Systems and methods for monitoring blood pressure

1. A patient monitor configured to monitor blood pressure comprising:

a memory storing instructions for:

receiving a plethysmography signal representative of one or more patient parameters;

determining a change in a pulse shape metric of the plethysmography signal;

generating a blood pressure signal based on the plethysmography signal;

determining a change in the blood pressure signal over a period of time;

determining a confidence level of the blood pressure signal based at least in part on a correlation between the change in the blood pressure signal and the change in the pulse shape metric over the period of time, wherein the confidence level is determined to be a low confidence level based on an inverse correlation between the change in the blood pressure signal and the change in the pulse shape metric; and

in response to determining the confidence level is the low confidence level, switching from determining a blood pressure via a first monitoring mode to determining a blood pressure via a second monitoring mode different from the first monitoring mode; and

a processor configured to execute the instructions.

2. The patient monitor of claim 1 , wherein the pulse shape metric is a skew of a first derivative of the plethysmography signal.

3. The patient monitor of claim 1 , wherein the memory stores instructions for determining a high confidence level of the blood pressure signal if the blood pressure signal and the pulse shape metric change in the same direction and a difference between the change in the blood pressure signal and the change in the pulse shape metric is within a predetermined tolerance.

4. The patient monitor of claim 3 , wherein the processor is configured to instruct a display of the patient monitor to provide the blood pressure signal if a high confidence level is determined.

5. The patient monitor of claim 1 , wherein the memory stores instructions for discarding the blood pressure signal received over the period of time if the low confidence level is determined.

6. The patient monitor of claim 1 , wherein the blood pressure signal is generated based on a differential pulse transit time.

7. The patient monitor of claim 1 , comprising light drive circuitry configured to drive a respective light emitter of the plethysmography sensor to emit light into a subject's tissue to enable generation of the plethysmography signal.

8. A method for determining a confidence level of a blood pressure signal comprising:

using a processor:

receiving a blood pressure signal;

receiving a plethysmography signal;

determining a change in the blood pressure signal over a period of time;

determining a change in a pulse shape metric of the plethysmography signal over the period of time;

determining the confidence level based on whether there is an expected correlation between the change in the blood pressure signal and the change in the pulse shape metric over the period of time, wherein the confidence level is determined to be a low confidence level upon a determination that the expected correlation is not present; and

in response to determining the confidence level is the low confidence level, switching from determining a blood pressure via a first monitoring mode to determining a blood pressure via a second monitoring mode different from the first monitoring mode.

9. The method of claim 8 , wherein the pulse shape metric is a skew of a first derivative of the plethysmography signal.

10. The method of claim 8 , comprising determining a high confidence level of the blood pressure signal and providing an indication of the high confidence level on a display, in response to the expected correlation being present and a difference between the change in the blood pressure signal and the change in the pulse shape metric being within a predetermined tolerance, using the processor.

11. The method of claim 8 , comprising providing a prompt to initiate another blood pressure measurement via a speaker or a display in response to determining the confidence level is the low confidence level, using the processor.

12. The method of claim 8 , wherein determining the blood pressure via the first monitoring mode comprises determining the blood pressure based on a differential pulse transit time, and wherein determining the blood pressure via the second monitoring mode comprises determining the blood pressure based on a skew of a first derivative of the plethysmography signal.

13. A system for monitoring blood pressure comprising:

one or more plethysmography sensors configured to obtain one or more plethysmography signals;

a monitor comprising circuitry configured to:

receive the one or more plethysmography signals;

generate a blood pressure signal based on the one or more plethysmography signals;

calculate a change in the blood pressure signal over a period of time;

calculate a change in a pulse shape metric of a plethymography signal of the one or more plethysmography signals over the period of time;

compare the change in the blood pressure signal to the change in the pulse shape metric over the period of time to determine a degree of correlation;

determine a confidence level of the blood pressure signal over the period of time based at least in part on the degree of correlation, wherein the confidence level is determined to be a low confidence level based on an inverse correlation between the change in the blood pressure signal and the change in the pulse shape metric; and

in response to determining the confidence level is the low confidence level, switch from determining a blood pressure via a first monitoring mode to determining a blood pressure via a second monitoring mode different from the first monitoring mode.

14. The system of claim 13 , wherein the pulse shape metric is a skew of a first derivative of the plethysmography signal.

15. The system of claim 14 , wherein the monitor is configured to determine a high confidence level of the blood pressure signal if the blood pressure signal and the skew of the first derivative of the plethysmography signal change in the same direction and a difference between the change in the blood pressure signal and the change in the skew of the first derivative is within a predetermined tolerance range.

16. The system of claim 14 , wherein the monitor is configured to monitor blood pressure based on a scaled skew of the first derivative of the plethysmography signal in response to determining the confidence level is the low confidence level.

17. The system of claim 13 , wherein each of the one or more plethysmography sensors comprise a respective emitter configured to provide light to a subject's tissue and a respective detector configured to generate a respective plethysmography signal of the one or more plethysmography signals based on light that passed through the subject's tissue.

18. The system of claim 13 , wherein the monitor is configured to disable a blood pressure alarm in response to determining the confidence level is the low confidence level.