System and method for measuring blood pressure

1 . A method, comprising:

measuring a first blood pressure,

the measuring of the first blood pressure comprising:

varying a cuff pressure of a cuff on an appendage of a subject and coupled to a controller configured to control the cuff pressure;

generating a speckleplethysmography signal from a speckleplethysmography sensor on the appendage and coupled to the controller, the speckleplethysmography sensor comprising a coherent light source, configured to illuminate tissue of the subject, and an image sensor configured to receive light from the tissue; and

determining the first blood pressure based on the speckleplethysmography signal and based on the cuff pressure,

wherein:

the first blood pressure is a systolic blood pressure, and

the determining of the first blood pressure comprises:

decreasing the cuff pressure; and

determining the cuff pressure at a point in time, while the cuff pressure is decreasing, at which a measure of blood flow, based on the speckleplethysmography signal, indicates an increase in blood flow, and

wherein the measure of blood flow is based on a method of pulse detection, comprising:

calculating a measure of quality of a candidate pulse; and

determining whether the candidate pulse is part of a sequence of pulses.

2 . The method of claim 1 , wherein the determining of whether the candidate pulse is part of a sequence of pulses comprises:

determining whether an amplitude of the candidate pulse is consistent with an amplitude trend within the sequence of pulses, and

determining whether a position in time of the candidate pulse is consistent with positions in time of the sequence of pulses.

3 . The method of claim 1 , wherein the speckleplethysmography signal is low-pass filtered, and the measure of blood flow is based on the low-pass filtered speckleplethysmography signal.

4 . A method, comprising:

measuring a first blood pressure,

the measuring of the first blood pressure comprising:

varying a cuff pressure of a cuff on an appendage of a subject and coupled to a controller configured to control the cuff pressure;

generating a speckleplethysmography signal from a speckleplethysmography sensor on the appendage and coupled to the controller, the speckleplethysmography sensor comprising a coherent light source, configured to illuminate tissue of the subject, and an image sensor configured to receive light from the tissue; and

determining the first blood pressure based on the speckleplethysmography signal and based on the cuff pressure,

wherein:

the first blood pressure is a diastolic blood pressure, and

the determining of the first blood pressure comprises:

decreasing the cuff pressure; and

determining the cuff pressure at a point in time, while the cuff pressure is decreasing, at which the speckleplethysmography signal has a maximum amplitude.

5 . A method, comprising:

measuring a first blood pressure,

the measuring of the first blood pressure comprising:

varying a cuff pressure of a cuff on an appendage of a subject and coupled to a controller configured to control the cuff pressure;

generating a speckleplethysmography signal from a speckleplethysmography sensor on the appendage and coupled to the controller, the speckleplethysmography sensor comprising a coherent light source, configured to illuminate tissue of the subject, and an image sensor configured to receive light from the tissue; and

determining the first blood pressure based on the speckleplethysmography signal and based on the cuff pressure,

wherein:

the first blood pressure is a diastolic blood pressure, and

the determining of the first blood pressure comprises:

decreasing the cuff pressure; and

determining the cuff pressure at a point in time, while the cuff pressure is decreasing, at which a discrepancy between the speckleplethysmography signal and a template waveform is less than a threshold.

6 . A method, comprising:

measuring a first blood pressure,

the measuring of the first blood pressure comprising:

varying a cuff pressure of a cuff on an appendage of a subject and coupled to a controller configured to control the cuff pressure;

generating a speckleplethysmography signal from a speckleplethysmography sensor on the appendage and coupled to the controller, the speckleplethysmography sensor comprising a coherent light source, configured to illuminate tissue of the subject, and an image sensor configured to receive light from the tissue; and

determining the first blood pressure based on the speckleplethysmography signal and based on the cuff pressure,

wherein:

the first blood pressure is a diastolic blood pressure, and

the determining of the first blood pressure comprises:

decreasing the cuff pressure; and

determining the cuff pressure at a point in time, while the cuff pressure is decreasing, at which a low-frequency speckleplethysmography signal ceases to increase.