System and method for tracking fluid transit time in a conduit

Abstract

A method of tracking fluid in a conduit includes converting a volume of the conduit to an equivalent fluid particle count and discretizing a fluid flow in the conduit into discrete, quantifiable fluid particles based on a resolution of a sensor assembly connected to an exit of the conduit. The method includes recording entry timestamps for each of the fluid particles upon passing an entrance to the conduit. A real-time movement of each of the fluid particles between the entrance of the conduit and an exit of the conduit is determined, and an analyte measurement for each of the fluid particles is determined. A transit time for each of the fluid particles is determined and displayed along with the analyte measurement for each of the fluid particles.

Description

Atorney Docket No.: 105053-201SYSTEM AND METHOD FOR TRACKING FLUID TRANSIT TIME IN A CONDUITCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 693,747, filed September 12, 2024, and U.S. Provisional Patent Application No. 63 / 878,582, filed on September 9, 2025, which are incorporated by reference as if disclosed herein in their entireties.BACKGROUND

[0002] Acute Kidney Injury (AKI) is a common and yet severe complication of major surgery, such as cardiac surgery, with 40-50% of cardiac patients being affected. AKI not only increases patients’ morbidity and mortality but also prolongs hospital stays, leading to an overall increase in healthcare costs. Globally, over 13 million cases of AKI are seen every year, resulting in about 1.7 million deaths. In the U.S., AKI costs taxpayers an estimated $24 billion in additional healthcare expenses annually. In severe cases, AKI may require renal replacement therapy, such as dialysis. Diagnosing AKI is challenging because the established clinical markers of AKI, such as serum creatinine and urine output, often fail to provide a timely diagnosis and only provide an indication of kidney damage after a significant decline in kidney function has already occurred.

[0003] However, decreased renal oxygenation is a major contributor to AKI since the medulla of the kidney is highly susceptible to hypoxia, especially during reduced renal perfusion in trauma or cardiac surgery. Urinary oxygen partial pressure (PuCh) is an effective surrogate for assessing renal medullary oxygenation, and continuous, real-time monitoring of urinary PuCh may serve as an early indicator of renal hypoxia, enabling preventive interventions. Urinary PuCh is best measured in patients who have a urinary catheter placed. However, the current technology cannot account for the varying transit times of individual packets of urine. As the urine flows through the catheter, flow variability can lead to prolonged and varying urine packet transit times. When the flow rate suddenly increases, these older urine packets are flushed out quickly. Relying solely on the flow rate at the catheter's end can lead to incorrect assumptions about the age of the urine packets exiting the catheter. For example, a sudden high flow rate may suggest that the exiting urine is fresh when, in reality, it may be an older packet that has been stagnant in the catheter for a considerable time. Conversely, a low flow rate might imply the urine is old when it could be a fresh packet slowly passing through. Accordingly, the varying transit times of the urine packets may result in distorted PuCh measurements, thereby decreasing the reliability of the PuCh measurements for monitoring renal oxygenation.132320064.4Atorney Docket No.: 105053-201SUMMARY

[0004] Aspects of the present disclosure are directed to methods of real-time monitoring and tracking of urine packet transit time within urinary catheters. This technology is crucial for determining the validity of urine samples for clinical interventions, particularly in monitoring renal oxygen levels to predict acute kidney injury (AKI). The problem of urine age determination by introducing a system and method that accurately tracks the transit time of urine packets within catheter assemblies. Unlike methods that only measure flow rate, some embodiments of the system and method determine the transit time, ensuring that a patient monitor can reliably assess the appropriateness of using oxygen measurement to estimate bladder and / or renal tissue oxygen concentration. In addition, embodiments of the disclosure system and method may also provide clinicians with information on how old a particular urine sample is that they are drawing. This capability is important for making informed decisions about the validity of measurements from urine samples for clinical interventions, particularly in monitoring renal oxygen levels and predicting AKI. By providing real-time monitoring and validation, some embodiments of the disclosed system and method enhance the quality and reliability of clinical data, leading to better patient outcomes.

[0005] Aspects of the present disclosure are directed to embodiments of a method of tracking fluid in a conduit, channel, catheter, cannula, tube, or other similar structure configured to carry a fluid. In some embodiments, the method includes converting a volume of the conduit to an equivalent fluid particle count. In some embodiments, the method includes discretizing a fluid flow in the conduit into discrete, quantifiable fluid particles based on the resolution of a sensor assembly that is connected to an exit of the conduit. Some embodiments of the method include recording an entry timestamp for each of the fluid particles upon passing through the entrance of the conduit. In some embodiments, the method includes determining real-time movement of each of the fluid particles between the entrance of the conduit and an exit of the conduit. Some embodiments of the method include performing an analyte measurement for each of the fluid particles and determining a transit time for each of the fluid particles. Some of the embodiments of the method include displaying the analyte measurement and the transit time for each of the fluid particles.

[0006] In some embodiments of the method, the determining of the real-time movement of each fluid particle between the entrance of the conduit to the exit of the conduit further includes determining a real-time movement of each of the fluid particles from the entrance of the conduit to the exit during forward flow in the conduit and determining a real-time movement of each of the fluid particles back towards the entrance of the conduit during a reverse flow in the conduit.232320064.4Atorney Docket No.: 105053-201 In some embodiments, the method further includes reintegrating fluid particles reversed back through the entrance of the conduit during the reverse flow when said fluid particles reenter the conduit during a subsequent forward flow. In some embodiments of the method, determining the real-time movement of each of the fluid particles between the entrance of the conduit and the exit of the conduit includes tracking the movement of each of the fluid particles using a deque. In some embodiments, the method further includes structuring the sensor assembly to comprise a flow sensor. In some embodiments, the method further includes structuring the sensor assembly to comprise an oxygen sensor. In some embodiments of the method, the fluid comprises urine and the analyte measurement comprises urinary oxygen partial pressure.

[0007] Aspects of the disclosure are directed to embodiments of a system for tracking fluid in a conduit. In some embodiments, the system includes a conduit assembly including a conduit extending from a first end to a second end, where the first end is positioned in a fluid reservoir. In some embodiments of the system, the conduit assembly includes a sensor assembly fluidly connected to the second end of the conduit and a collector fluidly connected to the sensor assembly and structured to collect fluid passing through the sensor assembly. Some embodiments of the system include a controller configured to receive information from the sensor assembly and programmed to execute a series of instructions. In some embodiments of the system, the controller is programmed to convert a measured or sensed volume of the fluid to an equivalent fluid particle count and discretize a fluid flow in the conduit into discrete, quantifiable fluid particles based on a resolution of the sensor assembly. In some embodiments of the system, the controller is further programmed to record an entry timestamp for each of the fluid particles upon entering the conduit. In some embodiments of the system, the controller is programmed to determine a real-time movement of each of the fluid particles between the entrance of the conduit and the exit of the conduit. In some embodiments of the system, the controller is programmed to receive analyte measurements for each of the fluid particles from the sensor assembly, determine a transit time for each of the fluid particles, and display the analyte measurement and transit time for each of the fluid particles.

[0008] In some embodiments of the system, the sensor assembly includes a flow sensor structured to measure a flow of fluid particles at the second end of the conduit. In some embodiments of the system, the sensor assembly includes an oxygen sensor structured to measure an oxygen partial pressure for each of the fluid particles leaving the second end of the conduit. In some embodiments of the system, the real-time movement of each of the fluid particles between the entrance and the exit of the conduit further includes a movement of each of the fluid particles from the entrance to the exit of the conduit during forward flow in the conduit and a movement of each of the fluid 332320064.4Atorney Docket No.: 105053-201 particles back towards the entrance of the conduit during a reverse flow in the conduit. In some embodiments of the system, the controller is further programmed to reintegrate fluid particles reversed back through the entrance of the conduit during the reverse flow when said fluid particles reenter the conduit during a subsequent forward flow. In some embodiments of the system, the real-time movement of each of the fluid particles between the entrance of the conduit and an exit of the conduit is determined by tracking a movement of each of the fluid particles using a deque.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings show embodiments of the disclosed subject matter for the purpose of illustrating the invention. However, it should be understood that the present application is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:

[0010] FIG. 1 schematically illustrates an embodiment of a system for tracking fluid transit time in a conduit according to some embodiments of the present disclosure;

[0011] FIG. 2 illustrates an embodiment of fluid (urine) flow dynamics and fluctuations in a catheter placed in a cardiac patient during a cardiac surgery according to some embodiments of the present disclosure;

[0012] FIG. 3 schematically illustrates an embodiment of a method for tracking fluid transit time in a conduit according to some embodiments of the present disclosure;

[0013] FIG. 4 visually illustrates an embodiment of a particle-based algorithm for implementing embodiments of the system and method according to some embodiments of the present disclosure; and

[0014] FIG. 5 schematically illustrates an embodiment of a laboratory set-up used to assess a performance of the system and method according to some embodiments of the present disclosure.DETAILED DESCRIPTION

[0015] The following discussion relates to various embodiments of a system and method for tracking fluid transit time in a conduit. It will be understood that the herein described versions are examples that embody certain inventive concepts as detailed herein. To that end, other variations and modifications will be readily apparent to those of sufficient skill. The terms “about” or432320064.4Atorney Docket No.: 105053-201 “approximately” as may be used herein may refer to a range of 80%-125% of the claimed or disclosed value.

[0016] Accurate monitoring of urine oxygen concentration or urinary oxygen partial pressure (PuCh) and transit time through a urinary catheter is critical for assessing real-time renal oxygenation and identifying patients at risk for acute kidney injury (AKI). Monitoring urine oxygen concentration and transit time through the urinary catheter is a non-invasive way to determine renal stress during surgery and assist in early AKI risk detection.

[0017] While some of the embodiments described focus on tracking urine particles through a urinary catheter and measuring an analyte level, such as PuCh, of the urine, the systems and methods are not limited to such embodiments and may be used to track transit times of fluid particles through a tube, conduit, channel, or other such structure. In some embodiments, the fluid particles may be urine particles, however in some embodiments, the fluid particles may not be urine particles. Referring to FIG. 1, in some embodiments, a system 100 is shown for real-time monitoring and tracking of fluid particle transit time within conduits, tubes, channels, catheters, cannulas or other similar structures. In some embodiments, the system 100 includes a conduit assembly 10 and a controller 110. In some embodiments, the conduit assembly 10 may be used with a patient who is undergoing a surgical procedure. In some embodiments, the conduit assembly 10 includes a conduit 20, catheter, cannula, tube, channel, or other structure configured to hold and direct a fluid between a first end or entrance 22 and a second end 24 or exit. In some embodiments, the first end 22 is placed in or proximate to a fluid reservoir 302, and the second end 24 may be fluidly connected to a collector 40, such as a fluid bag. In some embodiments, the fluid reservoir 302 comprises a urinary bladder and the fluid comprises urine. In some embodiments, the second end 24 is fluidly coupled to a sensor assembly 50. In some embodiments, the sensor assembly 50 is at least partially embedded in the conduit 20. In some embodiments, the sensor assembly 50 includes a plurality of sensors configured to measure different properties or conditions of the fluid. In some embodiments, the plurality of sensors includes, but is not limited to sensors configured to measure temperature, fluid flow, and an analyte, such as oxygen. In some embodiments, the sensor assembly 50 comprises a flow sensor 52 that is configured to measure a flow of fluid exiting the conduit 20. In some embodiments, a drainage hose or drain 30 extends from a first end 32 that is fluidly coupled to the sensor assembly 50, including the flow sensor 52, and a second end 34 that is fluidly coupled to the collector 40. In some embodiments, the sensor assembly 50 may further include one or more analyte sensor 54 configured to measure an analyte in the fluid exiting the conduit 20. In some embodiments the analyte measurement pertains to a concentration, level, partial pressure, or other characteristic of the analyte. In some embodiments, 532320064.4Atorney Docket No.: 105053-201 the analyte sensor 54 comprises an oxygen sensor. In some embodiments, the oxygen sensor may comprise an optode-based oxygen sensor, which optically measures oxygen using any suitable optical measurement scheme, including luminescence.

[0018] In some embodiments, the controller 110 is in communication with the sensor assembly 50 connected to the conduit 20. In some embodiments, the controller 110 includes at least one central processing unit (CPU) 112 in communication with one or more memory units 114 configured to receive, analyze, and store information transmitted from the sensor assembly 50 pertaining to a flow of fluid in the conduit 20 and / or a distal analyte measurement. In some embodiments, the controller 110 is programmed to store and execute computer readable instructions via the CPU to receive, analyze, and transform information received from the sensor assembly 50. In some embodiments, the controller 110 is programmed to convert the volume of the conduit 20 to an equivalent fluid particle count. In some embodiments, the controller 110 is programmed to convert the volume of the conduit 20 to an equivalent urine particle count. In some embodiments, the conversion is done as shown in equation 1.Equation 1 : Cp= CmixkWhere:Cpis the conduit capacity of discrete fluid particles;Cmi is the volume of the conduit in milliliters; and k is a conversion factor.In some embodiments, the conversion factor k is determined according to equation 2.Equation 2: k = 10Nd(particles / mL), where Nd is the number of decimal places determined by the sensor’s resolution.

[0019] In some embodiments, the controller 110 is further programmed to discretize the fluid flow in the conduit 20 into discrete, quantifiable particles. In some embodiments, the discretizing of the fluid flow is based on the resolution of the sensor assembly 50. In some embodiments, the discretizing of the fluid flow is based on the resolution of the flow sensor 52. In some embodiments, the resolution of the sensor assembly 50 may depend on specifications of one or more of the sensors that comprise the sensor assembly 50. In some embodiments, the resolution of the sensor assembly 50 may depend on specifications of the flow sensor 52. In some embodiments, the resolution of the flow sensor depends on the intrinsic resolution and the bit-632320064.4Atorney Docket No.: 105053-201 length of the analog-to-digital (A / D) converter. In some embodiments, these specifications define the number of discrete subdivisions per milliliter. Accordingly, in some embodiments, a fluid packet or fluid particle is defined as one of these discrete subdivisions, where each fluid particle represents a fraction of the fluid volume.

[0020] In some embodiments, the conversion of the fluid flow rate data received by the sensor assembly 50 into a rate of fluid particles per second is done using equation 3. In some embodiments, the conversion of the fluid flow rate data received by the sensor assembly 50 into a rate of fluid particles per second enables the entry and exit of fluid particles to and from the conduit 20 to be tracked.Equation 3 : Np(i) = F (i) x kWhere:Npis the number of discrete particles entering the conduit per second at the ithtime step; andF (i) is the flow rate in milliliters per second at the ithtime step.

[0021] In some embodiments, the controller 110 is programmed to record a timestamp for each of the fluid particles corresponding to a respective time of entry into the conduit 20. In some embodiments, the controller 110 is programmed to track real-time movement of each of the fluid particles between the entrance 22 and exit 24 of the conduit 20 using measurements obtained from the sensor assembly 50 and an analysis using a double-ended queue (deque). A deque comprises a dynamic data structure, which allows for the insertion and deletion of elements, such as individual fluid particles, at both a front end and a rear end of the data structure. In some embodiments, the controller 110 is programmed to obtain and store information from the sensor assembly 50 pertaining to an analyte measurement in each of the fluid particles taken at the exit 24 (distal end) of the conduit 20 and to determine a corresponding transit time for each of the fluid particles. In some embodiments, the controller 110 is programmed to output or display the determined transit time along with the analyte concentration measured by the sensor assembly 50 for each of the fluid particles. For example, if the transit time of the fluid particle is 10 minutes and the analyte measurement is X, then the analyte measurement X may be displayed on a trendline at a time point of 10 minutes ago. In some embodiments, the display 116 is part of the controller 110. Determining the transit time enables the system 100 to account for transport delays through the conduit 20, which would result in distorted analyte measurements.732320064.4Atorney Docket No.: 105053-201

[0022] Referring to FIG. 2, an embodiment of fluid flow dynamics and fluctuations in a conduit 20 placed in a cardiac patient during a cardiac surgery is shown. In this embodiment, the fluid being measured is urine and the analyte measurement comprises urinary oxygen partial pressure (PuCh). As previously discussed, urine flow variability affects transit time of urine through the conduit 20, which in turn affects the reliability of PuCh measurements taken at the exit 24 of the conduit 20 for the purposes of monitoring renal oxygenation. The graph in FIG. 2 illustrates an example of the flow variability (measured in mL / hr) across each phase of the cardiac surgery. In some embodiments, such as shown in FIG. 2, the phases of cardiac surgery include a pre- cardiopulmonary bypass (Pre-CPB) phase, a cardiopulmonary bypass (CPB) phase, a post- cardiopulmonary bypass (Post-CPB) phase, and one or more a post-surgery phases. Still referring to FIG. 2, in some embodiments, a reverse urine flow is indicated with a negative flow rate and may result from patient movement. Accordingly, the varying urine flow rates may result in prolonged and varying transit times of urine through the conduit 20, which may distort PuCh measurements taken at the exit 22 of the conduit 20 using the sensor assembly 50. These distorted PuCh measurements may hinder an accurate determination of renal stress, which may reduce the ability to recognize the risk of AKI.

[0023] Since each urine particle experiences a range of flow rates during its transit time between the entrance 22 and the exit 24 of the conduit 20, a measurement of any single instantaneous flow rate, such as at a time point when the urine particle exits the conduit 20, is insufficient to characterize and consider transit time or transport delays. In order to determine an accurate indication of renal oxygenation, urine particles with shorter transit times are preferred as PuCh levels become less indicative of renal oxygenation as transit times through the conduit 20 increase. Accordingly, an advantage of some embodiments of the disclosed system and method is the ability to track individual fluid particles and determine the transit times for each of the individual fluid particles, which results in a more accurate determination of renal oxygenation.

[0024] Embodiments of a method 200 of real-time monitoring and tracking of fluid particle transit time within a conduit 20 will be discussed with reference to FIG. 3. In some embodiments, the volume of the conduit is determined. In some embodiments, the volume of the conduit 20 may be determined from manufacturer specifications. In some embodiments, the volume of the conduit 20 refers to the total volume of fluid that is held in the interior space or lumen of the conduit 20. In some embodiments, the volume of the conduit 20 is converted to an equivalent fluid particle count at step 202.832320064.4Atorney Docket No.: 105053-201

[0025] In some embodiments, fluid flow rates measured by the sensor assembly 50 are provided to the controller 110 (FIG. 1). In some embodiments, the fluid flow rate data obtained from the sensor assembly 50 is discretized or converted into a rate of fluid particles per second at step 204. In some embodiments, the conversion results in a number of discrete fluid particles entering the conduit 20 every second. In some embodiments, the fluid flow rate measurements from the flow sensor 52 are received and saved by the controller 110 until the number of fluid particles that have passed through the sensor assembly 50 is equal to or surpasses the volume of the conduit 20.

[0026] Referring to FIG. 4, an embodiment of the particle-based algorithm for tracking fluid transit time is shown schematically. As shown in this example, at time T=l, the conduit 20 is shown as having its total volume filled with fluid particles. In some embodiments, timestamps are recorded for each fluid particle as it enters the first end 22 of the conduit 20 at step 206 of FIG. 3. This is shown in the embodiment of FIG. 4 where tracking begins at T=2 with fluid particles A, B, and C entering the conduit 20 and each receiving a time stamp. In some embodiments, real-time movement of each fluid particle is tracked between the entrance 22 and the exit 24 of the conduit 20 at step 208 of FIG. 3 and as is further shown at times T=3-6 of FIG. 4. In some embodiments, tracking the movement of each fluid particle is done using a double-ended queue (deque), which is a dynamic data structure, which allows for the insertion and deletion of elements, such as individual urine particles, at both a front end and a rear end of the data structure.

[0027] Still referring to the embodiment of FIG. 4, at time T=3, the conduit 20 is filled with tracked fluid particles A-E. In an embodiment, at time T=4 of FIG. 4, particle A has been tracked to the conduit exit and to the flow sensor 52, which performs a flow measurement. Also, at time T=4, as shown in the embodiment of FIG. 4, particle F enters the conduit 20, and the remaining untracked particles UNK enter the drain 30. In some embodiments, at time T=5, particles G and H enter the conduit 20 and are given time stamps, particle A enters the drain 30, and particles B and C move through the flow sensor 52, where flow measurements are performed for each. In some embodiments, at time T=6, particles I-L enter the conduit 20 and are given time stamps, particles B and C enter the drain 30, and particles D-G move through the flow sensor 52, where flow measurements are performed for each. While the embodiment of FIG. 4 focuses on a flow of particles in a single direction, one can see how a flow of fluid in the opposite direction may be easily tracked. In some embodiments, tracking the flow of fluid in the opposite direction includes backing individual particles out of the conduit 20 and then reintegrating them when a forward flow begins again. Unlike currently used flow-based models, the disclosed systems and methods retain and utilize reintegrated particles if they hold clinical significance, rather than completely discarding data from negative or reverse flow as being invalid. In some embodiments, particle 932320064.4Atorney Docket No.: 105053-201 tracking proceeds until no longer needed, such as during the post-surgical phase indicated in FIG. 2.

[0028] Referring back to FIG. 3, in some embodiments, an analyte measurement for each fluid particle exiting the conduit 20 at step 210, and a corresponding transit time is determined for each fluid particle at step 212. In some embodiments, the transit time corresponds to the time it takes for a fluid particle to move from the entrance 22 to the exit 24 of the conduit 20. In some embodiments, the analyte measurement is obtained by an analyte sensor in the sensor assembly 50. In some embodiments, the transit time and analyte measurement for each fluid particle are displayed at step 214. In some embodiments, the transit times and analyte measurements for each of the fluid particles are displayed graphically.

[0029] The disclosed embodiments of the system and method are an improvement over the prior art by modeling the fluid flow as the movement of discrete particles and employing a deque structure for efficient and precise tracking of flow dynamics. In some embodiments, the disclosed systems and methods simplify the tracking of fluid volumes, such as urine, particularly when a volume entering the conduit 20 does not leave the conduit 20 in the same volume due to fluctuations in the following fluid flows. In some embodiments, a volume of fluid entering the conduit 20 may split into several smaller volumes as it exits the conduit 20 if subsequent fluid flow rates are lower. In some embodiments, several small volumes of fluid entering the conduit 20 sequentially may exit the conduit 20 as a larger volume if subsequent fluid flow rates increase. Accordingly, by modeling the fluid flow as the movement of discrete particles, discrepancies in analyte measurements at the exit 24 of the conduit 20 caused by transit delays through the conduit 20 are better aligned with analyte measurements at or near the fluid reservoir 302. When embodiments of the disclosed systems 100 and methods 200 are used to track urine transit time in a urinary catheter, discrepancies in PuCh measurements at the exit of the urinary catheter caused by transit delays through the urinary catheter are better aligned with the medullary oxygen levels.

[0030] Some embodiments of the method 200 were assessed using controlled laboratory setups. In some embodiments, the laboratory set up 300 is configured as shown in FIG. 5, and includes a reservoir 302, a first tube 320 representing the conduit 20 (FIGS. 1 and 4), and a second tube 330 emptying into a receptacle or collector 340. In some embodiments, the first tube 320 extends from a first end 322 that is fluidly coupled to the reservoir 302 to a distal end or second end 324 that is coupled to a flow sensor 306. In some embodiments, the second tube 330 extends from a first end 332 that is coupled to the flow sensor 352 to a second end 334 that empties in to the receptacle 340. In some embodiments, the first and second tubes 320, 330 comprise an inner diameter of1032320064.4Atorney Docket No.: 105053-201 about 4 mm. In some embodiments, the first tube 320 comprises a total length of 300 mm. In some embodiments, a plurality of oxygen sensors 354 are positioned to measure oxygen partial pressures at regular time intervals at various points along the setup 300. In some embodiments, an oxygen sensor 354 is positioned in the reservoir 302 and at the first and second ends 322, 324 of the first tube 320. In some embodiments, the reservoir 302 is at least partially filled with a fluid, such as water. In some embodiments, a mixture of oxygen and nitrogen gases are introduced into the fluid of the reservoir 302. In some embodiments, the fluid is treated to simulate urine with known and varying oxygen concentrations. In some embodiments, a valve 360 is positioned between the flow sensor 352 and the receptacle 340 and is configured to control a flow of fluid from the reservoir 302 through the first tube 320 at rates between 20 and 450 mL / h. In some embodiments, for each fluid flow rate, the oxygen concentration was initially set to a high value (100-120 mmHg), and the flow was started by opening the valve. In some embodiments, as the flow continued, the fluid's oxygen concentration was gradually decreased.

[0031] In some embodiments, the flow sensor 352 is in communication with a controller 110, such as a laptop computer, that is programmed to carry out embodiments of the method 200. In some embodiments, the plurality of oxygen sensors 354 are in communication with an oxygen monitor 370 and the controller 110. In some embodiments, the fluid flow rate was recorded every second. In some embodiments, after collecting data from the flow sensor 352 and oxygen sensors 354, an embodiment of the disclosed method 200 was carried out using the controller 110 to determine transit time for each fluid particle. In some embodiments, the transit time for each fluid particle was used to determine and apply a correction to the distal PuCE measurements for the delay introduced by fluid flow through the first tube 320. Some embodiments of the disclosed method 200 were carried out using the controller 110 to adjust each distal oxygen measurement by applying a time-shift corresponding to the computed transit time.

[0032] In some embodiments, the effectiveness of the transit time correction was evaluated by computing several quantitative error metrics between the corrected distal oxygen concentration and the actual proximal (entry) oxygen concentration as measured by the oxygen sensor 354 at Q shown in FIG. 5. In some embodiments, the root mean squared error (RMSE), the average error (bias), and the standard deviation (SD) of the error were computed. The variable transit time resulted in a substantial distortion in oxygen measurements (RMSE of 15.71 mmHg, SD of 12.72), a discrepancy comparable to the differences observed in PuCE between patients who later developed AKI and those who did not. In some embodiments, by modeling the variable transit time and applying the transit time correction, a marked improvement in measurement accuracy (RMSE reduced to 5.82 mmHg, SD of 5.55) was achieved, confirming that embodiments of the 1132320064.4Atorney Docket No.: 105053-201 system and method effectively compensate for such distortions. In some embodiments, a nearperfect Pearson correlation (r = 0.993) between the end oxygen measurements at W (FIG. 5) with the applied corrections and the start oxygen values at Q (FIG. 5), indicating that, independent of the flow rate, the correction reliably predicts the start oxygen concentration at Q (FIG. 5) from distal measurements at W (FIG. 5). Some embodiments of the system 100 and method 200 achieve this improvement by modeling the fluid flow as the movement of discrete particles and employing a deque structure for efficient and precise tracking of flow dynamics.

[0033] An advantage of such an approach is an overall simplification of tracking fluid volumes, particularly when a volume entering the conduit does not leave the same size due to fluctuations in the following fluid flows. Some embodiments of the systems 100 and methods 200 result in an improved alignment of analyte measurements at the conduit entrance and exit 22, 24 (FIG. 1), which reduces discrepancies caused by transit delays through the conduit 20 (FIG. 1). In some embodiments, the improved alignment is noticeable across a wide range of fluid flow rates, which highlights the robustness of embodiments of the disclosed system 100 and method 200 in the face of variable conditions. This robustness is of particular importance in real-world clinical scenarios, e.g., during cardiac surgery and trauma care, where flow rates vary significantly due to patientspecific factors such as physiological responses, procedural interventions, or patient movements. In some embodiments of the system 100 and method 200, small amounts of air entering the conduit 20 may be detected by the sensor assembly 50 (particularly the flow sensor). In some embodiments of the system 100 and method 200, such measurements associated with the small amounts of air are excluded, which further maintains reliability.

[0034] Current systems and methods used to measure renal oxygenation, such as continuous-flow systems and models, do not account for dynamic changes in flow rates (especially for low flow rates) and often discard data that could be useful, resulting in less reliable measurements. By employing embodiments of the disclosed systems 100 and methods 200 to discretize the urine flow into particles and dynamically adjusting for flow rate changes, the resulting oxygen concentration measurements accurately reflect the underlying physiological state. Moreover, some embodiments of the system 100 and method 200 provide the groundwork for broader applications in medical monitoring systems, including fluid dynamics and real-time physiological assessments. Moreover, some embodiments of the disclosed methodology may be adapted to monitor other fluid dynamics where accounting for widely fluctuating flow rates is important.

[0035] Although the invention has been described and illustrated with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and1232320064.4Atorney Docket No.: 105053-201 various other changes, omissions, and additions may be made therein and thereto, without parting from the spirit and scope of the present invention.1332320064.4

Claims

Atorney Docket No.: 105053-201CLAIMSWhat is claimed is:

1. A method of tracking a fluid in a conduit, comprising: converting a volume of the conduit to an equivalent fluid particle count; discretizing a fluid flow in the conduit into discrete, quantifiable fluid particles based on a resolution of a sensor assembly connected to an exit of the conduit; recording an entry timestamp for each of the fluid particles upon entering the conduit; determining real-time movement of each of the fluid particles between the entrance of the conduit and an exit of the conduit; performing an analyte measurement for each of the fluid particles at the exit of the conduit; determining a transit time for each of the fluid particles; and displaying the analyte measurement and corresponding transit time for each of the fluid particles.

2. The method of claim 1, wherein the determining of the real-time movement of each of the fluid particles between the entrance of the conduit to the exit of the conduit further comprises: determining real-time movement of each of the fluid particles from the entrance of the conduit to the exit of the conduit during a forward flow in the conduit; and determining a real-time movement of each of the fluid particles back towards the entrance of the conduit during a reverse flow in the conduit.

3. The method of claim 2, further comprising reintegrating fluid particles reversed back through the entrance of the conduit during the reverse flow when said fluid particles reenter the conduit during a subsequent forward flow.

4. The method of claim 1, wherein the determining the real-time movement of each of the fluid particles between the entrance of the conduit and an exit of the conduit comprises tracking a movement of each of the fluid particles using a deque.

5. The method of claim 1, further comprising structuring the sensor assembly to comprise a flow sensor.

6. The method of claim 1, further comprising structuring the sensor assembly to comprise an oxygen sensor.1432320064.4Atorney Docket No.: 105053-2017. The method of claim 1, wherein the fluid comprises urine and the analyte measurement comprises a urinary oxygen partial pressure.

8. A system for tracking a fluid in a conduit, comprising: a conduit assembly including, a conduit extending from a first end to a second end, wherein the first end is positioned in a fluid reservoir, a sensor assembly fluidly connected to the second end of the conduit, and a collector fluidly connected to the sensor assembly and configured to collect the fluid passing through the sensor assembly; and a controller configured to receive information from the sensor assembly and programmed to: convert a volume of the conduit to an equivalent fluid particle count; discretize a fluid flow in the conduit into discrete, quantifiable fluid particles based on a resolution of the sensor assembly; record an entry timestamp for each of the fluid particles upon entering the first end of the conduit; determine a real-time movement of each of the fluid particles between the first end of the conduit and the second end of the conduit; receive analyte measurements from the sensor assembly for each of the fluid particles leaving the second end of the conduit; determine a transit time for each of the fluid particles; and display the analyte measurement and the transit time for each fluid particle.

9. The system of claim 8, wherein the sensor assembly comprises a flow sensor configured to measure a flow of fluid particles at the second end of the conduit.

10. The system of claim 8, wherein the sensor assembly comprises an oxygen sensor configured to measure an oxygen partial pressure for each of the fluid particles leaving the second end of the conduit.

11. The system of claim 8, wherein the real-time movement of each fluid particle between the entrance of the conduit to the exit of the conduit further comprises: movement of each of the fluid particles from the entrance to the exit of the conduit during a forward flow in the conduit; and movement of each of the fluid particles back towards the entrance of the conduit during a reverse flow in the conduit.1532320064.4Attorney Docket No.: 105053-20112. The system of claim 8, wherein the controller is further programmed to reintegrate fluid particles reversed back through the entrance of the conduit during the reverse flow when said fluid particles reenter the conduit during a subsequent forward flow.

13. The system of claim 8, wherein the real-time movement of each of the fluid particles between the entrance of the conduit and an exit of the conduit is determined by tracking a movement of each of the fluid particles using a deque.

14. The system of claim 8, wherein the fluid comprises urine and the analyte measurement comprises urinary oxygen partial pressure.1632320064.4

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