfied.

7. The physiological trend monitor according to claim 6 further comprising:

a pattern memory that stores feature values; and

a comparator that compares the features with the stored feature values;

the criteria determining a match between the features and the stored feature values so as to trigger the alarm output.

8. The physiological trend monitor according to claim 7 wherein at least one of the features relate to the number of threshold crossings over a specified time period.

9. The physiological trend monitor according to claim 8 wherein at least one of the features relate to a duration of a threshold crossing by the physiological parameter output.

10. The physiological trend monitor according to claim 9 wherein at least one of the features relate to a trend in the physiological parameter and a slope of that trend over a specified time period.

11. A physiological trend monitor comprising:

a detector responsive to multiple wavelengths of light transmitted into a tissue site after attenuation by pulsatile blood flow within the tissue site so as to generate a sensor signal;

a processor means for calculating a physiological measurement in response to the sensor signal;

a pattern extractor means for identifying features of the physiological measurement;

a pattern memory means for storing a reference pattern; and

a pattern comparator means for triggering an alarm if the identified features match the reference pattern.

12. The physiological trend monitor according to claim 11 further comprising:

a threshold input to the pattern extractor, wherein the identified features comprise at least the number of times the physiological measurement crosses the threshold within a predetermined time period.

13. The physiological trend monitor according to claim 12 wherein the identified features comprise at least the duration of each time the physiological measurement crosses the threshold.

14. The physiological trend monitor according to claim 13 wherein the physiological measurement comprises a predictive oxygen saturation measurement.

15. The physiological trend monitor according to claim 14 further comprising a second processor means for calculating an integrator oxygen saturation measurement.