Perfusion trend indicator

1. A perfusion trend indicator comprising:

an optical sensor that transmits multiple wavelengths of optical radiation into a tissue site, detects the optical radiation after attenuation by pulsatile blood flowing within the tissue site, and generates a sensor signal responsive to the detected optical radiation;

a patient monitor that demodulates the sensor signal so as to generate a plurality of plethysmograph channels;

a digital signal processor (DSP) within the patient monitor that inputs at least one of the plethysmograph channels and outputs a perfusion parameter accordingly;

a perfusion process that executes on the DSP so as to derive a perfusion trend from at least one of the plethysmograph channels, said perfusion trend different than historical values of said perfusion parameter, said perfusion trend responsive to trend values determined during relatively stable portions of said perfusion parameter, said trend values including at least a first baseline value during a first stable portion, a second value during a subsequent second stable portion, and a third value during a subsequent third stable portion, said perfusion trend responsive first to a first smoothed combination of said baseline and second values, and subsequently to a second smoothed combination of said second and third values, said stable portions including at least a plurality of values of said perfusion parameter; and

a patient monitor output that is responsive to the perfusion trend.

2. The perfusion trend indicator according to claim 1 wherein the perfusion process comprises:

a plethysmograph input corresponding to the at least one plethysmograph channel having plethysmograph features; and

a measure plethysmograph process that extracts a plurality of perfusion values from the plethysmograph according to the plethysmograph features.

3. The perfusion trend indicator according to claim 2 wherein the smoothing process further comprises an averaging process that generates a mean perfusion value of a set of perfusion values within a set time window.

4. The perfusion trend indicator according to claim 1 wherein the smoothing process further comprises a trim process that deletes outlying ones of the perfusion values within a time window according to predetermined criterion.

5. The perfusion trend indicator according to claim 4 wherein the patient monitor output a value representative of a sum of the first and second smoothed combinations.

6. The perfusion trend indicator according to claim 5 wherein the perfusion trend graph pops-up in a patient monitor display when the value representative of the first and second smoothed combinations after a predetermined time ΔT is less than a predetermined change in perfusion index ΔPI.

7. A perfusion trend indicator, comprising:

a sensor that transmits multiple wavelengths of optical radiation into a tissue site and that detects the optical radiation after attenuation by pulsatile blood flow within a tissue site; and

a digital signal processor (DSP) receiving as an input a plethysmograph responsive to said detected optical radiation, said DSP deriving perfusion index values responsive to said plethysmograph by generating perfusion index (PI) values from the plethysmograph according to predefined plethysmograph features and deriving a baseline PI value and PI trend values from the PI values relative to the baseline PI value, said PI trend values calculated by identifying stable data portions subsequent in time to the baseline PI value, smoothing said stable data portions and determining a difference between said smoothed stable data portions and said baseline PI; and

outputting a value representative of said difference between said smoothed stable data portions and said baseline PI value.

8. The perfusion trend indicator according to claim 7 , wherein said DSP calculates said PI trend values by identifying groups of PI values in a time window containing said stable data portions.

9. The perfusion trend indicator according to claim 8 , wherein said DSP performs said smoothing on said groups of PI values by deleting outlying values from each of the identified groups of PI values.

10. The perfusion trend indicator according to claim 9 , wherein said DSP performs said smoothing on said groups of PI values by averaging said groups of PI values.

11. The perfusion trend indicator according to claim 7 comprising a pop-up window that displays said value representing said difference between said smoothed stable data portions and said baseline PI value when said difference is less than a predetermined perfusion index ΔPI after a predetermined time ΔT.

12. The perfusion trend indicator according to claim 7 , wherein said DSP is positioned on a printed circuit board within a patient monitor.