Combined floormat and body-worn physiological sensors
The invention provides systems for measuring blood pressure and stroke volume values from a patient. Both systems feature a floormat system and a body-worn sensor working in concert. In aspects, the floormat generates calibrations for both blood pressure and stroke volume measurements. It features a base having a bottom surface configured to rest on or near a substantially horizontal surface, and a top surface configured to receive at least one of the patient's feet. Within the floormat are weight and blood pressure-measuring systems that determine, respectively, the calibrations for stroke volume and blood pressure. Its transmits these parameters to the body-worn sensor, which further processes them, along with other signals, to determine real-time values of blood pressure and stroke volume.
1. A system for measuring a stroke volume value from a patient, comprising:
a floormat system for measuring a stroke volume calibration, comprising:
a weight-measuring system comprising at least one strain gauge;
a processing system configured to receive a signal that comprises at least one of an output of the strain gauge and derived from the output of the strain gauge, and then process this to determine a stroke volume calibration; and
a first wireless system configured to wirelessly transmit information representing the stroke volume calibration; and
a body-worn sensor comprising:
an electrical impedance system comprising at least four electrodes, at least one of which is configured to inject an electrical current into the patient's body, and at least one of which is configured to measure a signal induced by the electrical current and representative of an impedance plethysmogram;
a second wireless system configured to receive information representing the stroke volume calibration; and
a processing system in electrical contact with the electrical impedance system and the second wireless system, and configured to receive signals from the electrical impedance system and convert them into a set of impedance values, the processing system further configured to analyze the set of impedance values and the stroke volume calibration to determine the stroke volume value.
2. The system of claim 1 , wherein the stroke volume calibration comprises a value representing the patient's weight.
3. The system of claim 2 , wherein the processing system comprises computer code configured to analyze the set of impedance values and the stroke volume calibration to determine the stroke volume value.
4. The system of claim 3 , wherein the computer code is configured to calculate a derivative of the set of impedance values to determine a dΔZ(t)/dt waveform.
5. The system of claim 4 , wherein the computer code is configured to determine a maximum value of the dΔZ(t)/dt waveform.
6. The system of claim 5 , wherein the computer code is configured to determine an area of a pulse in the dΔZ(t)/dt waveform.
7. The system of claim 4 , wherein the computer code is configured to estimate an ejection time from the dΔZ(t)/dt waveform.
8. The system of claim 4 , wherein the computer code is configured to estimate a baseline impedance (Z 0 ) from the set of impedance values.
9. The system of claim 8 , wherein the computer code is configured to determine: i) a maximum value of the dΔZ(t)/dt waveform ((dΔZ(t)/dt) max ); and ii) a left ventricular ejection time (LVET) from the dΔZ(t)/dt waveform.
10. The system of claim 9 , wherein the computer code is configured to determine stroke volume (SV) from the equation:
SV
~
(
d
ΔZ
(
t
)
/
dt
)
max
Z
o
×
LVET
.
11. The system of claim 9 , wherein the computer code is configured to determine stroke volume (SV) from the equation:
SV
~
(
d
ΔZ
(
t
)
/
dt
)
max
Z
o
×
LVET
.
12. The system of claim 4 , wherein the computer code is configured to determine stroke volume (SV) from the equation:
SV
=
V
c
×
(
d
ΔZ
(
t
)
/
dt
)
max
Z
o
×
LVET
where V c is a volume conductor calculated from the value of the patient's weight.
13. The system of claim 4 , wherein the computer code is configured to determine stroke volume (SV) from the equation:
SV
=
V
c
×
(
d
ΔZ
(
t
)
/
dt
)
max
Z
o
×
LVET
where V c is a volume conductor calculated from the value of the patient's weight.
14. The system of claim 1 , wherein the stroke volume calibration comprises a value representing the patient's body composition.
15. The system of claim 1 , wherein the first wireless system comprises a transmitter based on Bluetooth® or 802.11.
16. The system of claim 1 , wherein the second wireless system comprises a transmitter based on Bluetooth® or 802.11.
17. The system of claim 1 , wherein the electrical impedance system comprises an electrical system that injects a current modulated at a frequency between 25-125 kHz.
18. The system of claim 1 , wherein the electrical impedance system comprises an electrical system that comprises two electrodes that inject the electrical current into the patient.
19. The system of claim 18 , wherein the electrical impedance system comprises an electrical system that comprises two electrodes, each configured to measure a signal induced by the electrical current.