Accurate continuous blood pressure measurement device

1 . A continuous blood pressure measurement device for measuring arterial blood pressure, comprising:

a cuff that is configured to fit on a blood pressure measurement site to compress an artery of the measurement site;

an inflation/deflation unit that consists of a piezoelectric pump and a valve, to increase and decrease a pressure inside the cuff;

a pressure detection unit that is configured to detect a cuff pressure, which is the pressure inside the cuff;

at least one light-emitting diode and at least one photodiode, wherein at least one pair of the light-emitting diode and the photodiode is configured to generate photoplethysmogram;

a volume detection unit that is configured to detect an arterial volume signal indicating a volume of the artery per unit length;

a control unit that is configured to set the cuff pressure by controlling the inflation/deflation unit, wherein the control unit comprises a model-based predictive controller to output digital to analog converter (DAC) signals to both pump and valve simultaneously, wherein the model-based predictive controller comprises a system model and a two-degree-of-freedom (2DOF) proportional-integral-derivative (PID) controller, wherein the system model incorporates arterial mechanical properties and cuff plant electromechanical properties, and wherein a global gain adjustment is used to prevent system vibration and improve performance;

and an extraction unit that is configured to measure volume and blood pressure waveforms to detect systolic with systolic timing, diastolic with diastolic timing, and mean arterial pressure (MAP) of a subject, wherein a bilinear transformation is used for error correction, wherein a volume setpoint corresponds to the cuff pressure below the mean arterial pressure to prevent skin discoloration, wherein the extraction unit is further configured to construct a true blood pressure waveform using a lower cuff pressure to improve subject comfort.

2 . The continuous blood pressure measurement device of claim 1 , wherein the cuff is applicable to the measurement site, wherein the measurement site includes at least one of the subjects' fingers, wrists, or ankles, where the wrists and ankles are preferred measurement sites for infants and thumbs are for other age groups.

3 . The continuous blood pressure measurement device of claim 1 , wherein the valve comprises at least one of a piezoelectric valve, a solenoid valve, an electromechanical valve, or a fixed orifice, which is configured to release pneumatic pressure in a cuff airbag and wherein pneumatic pressure is modulated by the pump.

4 . The continuous blood pressure measurement device of claim 1 , wherein the volume detection unit, the control unit, and the extraction unit operate in a CPU of a microcontroller, wherein input channels of the microcontroller comprises of digital input channels and/or analog to digital converter (ADC) input channels, and whose output channels of comprises analog output channels and/or digital to analog converter (DAC) and/or Pulse Width Modulation (PWM) output channels, hereinafter referred to as the DAC.

5 . A control method of controlling a continuous blood pressure measurement device for measuring blood pressure, the method comprising:

providing a cuff that is configured to fit on a blood pressure measurement site to compress an artery of the measurement site;

increasing and decreasing a pressure inside the cuff using an inflation/deflation unit that consists of a piezoelectric pump and a valve;

detecting a cuff pressure using a pressure detection unit, which is the pressure inside the cuff;

generating photoplethysmogram using at least one light-emitting diode and at least one photodiode;

detecting an arterial volume signal indicating a volume of the artery per unit length using a volume detection unit;

setting the cuff pressure by controlling the inflation/deflation unit using a control unit, wherein a model-based predictive controller comprises a system model and a 2DOF PID controller, wherein the system model incorporates arterial mechanical properties and cuff plant electromechanical properties, wherein a global gain adjustment is used to prevent system vibration and improve performance;

and measuring volume waveform and blood pressure waveform to detect systolic with systolic timing, diastolic with diastolic timing, and MAP of a subject using an extraction unit, wherein a bilinear transformation is used for error correction, wherein a volume setpoint corresponds to the cuff pressure below the mean arterial pressure to prevent skin discoloration, wherein the extraction unit is further configured to construct a true blood pressure waveform using a lower cuff pressure to improve subject comfort.

6 . The control method of claim 5 , wherein the system model describes nonlinear, hysteretic, and time delay system behaviors for the arterial mechanical properties and the cuff plant electromechanical properties, wherein the cuff plant properties consist of cuff airbag mechanical properties, pump electromechanical properties and valve electromechanical properties, wherein the arterial mechanical properties and the cuff plant properties are arranged sequentially and connected by an arterial pressure.

7 . The system model of claim 6 , wherein the arterial mechanical properties describe a relationship between the arterial volume and a transmural pressure, wherein the arterial mechanical properties outputs to the arterial pressure using the arterial volume and cuff pressure as the input.

8 . The system model of claim 6 , wherein the cuff plant electromechanical properties use the arterial pressure outputted from the arterial mechanical properties as the input and derives a pump DAC and a valve DAC from cuff airbag mechanical properties, pump electromechanical properties and valve electromechanical properties, wherein the cuff airbag mechanical properties can be in a form of mathematical formular or as a payload to the pump and valve, wherein the pump DAC and the valve DAC are the output of the system model for the control method.

9 . The control method of claim 5 , wherein the 2DOF PID controller provides the pump DAC and valve DAC to compensate the model-based predictive controllers for errors not being modeled such as the artery mechanical property changes with time, wherein the linear characterization of the 2DOF PID allows a fast control system response.

10 . The control method of claim 5 , wherein the inputs of the 2DOF PID controller include the volume error, the cuff pressure, and the pump and valve DAC values in the previous steps as the inputs, wherein the output of the 2DOF PID controller include the pump DAC and the valve DAC, which are generated simultaneously.

11 . The control method of claim 5 , wherein the pump and the valve are correlated in such a way that the valve closes as much as possible, so that an output of the pump is minimized to reduce its power usage.

12 . The control method of claim 7 , wherein a global gain adjustment dynamically increases the gain if a control error exceeds a threshold to improve the accuracy and decreases the gain if a system vibration is detected to eliminate the system vibration.

13 . The control method of claim 5 , wherein the model-based predictive controller combines the pump and valve DAC outputs from both the system model and the 2DOF PID controller to achieve optimal performance, wherein the resulting combination can be implemented as addition or weighted addition.

14 . The control method of claim 5 , wherein an alternative pump and valve configuration can used, such as an orifice for cuff air release, a constant output pump combined with a 3-way valve, wherein the 2DOF PID controller can be reduced to a one-degree-of-freedom (1DOF) PID controller, wherein the cuff plant can be reduced to use the valve electromechanical properties only.

15 . An extraction method of measuring arterial pressures of a subject for a continuous blood pressure measurement device for measuring blood pressure, the method comprising:

providing a cuff that is configured to fit on a blood pressure measurement site to compress an artery of the measurement site;

increasing and decreasing a pressure inside the cuff using an inflation/deflation unit that consists of a piezoelectric pump and a valve;

detecting a cuff pressure using a pressure detection unit, which is the pressure inside the cuff;

generating photoplethysmogram using at least one light-emitting diode and at least one photodiode;

detecting an arterial volume signal indicating a volume of the artery per unit length using a volume detection unit;

setting the cuff pressure by controlling the inflation/deflation unit using a control unit, wherein a model-based predictive controller comprises a system model and a 2DOF PID controller, wherein the system model incorporates arterial mechanical properties and cuff plant electromechanical properties, wherein a global gain adjustment is used to prevent system vibration and improve performance;

and measuring volume waveform and blood pressure waveform to detect systolic with systolic timing, diastolic with diastolic timing, and MAP of a subject using an extraction unit, wherein a bilinear transformation is used for error correction, wherein a volume setpoint corresponds to the cuff pressure below the mean arterial pressure to prevent skin discoloration, wherein the extraction unit is further configured to construct a true blood pressure waveform using a lower cuff pressure to improve subject comfort.

16 . The extraction method of claim 15 , wherein the bilinear transformation for error correction is configured for increasing accuracy of the blood pressure measured.

17 . The extraction method of claim 15 , wherein the arterial volume setpoint corresponds to a lower cuff counter pressure than a pressure corresponding to the mean arterial pressure (MAP), to improve patient comfort.

18 . The extraction method of claim 15 , wherein the arterial blood pressure reconstruction method uses the arterial volume signal and the cuff pressure to reconstruct an arterial blood pressure of the subject.