Ex vivo calibration of a photoplethysmographic device
A method for calibration of a photoplethysmographic device including the steps of providing a fluid circuit ( 305 ) for blood or other liquid, a pump mechanism ( 310 ) to generate pulsatile flow of blood through the fluid circuit, a sample of excised tissue ( 315 ) in the fluid circuit through which the blood flows, and a photoplethysmographic device including an emitter and a photodetector ( 330 ) positioned on the tissue ( 335, 340 ) so that a portion of the light output by the emitter passes through the tissue and is incident on the photodetector. The method further includes the steps of energizing the pump mechanism ( 420 ) to move the blood through the tissue, energizing the emitter ( 425 ) to output light, collecting paired data from the photodetector and from one or more reference measurements ( 430 ), and processing the paired data to calibrate the photoplethysmographic device ( 435 ).
1. A method for in vitro calibration of a photoplethysmographic device comprising the steps of:
a. providing a fluid circuit;
b. incorporating a pump mechanism in the fluid circuit;
c. providing an excised tissue that includes at least one artery and a venous return portion;
d. configuring the pump mechanism to generate pulsatile output fluid flow through the fluid circuit;
e. connecting the pulsatile output fluid flow to the at least one artery of the excised tissue to incorporate the excised tissue in the fluid circuit;
f. providing a photoplethysmographic device including an emitter and a photodetector;
g. positioning the emitter so that light output by the emitter is incident on the excised tissue;
h. positioning the photodetector so that a portion of the light output by the emitter passes through the excised tissue and is incident on the photodetector;
i. introducing blood into the fluid circuit to be input to the pump mechanism;
j. incorporating a sample access port in the fluid circuit for sampling the blood in the fluid circuit and for running the sampled blood through a reference instrument to obtain reference measurements;
k. energizing the pump mechanism to move the blood through the excised tissue;
l. energizing the emitter to output light;
m. pairing data from the photodetector and one or more reference measurements of the obtained reference measurements; and
n. processing the paired data to calibrate the photoplethysmographic device.
2. The method of claim 1 including the step of connecting the fluid circuit to the venous return portion of the excised tissue.
3. The method of claim 2 wherein the blood in the fluid circuit is enclosed to prevent exposure of the blood to ambient air.
4. The method of claim 1 including the step of incorporating a tonometer into the fluid circuit to set a partial pressure of one or more gases in the blood in the fluid circuit.
5. The method of claim 1 wherein the one or more reference measurements comprises reference measurements of blood analytes.
6. The method of claim 1 wherein the one or more reference measurements comprises reference measurements of hemodynamic parameters including at least one of heart rate, respiratory rate, circulating blood volume, perfusion index, and blood pressure.