Determination of the patient's blood volume at the start of dialysis treatment

Abstract

Embodiments of the present disclosure provide a method for determining a patient's starting blood volume during dialysis (e.g., hemodialysis). Ultrafiltration rate is determined at different timestamps during dialysis by obtaining blood flow rate measurements and hematocrit measurements at an input port and an output port of a dialyzer connected to the patient. Flow rate and hematocrit measurements are used to determine the fluid removed from the patient during dialysis. Ultrafiltration rate and fluid removed from the patient are used to determine the patient's starting blood volume.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] Priority is claimed to U.S. Patent Application No. 16 / 207,980, filed on December 3, 2018, the entire disclosure of which is incorporated herein by reference. Background Art

[0003] Patients with renal failure or partial renal failure often receive hemodialysis treatment in hemodialysis treatment centers or clinics. When healthy, kidneys maintain the internal balance of water and minerals (such as sodium, potassium, chloride, calcium, phosphorus, magnesium and sulfate) of the body. The kidneys also serve as a part of the endocrine system to produce erythropoietin and other hormones. Hemodialysis is an imperfect treatment that replaces kidney function, in part because it cannot correct the endocrine function of the kidney. The conventional method of performing dialysis is to estimate the amount of fluid that can be removed from the patient's body according to the weight of the patient when he arrives at conventional treatment. A rough estimate of "target" weight is determined by an algorithm using factors such as height, weight and other physiological conditions before the doctor orders dialysis treatment.

[0004] In hemodialysis, blood is extracted from the patient through an extraction needle (or catheter) that extracts blood from an artery located at a specific acceptable access location (arm, thigh, subclavian, etc.). The extracted blood is pumped through an extracorporeal tubing via a peristaltic pump and then passes through a special filter called a "dialyser". The dialyzer is designed to remove unwanted toxins from the blood, such as urea, nitrogen, potassium, and excess water in the blood. When the blood passes through the dialyzer, the blood travels in straw-like tubes that act as semi-permeable membrane channels for unpurified blood. Fresh dialysis fluid, a solution of chemicals and water, flows through the dialyzer in the opposite direction of blood flow. When the dialysate flows through the dialyzer, it surrounds the straw-like membrane in the dialyzer. These membranes have small holes that are large enough to allow liquid and liquid-based impurities to pass through, but not large enough to pass red blood cells. Fresh dialysate collects excess impurities through the straw-shaped tube by diffusion, and collects excess water through the ultrafiltration process due to the pressure drop across the membrane. During this process, the red blood cell volume is retained in the straw-shaped tube and then circulated back into the body. The used dialysate discharges excess fluid and toxins from the dialyzer via the output tube, thereby purifying the blood and red blood cells flowing through the dialyzer. The dialyzed blood then flows out of the dialyzer via a tube and a needle (or catheter) and returns to the patient's body. Sometimes, heparin drips or pumps are provided along the extracorporeal blood flow loop to prevent red blood cells from clotting during the hemodialysis process. During a typical treatment period of several hours, several liters of excess fluid can be removed. In the United States, chronic patients usually receive hemodialysis treatment three times a week in a dialysis center, either on a Monday-Wednesday-Friday schedule or on a Tuesday-Thursday-Saturday schedule. These center treatments usually take 3 to 4 hours to complete, and the blood flow rate usually exceeds 300ml / min. In other countries, the flow rate and treatment time are lower and longer, respectively.

[0005] Hemodialysis has a severe impact on the body's fluid balance due in part to the rapid changes in circulating blood volume. When the dialysis fluid removal rate is faster than the plasma refill rate of the stored plasma maintained by the body's internal tissues, the intravascular blood volume decreases. The resulting imbalance is associated with complications such as hypotension, loss of consciousness, headache, vomiting, dizziness, and cramps that patients experience during and after dialysis treatment that are similar to conventional blood loss. Continuous quantitative measurement of parameters related to the handling (real time) of blood volume during hemodialysis can reduce the chance of dialysis-induced hypotension and optimize dialysis treatment regimens by controlling fluid balance and helping patients achieve target dry weight.

[0006] Although dialysis involves the removal of fluids from the patient's body, there is no convenient way to obtain the patient's initial blood volume before treatment. Patients may go to a hospital or inpatient facility to measure blood volume using a dilution indicator. For example, a chemical sample is injected into the patient's blood, and then a blood sample is extracted using special equipment to determine the concentration of the chemical sample in the blood. Since dialysis clinics generally do not have a device for using a dilution indicator, the blood volume obtained in this manner may not be helpful because blood volume is a moving target. That is, before going to the dialysis clinic, a patient who pre-measured his blood volume may have lost blood volume due to exercise, or may have gained blood volume due to eating lunch. Therefore, the blood volume measurement obtained before arriving at the dialysis clinic may be very different from the patient's actual blood volume at the beginning of dialysis. Summary of the invention

[0007] One embodiment of the present disclosure provides a system for determining the starting blood volume of a patient undergoing dialysis treatment. The system includes: a first portion of a tube configured to connect the patient to an input of a dialyzer; a second portion of a tube configured to connect the patient to an output of the dialyzer; a pump configured to pump blood from the patient through the first portion of the tube into the dialyzer and out of the dialyzer into the second portion of the tube; a first blood chamber disposed along the first portion of the tube and a second blood chamber disposed along the second portion of the tube, wherein the first blood chamber and the second blood chamber are configured to facilitate hematocrit measurement; a controller configured to determine the starting blood volume using a hematocrit value associated with the input of the dialyzer, a hematocrit value associated with the output of the dialyzer, and a flow rate of blood through the first portion of the tube.

[0008] One embodiment of the present disclosure provides a method for determining a starting blood volume of a patient connected to a dialysis system. The method includes: using a pump of the dialysis system to circulate blood from the patient through a dialyzer; and using the dialysis system to determine the starting blood volume of the patient. Determining the starting blood volume includes: (a) determining a blood flow rate corresponding to an input side of the dialyzer; (b) determining a fluid removal rate at an initial time via the blood flow rate, the hematocrit corresponding to the input side of the dialyzer at an initial time, and the hematocrit corresponding to the output side of the dialyzer at an initial time; (c) determining a fluid removal rate after a first measurement period via the blood flow rate, the hematocrit corresponding to the input side of the dialyzer after a first measurement period, and the hematocrit corresponding to the output side of the dialyzer after the first measurement period; (d) determining a volume of fluid removed in the first measurement period via the fluid removal rate at the initial time and the fluid removal rate after the first measurement period; (e) determining a fractional blood volume change via the hematocrit corresponding to the input side of the dialyzer at an initial time and the hematocrit corresponding to the input side of the dialyzer after the first measurement period; and (f) determining the starting blood volume via the fractional blood volume change and the volume of fluid removed in the first measurement period.

[0009] One embodiment of the present disclosure provides a non-transitory computer-readable medium for determining a starting blood volume of a patient connected to a dialysis system. The non-transitory computer-readable medium includes instructions for causing a processor of the dialysis system to facilitate the following operations: using a pump of the dialysis system to circulate blood so that blood from the patient passes through a dialyzer; and using the dialysis system to determine the starting blood volume of the patient. Determining the starting blood volume includes: (a) determining a blood flow rate corresponding to an input side of the dialyzer; (b) determining a fluid removal rate at an initial time via the blood flow rate, the hematocrit corresponding to the input side of the dialyzer at an initial time, and the hematocrit corresponding to the output side of the dialyzer at an initial time; (c) determining a fluid removal rate after a first measurement period via the blood flow rate, the hematocrit corresponding to the input side of the dialyzer after a first measurement period, and the hematocrit corresponding to the output side of the dialyzer after the first measurement period; (d) determining a volume of fluid removed in the first measurement period via the fluid removal rate at the initial time and the fluid removal rate after the first measurement period; (e) determining a fractional blood volume change via the hematocrit corresponding to the input side of the dialyzer at an initial time and the hematocrit corresponding to the input side of the dialyzer after the first measurement period; and (f) determining the starting blood volume via the fractional blood volume change and the volume of fluid removed in the first measurement period. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a perspective view of a typical situation of a patient undergoing hemodialysis treatment using a non-invasive optical blood monitor that monitors the patient's blood in real time as the patient's blood passes through an extracorporeal circuit in a hemodialysis system;

[0011] Figure 2 An exemplary system for determining a patient's blood volume according to some embodiments of the present disclosure is shown;

[0012] Figure 3 A diagram showing a patient receiving hemodialysis treatment using a system configuration that can be used to determine a patient's blood volume according to some embodiments of the present disclosure; and

[0013] Figure 4 A process for determining a patient's blood volume according to some embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0014] Embodiments of the present disclosure provide a non-invasive method for determining a patient's blood volume during dialysis. Knowing a patient's blood volume at the start of dialysis can allow for better and more effective treatment of the patient than using an estimated baseline based on the patient's weight and height. A patient's blood volume at the start of dialysis can be tracked through various treatments to determine how the blood volume fluctuates over time. The blood volume at the start of dialysis can also inform how long the dialysis treatment should last.

[0015] Blood volume at the start of a dialysis treatment is a parameter that is not currently available to physicians in dialysis clinics. Therefore, embodiments of the present disclosure provide a method for benchmarking the condition of dialysis patients at the beginning of their dialysis session without invasive dye and / or isotope methods. Dyes and isotopes are not practical in dialysis clinics. These systems are not readily available in clinics, and based on the time required for dialysis, patients do not stay in the clinic long enough to perform these measurements. In addition, the cost of this type of measurement can be prohibitive and may not be available for every treatment. However, due to the success of a dialysis treatment, a patient may feel well after a dialysis treatment and not eat or drink appropriately before the next treatment session. Therefore, clinicians and physicians do not have an easily available baseline of a patient's fluid condition at the beginning of treatment to assess what adjustments may need to be made in the next session to achieve optimal fluid management. The embodiments disclosed herein provide an important benchmark of a patient's starting fluid volume. Before describing embodiments of the present disclosure, Figure 1 An example setup for a hemodialysis treatment is shown.

[0016] Figure 1is a perspective view of an exemplary patient undergoing hemodialysis treatment using a non-invasive optical blood monitor that monitors the patient's blood in real time as it passes through an extracorporeal circuit in a hemodialysis system. Figure 1 The environment shown in may be applicable to various exemplary embodiments of the present disclosure. In addition, it will be understood that Figure 1 The environment shown in is merely exemplary, and the principles discussed herein for exemplary embodiments of the present disclosure may also be implemented in other environments.

[0017] Figure 1 Patient 10 is shown receiving hemodialysis treatment using a hemodialysis system 12 and a non-invasive optical blood monitor 14. A typical hemodialysis clinic would have multiple hemodialysis systems 12 for treating patients on a Monday-Wednesday-Friday schedule or a Tuesday-Thursday-Saturday schedule. Although the present invention is not limited to the number of hemodialysis systems or specific types of hemodialysis systems located in a clinic, the general operation of the hemodialysis system 12 will aid in understanding the environment in which the present invention is intended to operate.

[0018] An input needle or catheter 16 is inserted into an access site of the patient 10, such as in an arm, and is connected to an extracorporeal line 18 leading to a peristaltic pump 20 and then to a dialyzer or blood filter 22. The dialyzer 22 removes toxins and excess fluid from the patient's blood. The post-dialysis volume of red blood cell blood is returned from the dialyzer 22 via an extracorporeal line 24 and a return needle or catheter 26. In some parts of the world (primarily the United States), the extracorporeal blood flow may additionally receive a heparin drip to prevent coagulation. Excess fluid and toxins are removed by a clean dialysis fluid, which is supplied to the dialyzer 22 via a tube 28 and removed via a tube 30 for disposal. In the United States, a typical hemodialysis treatment session takes approximately 3 to 5 hours.

[0019] exist Figure 1 In the exemplary environment shown, the optical blood monitor 14 includes a blood chamber 32, an optical blood sensor assembly 34, and a controller 35. The blood chamber 32 is preferably located upstream of the dialyzer 22 and in series with the extracorporeal tubing 18. Blood from the peristaltic pump 20 flows into the blood chamber 32 through the tubing 18. The preferred sensor assembly 34 includes an LED light emitter that emits luminescent light wavelengths to measure oxygenated hemoglobin (HbO2), hemoglobin (Hb), and H2O. For example, an LED of substantially 810 nm is isosbestic for red blood cell hemoglobin. The blood chamber 32 includes a lens so that the emitter and detector of the sensor assembly 34 can observe the blood flowing through the blood chamber 32 and determine the patient's real-time hematocrit value using ratiometric measurement techniques generally known in the art.

[0020] Figure 2An exemplary system 200 for determining a patient's starting blood volume for the start of dialysis treatment is shown in accordance with some embodiments of the present disclosure. The system 200 includes a hematocrit measurement engine 212, a flow rate measurement engine 214, and a blood volume engine 216.

[0021] Exemplary system 200 illustrates an example system that may incorporate Figure 1 and 3 . The hematocrit measurement engine 212, the flow rate measurement engine 214, and the blood volume engine 216 may be implemented in the hemodialysis system 12 and the non-invasive optical blood monitor 14. In this example configuration, the flow rate measurement engine 214 may be included in the hemodialysis system 12, the hematocrit measurement engine 212 is included in the optical blood monitor 14, and the blood volume engine 216 is included in the optical blood monitor 14 and / or the hemodialysis system 12. The hemodialysis system 12 and the optical blood monitor 14 may be communicatively coupled to each other to implement Figure 2 The relationships provided for system 200 may be used, or the desired parameters may be independently measured through discrete calculations.

[0022] For an integrated embodiment, the hematocrit measurement engine 212, the flow rate measurement engine 214, and the blood volume engine 216 correspond to hardware including one or more processors, such as a microprocessor or microcontroller. The hardware may also include non-transitory computer-readable media for temporary and / or permanent storage, such as read-only memory (ROM), random access memory (RAM), flash memory, and other computer memory and storage devices. In addition, the hematocrit measurement engine 212 can utilize one or more optical blood sensor assemblies, such as the optical blood sensor assembly 34, to measure the hematocrit value at the two main blood flow ports of the dialyzer 204. The blood volume engine 216 can be a computing device, such as the controller 35, which utilizes a processor and a storage device to determine the hematocrit value of the dialyzer 204, read the blood flow rate entering the dialyzer 204 from the processor in the dialysis machine 12, read the ultrafiltration pump rate of the dialysis machine 12, and then calculate the patient's starting blood volume at the beginning of dialysis.

[0023] exist Figure 2 In the system 200, as applied to Figure 3 , blood flows at a blood flow rate Q b The blood flows into the input port of the dialyzer 204. The blood flow rate is determined by the pump 202, which can be a peristaltic pump 20. Figure 3 Part of the dialysis machine 12. Figure 3 In the treatment setting, blood enters the dialyzer 204, undergoes a filtration process, and the filtered blood is filtered at a blood flow rate Q outThe difference between the blood flow rate at the input port of the dialyzer 204 and the blood flow rate at the output port of the dialyzer 204 is Figure 2 Indicated as Q UFR .exist Figure 3 In the treatment setting, Q out The flow rate is given by Q b Flow rate minus Q UFR The pumps on the dialysis machine 12 are calibrated and these calibration values ​​are readily available during the measurement. These flow rates can be arbitrary but should remain constant throughout the measurement.

[0024] There are several ways to determine the flow rate Q b .like Figure 2 As shown, in one embodiment, a flow meter 210 is provided in the extracorporeal circuit to measure Q b The measurements from the flow meter 210 may be provided to a flow rate engine 214 .

[0025] In another exemplary embodiment, flow meter 210 may or may not be provided, and Q b is determined by the calibrated pumping rate of the pump 202. The pump 202 may be operated at a specific number of rotations per minute that may match the commanded flow rate of blood entering the dialyzer 204. The pump 202 may provide the number of rotations per minute to the flow rate engine 214, which may then determine Q based on the number of rotations per minute. b .

[0026] In addition to determining the flow rate, the system 200 also determines the input port (HCT 206 ) and the output port (HCT) of the dialyzer 204 208 ) at the hematocrit. In one embodiment, the ratiometric measurement technique disclosed in U.S. Pat. No. 5,372,136, entitled “System and Method for Non-Invasive Hematocrit Monitoring,” which is incorporated herein by reference in its entirety, can be used to determine Figure 2 If an optical blood sensor assembly 34 is used, the hematocrit values ​​at positions 206 and 208 of the dialyzer 204 are measured. 206 ) at the hematocrit, the optical blood assembly 34 is moved to measure the output port (HCT) of the dialyzer 204. 208 ) at the hematocrit. If two optical blood sensor assemblies are used, one can measure HCT 206 , while the other measures HCT 208In some embodiments, non-invasive (no sample withdrawal required) hematocrit measurement can be used, e.g., using The system performs the measurement to obtain the hematocrit value.

[0027] The blood volume engine 216 receives the hematocrit measurement from the hematocrit measurement engine 212 and the flow rate measurement from the flow rate engine 214. Using the hematocrit measurement and the flow rate measurement, the blood volume engine 216 determines the total blood volume of the patient at the start of the dialysis treatment. The total blood volume of the patient at the start of the dialysis treatment is determined by dividing the total blood volume of the patient removed during the treatment time by the fractional blood volume change during the same treatment time. Using the measured hematocrit value HCT 206 and HCT 208 and blood flow rate Q b To determine the total blood volume removed and the fractional blood volume change.

[0028] Determining the total blood volume of a patient at time zero (TBV0) at the start of a dialysis treatment involves two sets of measurements, since there are two unknowns, TBV0 and the instantaneous total blood volume TBV(T) at treatment time T. For these measurements, it is assumed that the dialysis access is viable and that there is no recirculation from the vein to the arterial needle due to stenosis in or after the access.

[0029] For the first set of measurements, or Clip-on monitor (CLiC TM ) must be based on a calibrated blood parameter. For example, the ΔBV must be based on a calibrated hematocrit value that is accurate or traceable to any standard calibrated measurement of the hematocrit blood parameter.

[0030] In one embodiment, CLiC may be used TM The device performs a ΔBV measurement at position 206. A blood chamber may be placed at position 206 to facilitate use of CLiC TM In the manufacture of CLiC TM Each device will be measured on a matching blood chamber at the time of device assembly to verify the accuracy of the device’s hematocrit measurements using human blood from the manufacturing facility’s blood laboratory. TM The device is used here as an example of a hematocrit measurement engine 212. Since the measured hematocrit value is comparable to the laboratory hematocrit accuracy, the calibration state of the device can be used to make feasible measurements of ΔBV at any time point during dialysis treatment. The hematocrit (HCT) can be defined as Equation 1.

[0031]

[0032] Where HCT is the hematocrit, RBV is the red blood cell volume, and TBV is the total blood volume. Based on the mass balance condition that no red blood cell volume is lost in the dialyzer (only fluid is removed from the blood), the HCT measured at position 206 can be 206 to perform the calculation.

[0033] Initial HCT 206 It can be measured at the beginning of treatment (at time T=0) before being affected by fluid removal. From here, the initial HCT 206 is called HCT0 to distinguish it from the subsequent HCT 206 The measurement results are distinguished. According to Equation 1, HCT0 can be written as Equation 2.

[0034]

[0035] Where HCT0 is the initial hematocrit HCT measured at the start of treatment 206 , RBV is the red blood cell volume, and TBV0 is the initial total blood volume at the start of treatment (at time T=0).

[0036] At the duration T, the subsequent hematocrit can be measured. The hematocrit HCT measured at the duration T can be 206 Defined as Equation 3.

[0037]

[0038] Where HCT(T) is the hematocrit (HCT) measured at time T of treatment entry. 206 , RBV is the red blood cell volume, and TBV(T) is the total blood volume at time T entering treatment.

[0039] Equation 2 and Equation 3 can be rearranged to produce Equation 4 and Equation 5, respectively.

[0040]

[0041]

[0042] Since RBV is constant, Equation 4 and Equation 5 can be combined to calculate the fractional change in blood volume ΔBV as shown in Equation 6.

[0043]

[0044] ΔBV is based on a calibrated hematocrit value and is bounded by the accuracy of the hematocrit measurement. Rearranging Equation 6 provides Equation 7.

[0045] ΔBV×TBV0=TBV(T)-TBV0

[0046] TBV(T) = TBV0 × (ΔBV + 1) Equation 7

[0047] Equation 7 provides a relationship for the first set of measurements and provides a first equation involving two unknowns, the original patient blood volume TBV0 at the start of treatment and the patient blood volume TBV(T) at some time T into treatment. Solving Equation 7 determines the second set of measurements.

[0048] The second relationship between TBV0 and TBV(T) involves the approximate integral of the amount of blood volume fluid removed from time zero (i.e., from time T=0). That is, the total blood removed by ultrafiltration from time zero (e.g., start of treatment) to time T can be written as Equation 8. Equation 8 shows the volume of fluid removed according to the sampling integration technique based on timed samples.

[0049]

[0050] In Equation 8, Q UFR is the actual fluid removal rate in the dialysis circuit based on the ultrafiltration mechanism. Q UFR It is not the ultrafiltration rate of the ultrafiltration pump. Δt is the historical curve Q along the TBV(T) UFR The smaller Δt becomes, the more data the blood volume engine 216 processes and the more accurate the integral estimate of Equation 8 becomes. Time T is the total time into treatment, where Q UFR In active state. In order to use Equation 8, the ultrafiltration pump rate and the blood pump rate should maintain a steady state from the initial time T=0 to time T. In order to improve readability, the initial time T=0 is referred to as the initial time t0. In one embodiment, the rounding down of T / Δt can be regarded as the number of measurement cycles starting from the initial time t0.

[0051] Q UFR Volume change is the rate at which fluid is removed from the blood (in the dialyzer 204) into the dialysate. This should not be confused with the pump ultrafiltration rate value set for the ultrafiltration pump used to circulate the dialysate through the dialyzer 204. Because fluid removal from the patient's blood is accomplished by osmosis of the dialysis fluid through the dialyzer 204 outside the dialyzer fibers, while blood flow is confined within the dialyzer fibers, the actual fluid volume transfer Q UFRis not equal to the flow rate of dialysate passing outside the dialyzer fibers (ultrafiltration pump rate). The volume of fluid transferred depends not only on the ultrafiltration pump rate, but also on factors such as the efficiency of the dialyzer construction, the chemical composition of the dialysate, etc. The volume flow rate of fluid removed from the blood, Q UFR It is the additional portion of the spent dialysate volume that is removed from the dialyzer.

[0052] Solving Equation 8 for TBV(T) provides Equation 9, and setting Equation 7 equal to Equation 9 provides Equation 10.

[0053]

[0054]

[0055] Therefore, in order to determine the exact TBV0 by solving Equation 10, the actual Q UFR .Q UFR It can be measured from the process outlined below:

[0056] The dialysis blood pump is calibrated and the settings for moving blood through the dialyzer blood circuit are accurate. That is, the pump 202 should provide a calibrated pump volume flow rate Q b Typically, pumps used for dialysis are calibrated at their factory.

[0057] During the measurement cycle, the pump volume flow Q b It should remain unchanged from time t0 to time T.

[0058] Calibrated hematocrit sensor, e.g. or CLiC TM Device for measuring HCT 206 and HCT 208 As discussed previously, for Figure 1 In the setup, a sensor can be used to measure HCT 206 , which is then used to measure HCT 208 , or for Figure 3 In the setup, two sensors can be used to measure HCT simultaneously 206 and HCT 208 Both. Δt can be used to determine whether one sensor or two sensors are sufficient. If Δt is fairly large, such as 1 sample per minute or longer, a single sensor can be used to measure the hematocrit at two points, since the dialysis parameters do not change very quickly.

[0059] At periodic time intervals Δt, the dialysis pump is set to a constant and known Q b When HCT is measured 206 and HCT 208(If the hematocrit value does not change rapidly, the measurements are taken almost simultaneously.) While the hematocrit measurement is being taken, use Equation 6 and HCT 206 The fractional change in blood volume, ΔBV, was calculated.

[0060] Using the mass balance of the red cell volume flowing through the dialyzer (assuming no loss of red cell volume during time T), the following relationship can be derived to solve for Q UFR . Starting from position 206:

[0061]

[0062] Among them, HCT 206 is the calibrated measured hematocrit at position 206, RBVR is the red blood cell volume flow rate through the dialyzer, and Q b is the blood flow rate prescribed by the calibrated blood pump. A similar relationship can be written at position 208:

[0063]

[0064] Among them, HCT 208 is the calibrated measured hematocrit at position 208, RBVR is the red blood cell volume flow rate through the dialyzer, Q b is the calibrated blood flow rate, and Q UFR is the actual fluid removal volume flow rate.

[0065] Embodiments of the present disclosure use a hematocrit monitoring engine 212 to measure the hematocrit of blood entering the dialyzer 204 and then measure the hematocrit of HCT blood leaving the dialyzer 204. Due to the nature of the dialyzer 204, no red blood cells are lost across the dialyzer membrane within the dialyzer 204 - only fluids, such as urea, pass through and enter the waste collection dialysate. Since red blood cells do not pass through the dialysis membrane into the waste, a mass balance analysis of red blood cell volume is applicable. Assuming that the red blood cell volume is constant (i.e., no red blood cell volume is lost during time T), equations 11 and 12 can be combined to provide equation 13:

[0066] HCT 206 ×Q b =HCT 208 ×(Q b -Q UFR ) Equation 13

[0067] Equation 13 can be rearranged into Equation 14.

[0068]

[0069] Due to HCT 208and HCT 206 is the calibrated hematocrit value, and Q b is the calibrated flow rate of the blood pump 202, so from HCT 208 , HCT 206 and Q b The calibration value of Q is derived UFR is also the calibrated value. Samples n = 0 to 1 at a sampling rate of Δt can be used in equation 10 Q obtained and used UFR The values ​​are calculated to calculate multiple solutions of TBV0. Successive values ​​of TBV0 calculated for each measurement time nΔt may be averaged to improve the accuracy of the obtained TBV0.

[0070] The blood volume engine 216 determines TBV0 based on information received from the hematocrit measurement engine 212 and the flow rate engine 214 using the relationship shown in Equation 10 and Equation 14. Figure 2 , the dashed lines represent potential alternative inputs for determining flow rate, some or all of which may be used in different exemplary embodiments. For example, the blood flow rate at the input of the dialyzer 204 is desired, but this flow rate may be determined from the calibration pump 202 or the flow meter 210, so one of these measurement paths may be active while the other is inactive.

[0071] Figure 4 A process 400 for determining a patient's blood volume according to some embodiments of the present disclosure is shown. In step 402, the system 200 uses Q b (calibrated blood flow rate) and the hematocrit measurement HCT at time t0 206 and HCT 208 To determine the Q at the initial time t0 UFR (Actual Fluid Removal Rate). The blood volume engine 216 uses the HCT at time t0 from the hematocrit measurement engine 212 according to Equation 14 206 and HCT 208 and Q from the flow rate engine 214 b Determine Q at time t0 UFR The measured Q UFR Associated with time t0, and using a temporary variable To keep track of the total number of measurement cycles, the current or most recent measurement cycle, or the total number of TBV0 measurements that have been made. Initially, at time T=0, i is 0, and only after a period of time Δt has passed does i become 1. That is, it becomes 1 once T reaches Δt.

[0072] At step 404, after time Δt has elapsed, the blood volume engine 216 automatically increments i based on the above mathematical relationship and determines Q in a similar manner as has been discussed with respect to step 402. UFR The Q determined in step 404 UFR is the Q of measurement period i UFR .

[0073] At step 406, the blood volume engine 216 determines the difference in total blood volume between time t0 (T=0) and the accumulated measurement cycles between time T. That is, the blood volume engine 216 determines the fluid removed during the total number of measurement cycles that have passed within time T. Referring to Equation 8, the volume removed during a single measurement cycle is related to the previous Q UFR and the current Q UFR Add them, divide the result by 2, and then multiply the result by Q UFR The duration Δt between measurements. That is, using Q for measurement period i-1 UFR , Q for measurement period i UFR and Q for periods i-1 and i UFR The volume removed in measurement cycle i is then added to the total volume removed from time t0 to measurement cycle i-1 to obtain the total blood volume removed in the cumulative measurement cycles between time t0 and T.

[0074] For purposes of illustration, an example is provided. At time t0, the total volume removed is 0. In measurement cycle 1, the volume removed is calculated as TBV(1Δt)-TBV0. This value TBV(1Δt)-TBV0 is added to the previously removed total volume 0 to obtain the current total volume removed TBV(1Δt)-TBV0. In measurement cycle 2, the calculated volume removed is TBV(2Δt)-TBV(1Δt). This value TBV(2Δt)-TBV(1Δt) is added to the previously removed total volume TBV(1Δt)-TBV0 to obtain the current total volume removed TBV(2Δt)-TBV0. In this manner, in each successive measurement cycle, the difference in volume removed in the most recent measurement cycle is continuously calculated and added to the running total blood volume removed. Therefore, in step 406, the blood volume engine 216 determines the fluid removed from the cumulative measurement cycle from the initial time t0 to the most recent time T.

[0075] At step 408, the blood volume engine 216 determines the cumulative measurement period blood volume percentage change or blood volume fraction change ΔBV. ΔBV is determined according to Equation 6, where, at the initial time t0, HCT0 is the HCT 206 , and for the most recent measurement period i, HCT(T) is HCT206 Since the measurements are made at sampling intervals Δt, note that HCT(T) of the most recent measurement cycle i corresponds to HCT(iΔt).

[0076] At step 410 , the blood volume engine 216 determines and stores the TBV0 solution for the current measurement cycle i. The blood volume engine 216 determines the patient's starting blood volume TBV0 as defined in Equation 10 using the difference between ΔBV from step 408 and the total blood volume from step 406 .

[0077] At step 412, the blood volume engine 216 displays the stored TBV0 for the measurement period i and the current time T and / or the time iΔt at which the measurement was made.

[0078] At step 414, the blood volume engine 216 determines whether there are more measurement cycles. If more measurements are to be taken, a new Q is taken at step 404. UFR Measure, and increment i, otherwise at step 416, the blood volume engine 216 determines the average of the stored TBV0 solutions for measurement cycle 1 through measurement cycle i.

[0079] At step 418 , the blood volume engine 216 displays a data summary of all measurements taken during process 400 .

[0080] The user can determine a treatment plan for the patient or know how aggressive the dialysis treatment should be based on the values ​​the user obtains from the output of the hemodialysis system 12. If the patient's starting blood volume is significantly different from previous visits, the user (physician) can further provide the patient with additional tips on managing the total blood volume.

[0081] In an exemplary embodiment, the present invention provides a system for determining a starting blood volume of a patient undergoing dialysis treatment, the system comprising: a first portion of tubing configured to connect the patient to an input of a dialyzer; a second portion of tubing configured to connect the patient to an output of the dialyzer; a pump configured to pump blood from the patient through the first portion of tubing into the dialyzer and out of the dialyzer into the second portion of tubing; a first blood chamber disposed along the first portion of tubing and a second blood chamber disposed along the second portion of tubing, wherein the first blood chamber and the second blood chamber are configured to facilitate hematocrit measurement; and a controller configured to determine the starting blood volume using a hematocrit value associated with the input of the dialyzer, a hematocrit value associated with the output of the dialyzer, and a flow rate of blood through the first portion of tubing.

[0082] In another exemplary embodiment, the controller determines the flow rate of blood through the first portion of the tube by a calibrated pumping rate of the pump.

[0083] In another exemplary embodiment, the system further includes at least one of: a flow meter coupled to the first portion of the tube, the flow meter configured to be able to determine a flow rate of blood through the first portion of the tube.

[0084] In another exemplary embodiment, the system further includes a first sensor assembly coupled to the first blood chamber, the first sensor assembly being configured to measure a hematocrit value associated with an input of the dialyzer, and a second sensor assembly coupled to the second blood chamber, the second sensor assembly being configured to measure a hematocrit value associated with an output of the dialyzer.

[0085] In another exemplary embodiment, the controller is further configured to: determine a fractional change in the patient's blood volume using a hematocrit value associated with the input of the dialyzer at the beginning of the dialysis treatment and a hematocrit value associated with the input of the dialyzer at the end of the measurement period; determine a plurality of fluid removal volumetric flow rates during the measurement period using the hematocrit value associated with the input of the dialyzer, the hematocrit value associated with the output of the dialyzer, and the flow rate of blood through the first portion of the tubing; and determine a starting blood volume based on the fractional change in the patient's blood volume and the plurality of fluid removal volumetric flow rates.

[0086] In another exemplary embodiment, the controller is further configured to: determine an initial fluid removal volumetric flow rate of the plurality of fluid removal volumetric flow rates; and determine each successive fluid removal volumetric flow rate of the plurality of fluid removal volumetric flow rates at a sampling interval.

[0087] In another exemplary embodiment, the sampling interval is 1 minute or longer.

[0088] In another exemplary embodiment, the controller is further configured to: determine that the starting blood volume is an average of multiple starting blood volumes corresponding to multiple fluid removal volume flow rates; wherein the number of the multiple starting blood volumes is at least 2, and the number of the multiple fluid removal volume flow rates is at least 3.

[0089] In an exemplary embodiment, the present invention provides a method for determining a starting blood volume of a patient connected to a dialysis system, the method comprising: circulating blood from the patient through a dialyzer using a pump of the dialysis system; determining the starting blood volume of the patient using the dialysis system, wherein determining the starting blood volume comprises: determining a blood flow rate corresponding to an input side of the dialyzer; determining a fluid removal rate at an initial time via the blood flow rate, a hematocrit corresponding to the input side of the dialyzer at an initial time, and a hematocrit corresponding to an output side of the dialyzer at an initial time; determining a fluid removal rate after a first measurement period via the blood flow rate, the hematocrit corresponding to the input side of the dialyzer after a first measurement period, and the hematocrit corresponding to the output side of the dialyzer after the first measurement period; determining a removed fluid volume for the first measurement period via the fluid removal rate at the initial time and the fluid removal rate after the first measurement period; determining a fractional blood volume change via the hematocrit corresponding to the input side of the dialyzer at the initial time and the hematocrit corresponding to the input side of the dialyzer after the first measurement period; and determining the starting blood volume via the fractional blood volume change and the removed fluid volume for the first measurement period.

[0090] In another exemplary embodiment, determining the starting blood volume further comprises: displaying the starting blood volume on a screen of the dialysis system.

[0091] In another exemplary embodiment, determining the starting blood volume also includes: determining whether there are more measurement cycles; and in response to determining that there are more measurement cycles, the dialysis system performs: determining a fluid removal rate for a next measurement cycle via the blood flow rate, the hematocrit corresponding to the input side of the dialyzer after the next measurement cycle, and the hematocrit corresponding to the output side of the dialyzer after the next measurement cycle; determining a cumulative volume of removed fluid via the two most recent determined fluid removal rates and the removed fluid volume of the previous measurement cycle; determining a fractional blood volume change via the hematocrit corresponding to the input side of the dialyzer at an initial time and the hematocrit corresponding to the input side of the dialyzer for the next measurement cycle; and determining the starting blood volume via the fractional blood volume change and the cumulative volume of removed fluid.

[0092] In another exemplary embodiment, in response to determining that there are more measurement cycles, the dialysis system further performs: determining an average starting blood volume for all measurement cycles; and displaying the average of the plurality of starting blood volumes on a screen of the dialysis system.

[0093] In another exemplary embodiment, the blood flow rate corresponding to the input side of the dialyzer is determined via a calibrated pumping rate of the pump or an input flow meter of the dialysis system.

[0094] In another exemplary embodiment, the hematocrit corresponding to the input side of the dialyzer and the hematocrit corresponding to the output side of the dialyzer are measured via a first sensor assembly of the dialysis system and a second sensor assembly of the dialysis system, respectively.

[0095] In another exemplary embodiment, the hematocrit corresponding to the input side of the dialyzer is measured via the sensor assembly of the dialysis system, and after a period of time, the hematocrit corresponding to the output side of the dialyzer is measured via the sensor assembly of the dialysis system.

[0096] In another exemplary embodiment, each measurement cycle has a duration of 1 minute.

[0097] In an exemplary embodiment, the present invention provides a non-transitory computer-readable medium for determining a starting blood volume of a patient connected to a dialysis system, the non-transitory computer-readable medium comprising instructions for causing a processor of the dialysis system to facilitate the following operations: circulating blood from the patient through a dialyzer using a pump of the dialysis system; and determining the starting blood volume of the patient using the dialysis system, wherein determining the starting blood volume comprises: determining a blood flow rate corresponding to an input side of the dialyzer; and determining the fluid volume at the initial time via the blood flow rate, the hematocrit corresponding to the input side of the dialyzer at an initial time, and the hematocrit corresponding to the output side of the dialyzer at an initial time. removal rate; determining the fluid removal rate after the first measurement period via the blood flow rate, the hematocrit corresponding to the input side of the dialyzer after the first measurement period, and the hematocrit corresponding to the output side of the dialyzer after the first measurement period; determining the volume of the removed fluid of the first measurement period via the fluid removal rate at the initial time and the fluid removal rate after the first measurement period; determining the fractional blood volume change via the hematocrit corresponding to the input side of the dialyzer at the initial time and the hematocrit corresponding to the input side of the dialyzer after the first measurement period; and determining the starting blood volume via the fractional blood volume change and the volume of the removed fluid of the first measurement period.

[0098] In another exemplary embodiment, determining the starting blood volume further comprises: displaying the starting blood volume on a screen of the dialysis system.

[0099] In another exemplary embodiment, determining the starting blood volume also includes: determining whether there are more measurement cycles; and in response to determining that there are more measurement cycles, the dialysis system performs: determining the fluid removal rate for the next measurement cycle via the blood flow rate, the hematocrit corresponding to the input side of the dialyzer after the next measurement cycle, and the hematocrit corresponding to the output side of the dialyzer after the next measurement cycle; determining the cumulative volume of the removed fluid via the two most recent determined fluid removal rates and the volume of the removed fluid in the previous measurement cycle; determining the fractional blood volume change via the hematocrit corresponding to the input side of the dialyzer at the initial time and the hematocrit corresponding to the input side of the dialyzer in the next measurement cycle; and determining the starting blood volume via the fractional blood volume change and the cumulative volume of the removed fluid.

[0100] In another exemplary embodiment, in response to determining that there are more measurement cycles, the dialysis system further performs: determining an average starting blood volume for all measurement cycles; and displaying the average of the plurality of starting blood volumes on a screen of the dialysis system.

[0101] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0102] The use of the terms "one" and "an" and "the" and "at least one" and similar indicators in the context of describing the present invention (particularly in the context of the appended claims) will be interpreted as covering singular and plural forms, unless otherwise specified herein or clearly contradicted by the context. The term "at least one" followed by a list of one or more items (e.g., "at least one of A and B") should be understood to represent an item (A or B) selected from the listed items or any combination of two or more of the listed items (A and B), unless otherwise specified herein or clearly contradicted by the context. Unless otherwise specified, the terms "comprising", "having", "including" and "containing" should be interpreted as open terms (i.e., meaning "including but not limited to"). Unless otherwise specified herein, the description of the numerical range herein is intended only to be used as a shorthand method for individually referring to each individual value falling within the range, and each individual value is incorporated into this specification as if it were recorded separately herein. Unless otherwise specified herein or clearly contradicted by the context, all methods described herein can be performed in any suitable order. Unless otherwise stated, the use of any and all examples or exemplary language (e.g., "such as") provided herein is intended only to better illustrate the present invention and is not intended to limit the scope of the present invention. No language in the specification should be construed as indicating that any unclaimed element is essential to the practice of the present invention.

[0103] Preferred embodiments of the present invention are described herein, including the best mode known to the inventor for implementing the present invention. Upon reading the foregoing description, variations of those preferred embodiments may become apparent to those of ordinary skill in the art. The inventor expects that skilled technicians will appropriately adopt these variations, and the inventor wishes that the present invention be implemented in a manner different from that specifically described herein. Therefore, the present invention includes all modifications and equivalents of the subject matter described in the appended claims as permitted by applicable law. In addition, unless otherwise specified herein or clearly contradictory to the context, the present invention encompasses any combination of the above-mentioned elements in all possible variations thereof.

Claims

1. A system for determining a starting blood volume of a patient undergoing dialysis treatment, the system comprising: a first portion of tubing configured to connect a patient to an input port of the dialyzer; a second portion of tubing configured to connect a patient to an output port of the dialyzer; a pump configured to pump blood from the patient through the first portion of tubing into the dialyzer and out of the dialyzer into the second portion of tubing; a first blood chamber disposed along a first portion of the tube, and a second blood chamber disposed along a second portion of the tube, wherein the first blood chamber and the second blood chamber are configured to facilitate hematocrit measurement; and A controller is configured to determine a starting blood volume using a measured hematocrit value associated with an input port of the dialyzer, a measured hematocrit value associated with an output port of the dialyzer, and a measured flow rate of blood through the first portion of the tubing, wherein the starting blood volume is the patient's blood volume at the start of a dialysis treatment.

2. The system according to claim 1, wherein: The controller determines the flow rate of blood through the first portion of the tube by a calibrated pumping rate of the pump.

3. The system according to claim 1, wherein: The system further comprises: A flow meter is coupled to the first portion of tubing, the flow meter being configured to measure a flow rate of blood through the first portion of tubing.

4. The system according to claim 1, wherein: The system further comprises: a first sensor assembly coupled to the first blood chamber, the first sensor assembly configured to measure a hematocrit value associated with an input port of the dialyzer; and A second sensor assembly is coupled to the second blood chamber, the second sensor assembly being configured to measure a hematocrit value associated with an output port of the dialyzer.

5. The system according to claim 1, wherein: The controller is also configured to: determining a fractional change in the patient's blood volume using a hematocrit value associated with an input port of the dialyzer at the beginning of the dialysis treatment and a hematocrit value associated with the input port of the dialyzer at the end of the measurement period; determining a plurality of fluid removal volumetric flow rates during the measurement period using a hematocrit value associated with an input port of the dialyzer, a hematocrit value associated with an output port of the dialyzer, and a blood flow rate through the first portion of the tubing; as well as A starting blood volume is determined based on the fractional change in the patient's blood volume and the plurality of fluid removal volumetric flow rates.

6. The system according to claim 5, wherein: The controller is also configured to: determining an initial fluid removal volumetric flow rate among the plurality of fluid removal volumetric flow rates; and Each successive fluid removal volumetric flow rate of the plurality of fluid removal volumetric flow rates is determined at a sampling interval.

7. The system according to claim 6, wherein: The sampling interval is 1 minute or longer.

8. The system according to claim 5, wherein: The controller is also configured to: determining the starting blood volume as an average of a plurality of starting blood volumes corresponding to the plurality of fluid removal volumetric flow rates; Wherein, the number of the multiple starting blood volumes is at least 2, and the number of the multiple fluid removal volume flow rates is at least 3.

9. A non-transitory computer readable medium for determining a starting blood volume of a patient connected to a dialysis system, the non-transitory computer readable medium comprising instructions for causing a processor of the dialysis system to: The dialysis system's pump is used to circulate blood from the patient through the dialyzer; and The patient's starting blood volume is determined using the dialysis system, where Determining the initial blood volume includes: measuring a blood flow rate corresponding to an input port side of the dialyzer; determining a fluid removal rate at an initial time via the blood flow rate, a measured hematocrit at an initial time corresponding to an input port side of the dialyzer, and a measured hematocrit at an initial time corresponding to an output port side of the dialyzer; determining a fluid removal rate after the first measurement period via the blood flow rate, a measured hematocrit corresponding to an input port side of the dialyzer after the first measurement period, and a measured hematocrit corresponding to an output port side of the dialyzer after the first measurement period; determining a volume of fluid removed during a first measurement period via a fluid removal rate at the initial time and a fluid removal rate after the first measurement period; determining a fractional blood volume change via a measured hematocrit corresponding to an input port side of the dialyzer at an initial time and a measured hematocrit corresponding to the input port side of the dialyzer after a first measurement cycle; and determining a starting blood volume via the fractional blood volume change and the volume of fluid removed of the first measurement cycle, The initial blood volume is the patient's blood volume at the beginning of dialysis treatment.

10. The non-transitory computer readable medium of claim 9, wherein: Determining the initial blood volume further comprises: The starting blood volume is displayed on the screen of the dialysis system.

11. The non-transitory computer readable medium of claim 9, wherein: Determining the initial blood volume further comprises: determining whether more measurement cycles exist; and In response to determining that more measurement cycles exist, executing, by the dialysis system: determining a fluid removal rate for a next measurement cycle via the blood flow rate, the hematocrit corresponding to the input port side of the dialyzer after the next measurement cycle, and the hematocrit corresponding to the output port side of the dialyzer after the next measurement cycle; determining a cumulative volume of fluid removed via the determined two most recent fluid removal rates and the volume of fluid removed for a previous measurement period; determining a fractional blood volume change via a hematocrit corresponding to an input port side of the dialyzer at an initial time and a hematocrit corresponding to an input port side of the dialyzer at a next measurement cycle; and The starting blood volume is determined via the fractional blood volume change and the cumulative volume of fluid removed.

12. The non-transitory computer readable medium of claim 11, wherein: In response to determining that there are more measurement cycles, the dialysis system further performs: determining the average starting blood volume for all measurement cycles; and The average of the multiple starting blood volumes is displayed on the screen of the dialysis system.

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