Body-worn system for continuous, noninvasive measurement of cardiac output, stroke volume, cardiac power, and blood pressure
The invention provides a system for measuring stroke volume (SV), cardiac output (CO), and cardiac power (CP) from a patient that features: 1) an impedance sensor connected to at least two body-worn electrodes and including an impedance circuit that processes analog signals from the electrodes to measure an impedance signal (e.g. a TBEV waveform); 2) an ECG sensor connected to at least two chest-worn electrodes and including an ECG circuit that processes analog signals from the electrodes to measure and ECG signal; 3) an optical sensor connected to a body-worn optical probe and including an optical circuit that processes signals from the probe to measure at least one optical signal (e.g. a PPG waveform) from the patient; 4) a processing system, typically worn on the patient's wrist and connected through a wired interface to the optical sensor, and through either a wired or wireless interface to the TBEV and ECG sensors. The processing system analyzes the ECG, TBEV and optical signals to determine SV, and further analyzes SV and HR determined from an ECG sensor to determine CO.
1. A method for measuring a time-dependent stroke volume (SV) value from a patient, comprising:
measuring a time-dependent impedance waveform from the patient using a transbrachial electro-velocimetry (TBEV) sensor worn on the patient's body;
measuring a time-dependent heart rate waveform from the patient using a heart rate sensor worn on the patient's body;
receiving the time-dependent impedance waveform and the time-dependent heart rate waveform at a processing component, wherein the processing component recursively determines time-dependent SV values by (i) processing the time-dependent impedance waveform to determine a value of Z 0 and a value of (dZ/dt) max , (ii) processing the time-dependent heart rate waveform to determine a value for systolic flow time (SFT); and (iii) collectively processing the value of Z 0 , the value of (dZ/dt) max and the value of SFT to determine a SV value; and
displaying the time-dependent SV value on a display operably connected to the processing component.
2. The method of claim 1 , wherein the heart rate sensor is an electrocardiogram (ECG) sensor, and the time-dependent heart rate waveform is an ECG waveform.
3. The method of claim 1 , wherein the heart rate sensor is a photoplethysmogram (PPG) sensor, and the time-dependent heart rate waveform is a PPG waveform.
4. The method of claim 1 , wherein the processing component further processes a heart rate value determined from the time-dependent heart rate waveform and the time-dependent SV value to determine a time-dependent cardiac output (CO) value, and wherein the time-dependent CO value is displayed on the display.
5. The method of claim 1 , wherein the processing component is worn on the patient's body.
6. The method of claim 5 , wherein the display is a part of the processing component.
7. The method of claim 1 , wherein the display is remote from the processing component.
8. The method of claim 1 , wherein both an ECG sensor and a PPG sensor are worn on the patient's body and are both operably connected to the processing component.
9. The method of claim 8 , wherein the processing component further processes a time-dependent PPG waveform from the PPG sensor to determine a time-dependent SpO 2 value, and wherein the time-dependent SpO 2 value is displayed on the display.
10. The method of claim 9 , wherein the processing component further collectively processes a time-dependent ECG waveform from the ECG sensor and the time-dependent PPG waveform to determine a time-dependent mean arterial blood pressure (MAP) value, wherein the time-dependent MAP value is displayed on the display.
11. The method of claim 1 , wherein the processing component further processes the time-dependent impedance waveform to determine a time-dependent left ventricular ejection time (LVET) value.