Medical fluid delivery devices and methods
A method including coupling a disposable device to a reusable device, wherein the disposable device includes: a heating segment including a fluid conduit including an inlet and an outlet, a first dielectric window at an upstream location, and a second dielectric window at a downstream location, wherein the reusable device includes: a receptacle configured to receive the disposable device, a first electrode positioned to be aligned with the first dielectric window, and a second electrode positioned to be aligned with the second dielectric window; supplying blood to the inlet to pass the blood through the fluid conduit; and activating the reusable device to cause the reusable device to apply an RF current between the first electrode and second electrodes, whereby the RF current is conducted into the fluid conduit through the first and second dielectric windows, thereby being conducted through the blood in the fluid conduit to heat the blood.
1 . A method, comprising:
coupling a disposable device to a reusable device,
wherein the disposable device comprises:
a heating segment, wherein the heating segment comprises:
a fluid conduit comprising an inlet and an outlet,
a first dielectric window into the fluid conduit at an upstream location that is proximate to the inlet, and
a second dielectric window into the fluid conduit at a downstream location that is proximate to the outlet,
wherein the reusable device comprises:
a receptacle configured to receive the disposable device,
a first electrode positioned within the receptacle, and
a second electrode positioned within the receptacle,
wherein the first electrode and the second electrode are spaced apart from one another to align the first electrode with the first dielectric window and to align the second electrode with the second dielectric window when the disposable device is received within the receptacle;
supplying blood to the inlet of the fluid conduit to result in the blood passing through the fluid conduit; and
activating the reusable device,
wherein the activating causes the reusable device to apply an RF current between the first electrode and the second electrode, and
wherein the RF current between the first electrode and the second electrode is conducted into the fluid conduit through the first dielectric window and the second dielectric window, thereby being conducted through the blood in the fluid conduit to result in heating of the blood in the fluid conduit.
2 . The method of claim 1 , wherein the first electrode and the second electrode are positioned within the receptacle so as to be on a same side of the fluid conduit when the receptacle receives the disposable device.
3 . The method of claim 1 , wherein during the method the reusable device and the disposable device are maintained at an orientation such that the outlet of the fluid conduit is positioned above the inlet of the fluid conduit.
4 . The method of claim 1 , wherein the blood in the fluid conduit is heated to a normothermic human body temperature.
5 . The method of claim 4 , wherein the blood in the fluid conduit is heated to the normothermic human body temperature with sufficient uniformity such that none of the blood is heated to a temperature above 42 degrees Celsius.
6 . The method of claim 1 , wherein the heating of the blood in the fluid conduit produces heated blood, and wherein the method further comprises supplying the heated blood to a patient.
7 . The method of claim 1 , wherein the first dielectric window and the second dielectric window comprise a dielectric material positioned to separate the blood in the fluid conduit from respective ones of the first and second electrodes.
8 . The method of claim 7 , wherein the dielectric material comprises a dielectric polymer having a relative permittivity that is in a range of between 2 and 12.
9 . The method of claim 8 , wherein the dielectric polymer comprises a fluorinated ethylene propylene film.
10 . The method of claim 1 , wherein each of the first electrode and the second electrode comprises a conductive material coated by an insulative coating.
11 . The method of claim 1 , wherein the RF current is impedance matched to an impedance of the blood.
12 . The method of claim 11 , wherein the RF current is impedance matched to the impedance of the blood by a process comprising:
performing an iterative process to initialize a heating system, wherein the iterative process comprises:
applying an RF current burst at a burst RF impedance between the first electrode and the second electrode,
measuring an initialization process reflected power between the first electrode and the second electrode resulting from the RF current burst;
if the initialization process reflected power is less than a predetermined threshold reflected power, concluding the iterative process and using the burst RF impedance as a heating RF impedance of the RF current; and
if the initialization process reflected power is greater than the predetermined threshold reflective power, reducing adjusting the burst RF impedance and repeating the iterative process.
13 . The method of claim 12 ,
wherein the blood is heated by a steady state heating process, wherein the steady state heating process comprises:
applying the RF current between the first electrode and the second electrode at the heating RF impedance and at a constant RF power for a duty cycle duration for each aliquot of blood;
wherein the RF current between the first electrode and the second electrode is conducted into the fluid conduit through the first dielectric window and the second dielectric window, thereby being conducted through the blood in the fluid conduit to result in heating of the blood in the fluid conduit, and wherein the duty cycle duration is controlled based on an inlet temperature, a target temperature, the heating RF impedance, the constant RF power, a volumetric heat capacity of the blood, and a volume of the aliquot to thereby cause the blood to be at the target temperature when the blood passes through the outlet of the fluid conduit;
measuring a steady state reflected power during heating of each aliquot of blood;
if the steady state reflected power is less than the predetermined threshold reflected power, continuing the steady state heating process; and
if the steady state reflected power is greater than the predetermined threshold reflected power, repeating the iterative process.
14 . The method of claim 12 , wherein an RF burst inductance is varied to thereby vary the RF burst impedance.
15 . The method of claim 14 , wherein the RF burst inductance is varied by varying an inductance of at least one variable inductor.