Automated epidural loss of resistance detection system

Abstract

Various techniques related to an injection system are disclosed. Some example embodiments include a method of inserting a needle into a targeted location for administering an injection. The method can include: attaching an injection system to a needle; placing a tip of the needle at a location where an injection into a tissue is to be performed; causing the tip of the needle to advance into one or more layers of the tissue; and providing a flow rate reading or the pressure reading at one or more times as the tip advances into the one or more layers to enable a determination as to whether the tip has reached the targeted location.

Description

PCT Patent Application 009062.8556.WOOOAUTOMATED EPIDURAL LOSS OF RESISTANCE DETECTION SYSTEMCROSS-REFERENCE TO RELATED APPLICATION

[0001] This patent document claims priority to and benefits of U.S. Provisional Application 63 / 697,964, entitled “AUTOMATED EPIDURAL LOSS OF RESISTANCE DETECTION SYSTEM,” and filed on September 23, 2024. The entire content of the above noted patent application is incorporated by reference as part of the disclosure of this patent document.TECHNICAL FIELD

[0002] The present patent document relates to systems and methods that can facilitate finding an epidural space in a body of a patient during an epidural injection to the patient.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] FIG. 1 shows a schematic of an example order of tissues that a needle may follow to reach an epidural space in accordance with some disclosed embodiments.

[0004] FIG. 2 shows an annotated schematic of an exterior of an example embodiment based on the disclosed technology.

[0005] FIG. 3 shows an annotated image of an exterior of an example embodiment based on the disclosed technology.

[0006] FIG. 4 shows an annotated schematic of an interior of an example embodiment based on the disclosed technology.

[0007] FIG. 5 shows an annotated image of an interior of an example embodiment based on the disclosed technology.

[0008] FIG. 6 shows an annotated schematic showing example plumbing connections to an exterior of an example plumbing system based on the disclosed technology.

[0009] FIG. 7 shows a diagram of an example core connection of the plumbing system shown in FIG. 6.

[0010] FIG. 8 shows a schematic of an example printed circuit board (PCB) layout according to an embodiment based on the disclosed technology.

[0011] FIG. 9 shows a circuit schematic of an example embodiment based on the disclosed technology.1009062.8556. WOOO\183747782.1PCT Patent Application009062.8556.WD00

[0012] FIG. 10 shows an annotated image of an epidural simulator that can be implemented with some example embodiments based on the disclosed technology.

[0013] FIG. 11 shows example data obtained from a study performed in accordance with disclosed techniques.

[0014] FIG. 12 shows example calibration curves and equations from calibration testing of example embodiments based on the disclosed technology.

[0015] FIG. 13 shows a flow chart of an example method based on the disclosed technology.DETAILED DESCRIPTION

[0016] Epidural injections are administered by medical practitioners to patients to provide anesthesia during medical procedures, or relief from chronic pain. These injections involve inserting an epidural needle attached to a syringe filled with saline through a tissue of a patient until the epidural space is reached. The medical practitioners determine when the epidural space has been reached by using the “loss of resistance” (LOR) technique, which requires the medical practitioners to tap the syringe plunger as they advance the needle into the tissue until the plunger can be fully pressed. However, this technique relies heavily on the intuitions and experiences of the medical practitioner and therefore can be imprecise. In recognition of these challenges, an example system as disclosed in this document may replace a syringe and attach to a standard epidural needle for injecting into the spinal region. In some embodiments, the system includes two pressure sensors and a piezoelectric pump to pump saline through the needle and measure the pressure drop in the system as the needle advances through the different layers of the body (e.g., back) of the patient. The system can accurately detect a change in flow rate when the needle tip moves from, for example, a dense silicone region to an inner cavity that includes water. This monitoring epidural needle system, which provides quantitative flow rate measurements, can also be used to help medical students learn the feel of reaching the epidural space, and it may improve the success rate of epidural injections.

[0017] An epidural injection is a common medical procedure that is widely used by medical practitioners for treating body pain, for example, neck and back pain. The injection involves inserting a needle into the epidural space which is the potential space between the ligamentum flavum (a thick elastic ligament) and the dura mater (the tissue that protects the spinal cord and nerve roots). Medication such as steroids and local anesthetic are delivered into this area to help reduce2009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO inflammation and pain. This is commonly used, for example, for women during labor and for postoperative abdominal surgeries. Accurately locating the epidural space is extremely important and misjudging the depth can result in complications such as nerve damage or incomplete pain relief. The current technique used by doctors to identify the epidural space is called the LOR method. To perform this procedure, the syringe is initially filled with a portion of either saline or water. The administrator will simultaneously insert the needle and press on the syringe plunger to test the resistance of outward flow as the epidural needle advances through different tissue layers. In a layer with high resistance, such as the ligamentum flavum, almost no fluid may flow from the needle tip. Once the needle passes through this high resistance layer and enters the epidural space, there is a large pressure drop that indicates the loss of resistance on the needle tip, and fluid begins to flow. As shown in FIG. 1, an example order of tissues that a needle follows to reach the epidural space is skin, subcutaneous tissue, supraspinous and interspinous ligaments, ligamentum flavum, epidural space. In some examples, the ligamentum flavum is the final layer protecting the epidural space and is a thick and strong ligament made of elastic fibers. It has the largest resistance against needle insertion. As the needle punctures into the epidural space, a significant LOR can be felt as fluid is suddenly able to flow from the needle tip, which signals to the doctor that the epidural space has been reached. This method relies heavily on the tactile sense and intuition of the administrator which can be challenging and dangerous.

[0018] Various embodiments disclosed herein relate to finding an epidural space in a body of a patient during an epidural injection to the patient.

[0019] Various embodiments disclosed herein relate to an injection system or apparatus attachable to a needle.

[0020] In one aspect, an injection system attachable to a needle is disclosed. The injection system comprises: a housing; a reservoir; a tubing system comprising: an inlet coupled to the reservoir, and an outlet configured to be coupled to one end of the needle; a first pressure sensor coupled to the tubing system; a second pressure sensor coupled to the tubing system; and a piezoelectric pump coupled to the inlet and the outlet, wherein: the first pressure sensor, the second pressure sensor, and the piezoelectric pump are disposed within the housing, the piezoelectric pump is configured to cause a fluid from the reservoir to be drawn into the inlet to allow the fluid to flow through the tubing system and into the needle, the first pressure sensor is configured to provide a first measurement associated with a pressure difference between the fluid in the tubing system and an3009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO environment, the second pressure sensor is configured to provide a second measurement associated with a pressure difference of the fluid across a known length of the tubing system.

[0021] In another aspect, a method of inserting a needle into a targeted location for administering an injection of a fluid, comprising: attaching an injection system to a needle, wherein the injection system comprises: a display, a tubing system comprising: an inlet coupled to a reservoir, and an outlet configured to be coupled to one end of the needle, a first pressure sensor coupled to the tubing system, a second pressure sensor coupled to the tubing system, and a piezoelectric pump coupled to the inlet and the outlet, wherein: the piezoelectric pump is configured to cause a fluid from the reservoir to be drawn into the inlet to allow the fluid to flow through the tubing system and into the needle, the first pressure sensor is configured to provide a first measurement associated with a pressure difference between the fluid in the tubing system and an environment, the second pressure sensor is configured to provide a second measurement associated with a pressure difference of the fluid across a known length of the tubing system, and the display is configured to provide a flow rate reading or a pressure reading based on the first measurement or the second measurement; placing a tip of the needle at a location where an injection into a tissue is to be performed; causing the tip of the needle to advance into one or more layers of the tissue; and providing the flow rate reading or the pressure reading on the display at one or more times as the tip advances into the one or more layers to enable a determination as to whether the tip has reached the targeted location, wherein the determination is based on the flow rate reading or the pressure reading at the one or more times.

[0022] The disclosed embodiments relate in-part to a system that can facilitate locating the epidural space reliably and more accurately. In some embodiments, the disclosed system may be attached to an epidural needle which can accurately measure the resistance of the tissue layers the needle is penetrating. Upon entering into the epidural space, the device may notify the medical practitioner through a display (e.g., a live plot of the resistance or an LED signal). The device may utilize sensors and software detection that eliminates the uncertainty and intuition that the existing LOR technique relies on.

[0023] Existing technologies for entering an epidural space include mechanical devices which rely on pressure sensing to confirm the needle placement in the epidural space and on a feedback loop to control a motor that drives the injection mechanism of the device. The disclosed embodiments provide advantages over the existing technologies in several ways. For example, some disclosed4009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO embodiments are easy to attach to an existing epidural needle, as well as easy to disconnect so that the needle can be changed in between uses. Some disclosed embodiments detect the different resistances the needle feels through each tissue layer. Some disclosed embodiments include a screen or light that can notify the medical practitioner once the needle enters the epidural space. In some p embodiments, the layers may be characterized by a “resistance metric” defined as R = - where “P” is the pressure applied by the pump and “Q” is the measured flow rate.

[0024] Some disclosed embodiments relate to an instrumented epidural injector system that offers several advantages for public health and safety. Some advantages include improving epidural injection success rates and ease of use, which can have a broader societal impact extending beyond immediate clinical applications. Specifically, it could optimize the medical training process to reduce the costs in time and materials and conversely increase productivity for medical facilities, or possibly inspiring other medical procedures to become automated.

[0025] Some disclosed embodiments relate to an automated needle injector system that provides precise and consistent needle placements, reducing the risk of complications and increasing the success rate of epidural injections. Since the system is designed to be both precise and user- friendly for medical professionals, the injection procedure is optimized, reducing injection duration, which also reduces the discomfort of the patient. The features and qualities that the automated epidural injector system possesses allows it to be integrated into current medical training practices. The system can enhance the learning experience of medical students, helping them become familiar with the LOR feeling. This helps students develop the skills and confidence they need before going into the field, which ultimately improves patient outcomes in the long run. In addition, the system can be used at hospitals across the world to help medical practitioners reduce epidural failure rate. Additionally, the disclosed technology can be used for epidural electrical simulation systems to assist patients dealing with spinal cord injuries.

[0026] In one aspect, an instrumented epidural injector system is disclosed. The disclosed system may replace the tactile feel the medical practitioners develop with a quantitative measurement. The system provides a visual and / or auditory signal when the medical practitioner has reached the appropriate place with the needle to allow for more accurate and precise needle placement. This can increase procedural efficiency and reduce complications. The disclosed technology may facilitate the practice of finding the epidural space during routine epidural injections by building on the LOR5009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO technique. It uses the change in pressure across a known length of tubing to determine if fluid is flowing through the needle tip (using pressure supplied by the device’s pump). Whether the fluid is stagnant or flowing may indicate if the needle tip is in a bodily tissue of high resistance (e.g., ligamentum flavum) or low resistance (e.g., the epidural space), respectively. In some embodiments, the resistance to flow of the bodily medium indicates to the medical practitioner if the needle has reached the epidural space. The disclosed system may use different physical data to determine when the epidural space has been reached by the needle tip. In some embodiments, it may rely on a pump and pressure sensor as opposed to the haptic feedback that clinicians develop as they practice epidural injections. In some embodiments, it may mimic the change in resistance to flow (which the medical practitioners may refer to as the LOR technique). In some embodiments, the disclosed system may measure the pressure in the tubing system that is generated by the fluidic pump.

[0027] In some embodiments, the disclosed system relies on a piezoelectric pump to pull liquid (e.g., water, saline, etc.) from a reservoir into the tubing system. The system includes two differential pressure sensors on a Printed Circuit Board (PCB) that measure: a) the pressure difference between the tubing lumen and the ambient environment and b) the pressure difference across a known length of tubing. The first pressure reading is to simply determine the pressure in the tubing while the second pressure reading is to understand the flowrate across the known length of tubing (which may be obtained from calibrating the device to verify the linear relationship between volumetric flowrates and pressure difference). In some embodiments, the pressure generated inside the tubing may be sufficient to identify when the epidural space has been reached. In some embodiments, the PCB contains some basic signal filtering to remove high-frequency noise from the pressure readings. In some embodiments, the signals can be amplified to a measurable voltage for reading by a controller board, for example, the Arduino Nano. The controller board, for example, the Arduino Nano, then displays the pressure reading on a display for the clinician to read and interpret.

[0028] In some embodiments, the disclosed system allows for integration with current epidural injection kits and minimizes the addition of extra components (e.g., use inlet and outlet fittings sized for existing tubing). In some embodiments, the disclosed system includes a pressure relief system to set a maximum allowable pressure in the device plumbing (avoid possibly dangerous pressure spikes). In some embodiments, the disclosed system has a small size so that it can be held in series with the standard needle (as opposed to a bench-top device supplying fluid to a needle via extension tubing).6009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOOIn some embodiments, the disclosed system maintains standard procedure sterility with low minimal cleaning requirements between uses. In some embodiments, the disclosed system may include a handheld version of the system that may collect consistent measurements, even if the system is not completely stable, such as when the medical practitioner is moving the device a little.

[0029] In another aspect, a method that automatically detects epidural LOR is disclosed. In some embodiments, the method may include pumping liquid (e.g., water, saline, etc.) through the needle and measuring the pressure drop in the system as the needle advances through the different layers of a body (e.g., the back) of a patient. The method further includes, when the measured pressure drops below a threshold, notifying a medical practitioner that the needle is in the epidural space.

[0030] In yet another aspect, a system that automatically detects epidural LOR is disclosed. In some embodiments, the system is a 3D-printed tabletop device with a tubing, piezoelectric pump, and controller system that can (1) attach to existing medical equipment (e.g., Tuohy needle, saline bags), (2) automatically dispense saline through the needle without a syringe, (3) precisely detect small pressure differences within 1 psi and therefore detect varying resistances of tissue to the needle, and (4) provide live-feed readings of flow rate measurements as the needle advances through several layers of tissue. In some embodiments, the 3D-printed device is powered with DC wall power and can be turned on / off using the main power button switch, while the pump can be independently turned on / off with a separate button switch to provide more control over fluid flow. FIG. 2 shows an annotated schematic of an exterior of an example embodiment of the system. FIG. 3 shows an annotated image of an exterior of an example embodiment of the system. In some embodiments, the 3D-printed housing protects the electronic components of the precise pressure detection system of the device from corrosion and contamination, allowing tubes to connect to the pressure sensors externally through dedicated outlets in the housing walls. FIG. 4 shows an annotated schematic of an interior of an example embodiment of the system. FIG. 5 shows an annotated image of an interior of an example embodiment of the system.

[0031] Some disclosed embodiments relate to a plumbing system that can include inlet tubing for a saline reservoir, a piezoelectric pump, a PCB including two differential pressure sensors, and outlet tubing fitted with a luer lock for connecting to a standard epidural Tuohy needle. In an example embodiment, liquid (e.g., saline) is drawn into the main inlet tubing of the system by the pump and then travels across the pressure sensor system, to the main outlet tubing, and finally out of the needle. FIG. 6 shows an annotated schematic showing example plumbing connections to an exterior of an7009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO example plumbing system. FIG. 7 shows a general diagram of an example core connection of the plumbing system shown in FIG. 6.

[0032] In some embodiments, the pump is programmed to output a steady flow rate (e.g., 2 mL / min). In some embodiments, the pump and the volumetric flow rate that it outputs can be controlled using pulse width modulation (PWM) code. In some embodiments, the PWM control may not be necessary for accurate identification of the epidural space. In some embodiments, the pump runs at a fixed flow rate.

[0033] Some disclosed embodiments related to an electronics system. FIG. 8 shows a schematic of an example PCB design of a disclosed electronics system, with the main electronic component labeled in FIG. 8. In some embodiments, the disclosed system relies on measuring the pressure drop in the system to detect when the epidural space has been reached. In some embodiments, the system contains a piezoelectric pump that can draw saline from an inlet reservoir at a low and steady nominal flow rate (e.g., 2 mL / min), as well as a pressure-sensor and tubing system comprising two differential board mount pressure sensors as shown in FIG. 8. In some embodiments, one of the pressure sensors can measure a pressure difference (e.g., up to 15 psi) to determine the gauge pressure in the tubing and the other can measure another pressure difference (e.g., up to 1 psi). In some embodiments, the other one of the two pressure sensors is used to determine the differential pressure across a given length of tubing. This differential pressure can be used to obtain the flow rate of saline through the epidural needle. In some embodiments, the PCB has two pressure sensors. In some embodiments, the PCB has only one pressure sensors as the volumetric flow rate may be a sufficient metric for detecting the epidural space. In some embodiments, the pressure detection system contains low-cost components, and is controlled using a custom PCB. In some embodiments, the board is powered via a standard DC barrel jack connector that can draw power from the wall. In some embodiments, power from this connector is fed directly into an Arduino Nano’s “VIN” pin which reduces the voltage to a 5V output to control all the components on the board. Each pressure sensor may contain a signal conditioning circuit which is used for amplifying and filtering small-scale pressure difference signals. In some embodiments, the signal conditioning circuits include an instrumental amplifier, operational amplifier, and several resistors and capacitors. In some embodiments, each component on the PCB may require 5V power and ground connections and may include a decoupling capacitor (e.g., 1 pF) to reduce signal noise. In some embodiments, the PCB provides connections to a display (e.g., 2x16 LCD screen) and the pump (FIG. 9). FIG. 9 shows a circuit schematic of example electrical8009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WG00 components including the PCB, display, and pump. The display may be used to display the most recent flow rate value from one of the pressure sensors (e.g., the 1 psi pressure sensor) using I2C serial communication. In some embodiments, the pump may be powered by the 5 V power and ground lines of the PCB and controlled by a pin of the Arduino Nano which writes a digital “HIGH” or “LOW” value to turn the pump off and on, respectively.

[0034] Performance of an example system based on the disclosed technology was evaluated using an epidural training simulator that included a ballistic gel block surrounding a silicone tubing (0.5” outer diameter, 0.4” inner diameter) containing water inside. FIG. 10 shows an annotated image of the example epidural simulator used for training. In some embodiments, the needle can be inserted slowly through the ballistic gel block and the silicone tubing into the core filled with water. In an example demonstration, the total time for inserting through the ballistic gel and tube wall was about 11 seconds while the time in which the needle was within the tubing (i.e., “epidural space”) was about 10 seconds. In the example demonstration, when inserting the needle through the ballistic gel and tubing wall, the flow rate readings were 1.02 ± 0.84 [pL / s], The flow rate readings following puncture of the inner tubing wall (i.e., entry into the “epidural space”) were 29.7 ± 5.3 [pL / s], The difference in mean flow rate between the ballistic gel / tube wall and the simulated epidural space was statistically significant at p « 0.001.

[0035] These example results indicate that the disclosed device has a high probability of accurately identifying when the needle tip has moved from a region of high resistance to flow to a region of low resistance where flow increases. FIG. 11 shows example data obtained in the example test described above. Specifically, FIG. 11 shows resultant flow rate and pressure plots from the example testing method. As shown in FIG. 11, the flow rate drops once the needle is inserted into the ballistic gel and the pressure within the tubing builds during this time. Once the needle punctures into the simulated epidural space, the flow rate spikes and levels out while the pressure inside drops.

[0036] The example data shown in FIG. 11 for flow rate is the result of smoothing using a moving mean of the last 10 values recorded. This reduces the magnitude of the plotted pressure spike which may truly have been higher than what is shown in FIG. 11.

[0037] Some disclosed embodiments included a pump which may be configured to pull liquid from a reservoir into a tubing system in accordance with some disclosed techniques. Table I shows some example features of pumps that can be implemented with disclosed embodiments.9009062.8556. WO00\l 83747782.1PCT Patent Application 009062.8556.WOOOTable I: Example features of a Pump

[0038] In some embodiments, the pump is powerful enough to generate fluid flow within the plumbing system. In some embodiments, the pump supplies a fluid flow within an allowable flow rate range (e.g., 0.5-5 mL / min). In some embodiments, the pump can connect to plastic tubing using connectors that are easily available by suppliers such as McMaster-Carr.

[0039] In some disclosed systems, the Takasago pump of Table I employed as it allows for PWM control of the pump to reduce the flow rate when the epidural space has been reached. In some embodiments, the Takasago pump can be integrated smoothly with an Arduino because it only needs a driver module that provides 5 VDC for power. In some embodiments, the Takasago pump can supply a maximum volumetric flow rate of, for example, 3 mL / min. In some embodiments, Isopropyl alcohol can be pumped through the Takasago pump to sanitize it and ensure sterility.

[0040] Some disclosed embodiments include pressure sensors. Table II shows example features of pressure sensors than can be implemented in some disclosed embodiments.Table II: Example features of Pressure Sensors10009062.8556. WO00\l 83747782.1PCT Patent Application009062.8556.WOOO

[0041] In some embodiments, the pressure sensors may precisely measure the pressure drop across two points in a plumbing system based on the disclosed technology. Measurements can be collected at two points in the system by integrating two individual pressure sensors.

[0042] In some embodiments, between uses, the saline may be expelled from the tubing, and the tubing is then flushed with air. In some embodiments, the sensor / s can withstand being flushed with air without needing to be re-calibrated before saline is pumped through it during the next use. In some examples, flushing the system with air between uses may minimally affect pressure readings.

[0043] In some embodiments, the response time may be low (e.g., <10 ms). If the sensor requires some amount of warm-up time before measurements, then this period of warm-up time may not exceed a threshold (e.g., 5 minutes). In some embodiment, the pressure sensors may not be larger than a threshold (e.g., 0.5 ft3). In some embodiments, the pressure sensors may be small enough to fit within the size constraint of the overall system (e.g., 1.0 ft3).

[0044] In an example embodiment, at least one of the pressure sensors was a Honeywell 26PCXXSMT, which may cost $100 per sensor and promises accuracy with 0.5%. These sensors could be easily integrated with the PCB. There are metal prongs on the sensor which allow for easy soldering to an electronics board. These sensors are also small (approximately 1 cm3), so they can easily fit within the size requirements of the system.11009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO

[0045] Some example embodiments include a controller board. Table III shows some example features of various controller boards that can be implemented with some disclosed embodiments.Table III: Example features of Controller Board

[0046] In some embodiments, the controller board may contain a microprocessor to handle calculations using the output from two pressure sensors. In some embodiments, the controller board may operate a display (e.g., an LCD screen) that displays live pressure readings to a user. In some embodiments, the controller board may connect with an external computer or laptop to easily export data measurements from controller board during calibration. In some embodiments, the controller board may interface with an Arduino Nano, which may be microcontroller for the electronics components.

[0047] In some embodiments, the controller board includes a customized PCB that allows a specific circuit to be integrated into the system. In some embodiments, an Arduino Nano may be mounted onto the PCB to serve as the microcontroller for the electronics. In some embodiments, the PCB allows for a permanent fixture of all components necessary for signal conditioning to amplify the pressure sensor readings to voltages measurable by the Arduino Nano.Example Fabrication Methods

[0048] Some disclosed embodiments may be fabricated, at least in part, using techniques disclosed herein. In one example fabrication method, individual resistors, capacitors and pressure sensors may be soldered directly onto a PCB board. Sockets for the instrumental and operational12009062.8556. WOOO\183747782.1PCT Patent Application009062.8556.WOOO amplifiers may be soldered into the board so that these components could be swapped out easily if damaged. In some embodiments, the system may not include holes to solder wires for buttons to control device power, so the live trace from the barrel jack to the Arduino VIN pin is cut, allowing for the wires to be soldered directly onto the PCB that would connect to the button to allow for the device to be off even when plugged in. Female header pins may be soldered onto the PCB for connection to the LCD screen and piezoelectric pump. In some embodiments, the power cable of a pump may be cut and each end may be soldered to a button to all the pump to be turned on and off. Some disclosed embodiments may include 3D printed components. Tough Polyvinyl alcohol (PVA) filament may be used as the material for the print. The PCB and LCD screen may be secured to the device using M3 screws and nuts. In some example embodiments, the lid of a device housing may be secured to the bottom shell of the device housing also using M3 screws and nuts. In some embodiments, when press-fitting two different diameter tubing together, there may be at least a slight (e g., 1 cm) overlap in the two tubes to ensure a secure connection.

[0049] In an example study of a device based on the disclosed technology, to calculate the expected volumetric flow rate and pressure drop for theoretical predictions, it was assumed that there is no head loss from the fittings, and there is no significant pressure losses from the bubbles inside the tubing. Further, water was used for the test. Both saline and water are incompressible, are Newtonian fluids, and have similar densities, so it is assumed that both fluids behave similarly and that physical parameters for saline could be used in the analysis. For this analysis, it was assumed that the density of saline is 1 g / cm3, and the dynamic viscosity of saline is assumed to be about 9.3 I * 104Pascal seconds.

[0050] To determine how to model the flow for the theoretical predictions of pressure drop in the device, the Reynolds number of the flow that is output from the pump was determined. The diameter of the tubing connected to the outlet of the pump was 0.79 mm. The system used for testing in this stage of the design process included a different pump that has a high flow rate of 30 mL / min. The velocity of the flow may be determined using the continuity equation, as shown below in Equation 2. In this equation, Q is the expected volume flow rate, A is the cross-sectional area of the tubing, and V is the velocity of the fluid. It was determined that the velocity of the flow was about 102 cm / s.Q = VA (2)13009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO

[0051] The Reynolds number for saline flowing through the tubing was calculated using Equation 3. In this equation, p is the fluid density, V is the velocity of the fluid, D is the diameter of the tubing, and p is the dynamic viscosity of the fluid. It is determined that the Reynolds number is about 866, indicating that the flow through the tube is laminar.

[0052] In the example device, the flow is laminar, the fluid has a constant velocity, the tubing has a constant cross-sectional area, the length of the tubing is greater than the diameter of the tubing, and the flow is assumed to behave as a Poiseuille flow. This type of flow is described by the Hagen- Poiseuille equation, shown below in Equation 4. In this equation, L is the length of the tubing. The Hagen-Poiseuille equation expresses a relationship between the pressure drop and volumetric flow rate of fluid flowing through a tube. Since the volumetric flow rate from the tip of the needle changes as it passes through different tissue layers with different resistances, the Hagen-Poiseuille equation provides a way to quantify the pressure drop associated with passing through one layer to the next.

[0053] The pressure sensors measure changes in voltage, and these voltage measurements correspond to changes in pressure. A manometer may be used to collect pressure measurements and calibrate the sensors. Changes in the pressure applied to the water column may cause the fluid height within the manometer to change. These pressure changes may be measured in units of centimeters of water, which can be directly converted to pressure in Pascals. During calibration, the voltage output from the pressure sensors may be measured as the pressure is varied, and the water column in the manometer changes. The pressure measurement may be determined from the manometer reading, and the corresponding voltage measurement may be recorded. Once the pressure reading from the manometer and voltage measurements may be collected for different applied pressures, a calibration curve can be plotted. This example calibration curve shows the relationship between the change in voltage and the pressure drop. This results in a linear equation that described the calibration curve, and this equation may be used to convert the voltage measurements from the sensor to pressure in Pascals.

[0054] Using Equation 4, it can be predicted that at a saline flow rate of 30 mL / min, the pressure drop across a 20 cm long piece of PVC tubing with an inner diameter of 0.16 cm (0.063 inches) would be 690 Pa (0.1 psi). The example experimental pressure drop measured using the calibration equation14009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO from the calibration curve reveals a drop of about 1,310 Pa (0.19 psi) for the physical setup. It may be determined that the theoretical pressure drop across the two points may appear to be half that of the pressure difference measured by the pressure sensor. This could be due to the presence of bubbles in the small tubing resulting in the formation of a meniscus which induces a pressure drop. There could also be additional sources of pressure loss due to the use of 90° tee fittings. In some embodiments, the circuit for the device is built on a breadboard, and the wires and electronic components are therefore not permanently fixed in a specific position. This may accordingly lead to additional noise in the calibration measurements, which may have contributed to the discrepancies in the measured pressure drop.

[0055] In another examples study, one performance metric for a disclosed device was that it needed to be able to precisely detect when the needle entered the epidural space. During an epidural injection, the needle passes through skin, fat, muscle, and the ligamentum flavum before it reaches the epidural space. Each tissue layer differs enough such that the volumetric flow rate of saline from the needle tip would change as the needle passes through each layer. The Hagen-Poiseuille equation may provide a good approximation to model the fluid flow in the device and calculate the pressure drop. In some embodiments, the system may rely on the pressure sensors making precise voltage measurements in order determine precise pressure drop values. FIG. 12 shows example calibration curves and equations from calibration testing for pressure sensors connected to a breadboard circuit (FIG. 12, left) and a PCB (FIG. 12, right), where FIG. 12 (left) and FIG. 12 (right) describe different example embodiments.

[0056] In some embodiments, when calibrating the pressure sensors, there is a linear relationship between the voltage measured by the pressure sensors and the pressure reading from the manometer water level. In some embodiments, when the pressure sensors are attached to the circuit on the breadboard, the relationship is not linear, as shown in FIG. 12 (left), This may be because of noise in the circuit, which was initially built on a breadboard to allow for testing and modifying the circuit in the study. Any slight movements that caused the connections between a wire or electronic component to shift may lead to significant amounts of noise. As shown in FIG. 12 (right), in the example embodiment including a PCB, when the pressure sensors are attached to the PCB, a linear relationship between voltage and pressure measurements is achieved.15009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO

[0057] Some disclosed embodiments may have a tabletop design. In an example, a disclosed device may rest on a flat surface near the patient and the practitioner during an epidural procedure. This may be done to ensure that the main components of the device would be stable when the device is in use, which reduces noise in the pressure measurements. Additionally, this is different from existing technologies for epidural injections which commonly use a syringe. Some disclosed embodiments may be handheld to make it easy for the practitioner to use. In one example, when the disclosed system is handheld, the practitioner may not be limited to be near a surface on which to rest the system. In some embodiments, the size of the disclosed system is small enough to be handheld. In some embodiments, the pressure sensors are not sensitive to vibrations. In some embodiments, the components of the hand-held system are kept stable when the hand-held system is collecting measurements. In some embodiments, using an excessive length of tubing to induce a measurable pressure drop is avoided. For example, pneumatic restricting mechanisms may be implemented.

[0058] Some disclosed embodiments may be made more compact by changing the layout of the electronic components. In some embodiments, there may be no use of a pressure sensor for detecting the pressure inside the tubing to accurately identify the epidural space as the flow rate is a key indicator of which tissue the tip is in. In some embodiments, the pressure sensor and its signal conditioning circuit may be removed to greatly reduce the footprint of the PCB.

[0059] In some embodiments, the disclosed system may be connected to a power source (e.g., wall outlet) in order to be powered.

[0060] Some disclosed embodiments draw little power and a battery may be implemented as the power source. This can allow for isolation of the device (e.g., isolated from a wall outlet) and allow a clinician to move freely with the device.

[0061] Some disclosed embodiments include components that can be sterilized, for example, by flushing isopropyl alcohol through the pump and the tubing. Some disclosed embodiments may be partially or completely disposable. Some disclosed epidural injection techniques may use a disposable syringe.

[0062] In some embodiments, automation in the control of the device can be implemented for better control of the flow rate spike once the epidural space is reached. Such control in the circuit16009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO could safeguard the patient from the rapid increases in flow which may cause some damaging effects to the tissues adjacent to the epidural space.

[0063] In some embodiments, to ensure safety of the patient in the event of any potential malfunctioning of the system, there are mechanisms in place so that the practitioner that is administering the injection still has complete control over the injection and still partially relies on their intuition to find the epidural space. In some embodiments, the instrumented epidural needle injector system is automated. In some embodiments, the instrumented epidural needle injector system is not automated, and is not meant to replace the medical practitioner and the intuition they acquire as they are taught to administer epidural injections. Instead, it provides a way for them to verify the empirical estimate that they will make when they administer the injection using the loss of resistance technique.

[0064] In some embodiments, the disclosed system includes a PCB, where the connections in the circuit are permanently set, and the electronic components are soldered into place, resulting in no noise due to components or wires shifting. In some embodiments, the measurements are very precise when using the PCB, and the system is sensitive enough to measure the different tissue layers just based on the volumetric flow rate in the system.

[0065] In some embodiments, the disclosed system may detect a change in flow rate between the ballistic gel and a simulated epidural space.

[0066] In some embodiments, the flow rate is used as a metric that clinicians rely on to distinguish which layer of the back the needle tip is in.

[0067] In some embodiments, pump power is controlled when the epidural space is reached. Controlling the pump power could prevent excess deposition of saline into the epidural space and could introduce further complications as pressure in the epidural space builds.

[0068] FIG. 13 shows a flow chart of an example method 1300 of inserting a needle into a targeted location for administering an injection of a fluid according to an embodiment of the disclosed technology. At step 1310, the method 1300 comprises: attaching an injection system to a needle. In some implementations, the injection system comprises: a display, a printed circuit board (PCB), a tubing system comprising: an inlet coupled to a reservoir, and an outlet configured to be coupled to one end of the needle, a first pressure sensor coupled to the tubing system and disposed on the PCB,17009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO a second pressure sensor coupled to the tubing system and disposed on the PCB, and a piezoelectric pump coupled to the inlet and the outlet. In some implementations, the first pressure sensor is configured to measure a pressure difference between a tubing lumen of the tubing system and an environment, the second pressure sensor is configured to measure a pressure difference across a known length of the tubing system, the piezoelectric pump is configured to cause a fluid from the reservoir to be drawn into the inlet to allow the fluid to flow through the tubing system, the first pressure sensor, and the second pressure sensor, and into the needle, and the display is configured to provide a flow rate reading or a pressure reading based on a measurement by the first pressure sensor or the second pressure sensor. At step 1320, the method 1300 comprises: placing a tip of the needle at a location where an injection into a tissue is to be performed. At step 1330, the method 1300 comprises: causing the tip of the needle to advance into one or more layers of the tissue. At step 1340, the method 1300 comprises: providing the flow rate reading or the pressure reading on the display at one or more times as the tip advances into the one or more layers to enable a determination as to whether the tip has reached the targeted location. In some implementations, the determination is based on the flow rate reading or the pressure reading at the one or more times.

[0069] Embodiments of the disclosed technology support inter alia the following technical solutions.

[0070] 1. An injection system attachable to a needle, comprising: a housing; a reservoir; a tubing system comprising: an inlet coupled to the reservoir, and an outlet configured to be coupled to one end of the needle; a first pressure sensor coupled to the tubing system; a second pressure sensor coupled to the tubing system; and a piezoelectric pump coupled to the inlet and the outlet, wherein: the first pressure sensor, the second pressure sensor, and the piezoelectric pump are disposed within the housing, the piezoelectric pump is configured to cause a fluid from the reservoir to be drawn into the inlet to allow the fluid to flow through the tubing system and into the needle, the first pressure sensor is configured to provide a first measurement associated with a pressure difference between the fluid in the tubing system and an environment, the second pressure sensor is configured to provide a second measurement associated with a pressure difference of the fluid across a known length of the tubing system.18009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO

[0071] 2. The injection system of solution 1, comprising a fitting coupled to the outlet and the one end of the needle, wherein the fluid is allowed to flow through the outlet and out of a tip of the needle based on a configuration of the fitting.

[0072] 3. The injection system of solution 1, wherein the housing is a multi-walled housing comprising a wall having multiple holes, wherein the first pressure sensor is coupled to the tubing system via a first hole in the wall, wherein the second pressure sensor is coupled to the tubing system via a second hole and a third hole in the wall.

[0073] 4. The injection system of solution 1, comprising a controller coupled to the piezoelectric pump and disposed within the housing, wherein the controller is configured to output one or more control signals to control an operation of the piezoelectric pump.

[0074] 5. The injection system of solution 4, wherein the operation corresponds to activation or deactivation of the piezoelectric pump.

[0075] 6. The injection system of solution 4, wherein at least one of the one or more control signals causes the piezoelectric pump to cause the fluid from the reservoir to be drawn into the inlet at a predetermined flow rate.

[0076] 7. The injection system of solution 4, comprising a printed circuit board (PCB), wherein the first pressure sensor, the second pressure sensor, and the controller are disposed on the PCB.

[0077] 8. The injection system of solution 1, comprising a display configured to provide a flow rate reading, wherein the flow rate reading is based on the second measurement.

[0078] 9. The injection system of solution 7, wherein the first measurement is used to determine a pressure in the tubing system.

[0079] 10. The injection system of solution 9, wherein a second measurement is used to determine a flow rate across the known length of the tubing system.

[0080] 11. The injection system of solution 10, wherein the PCB comprises a signal conditioning circuit, wherein the signal conditioning circuit is configured to provide a filtered signal by removing high-frequency noise from the first measurement or the second measurement.

[0081] 12. The injection system of solution 11, wherein the signal conditioning circuit comprises an amplifier configured to amplify the filtered signal to a measurable voltage.19009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO

[0082] 13. The injection system of solution 12, wherein the measurable voltage is used to obtain a pressure reading.

[0083] 14. The injection system of solution 13, wherein the pressure reading is provided to a screen for display.

[0084] 15. The injection system of solution 1, where the injection system is completely or partially disposable.

[0085] 16. A method of inserting a needle into a targeted location for administering an injection of a fluid, comprising: attaching an injection system to a needle, wherein the injection system comprises: a display, a tubing system comprising: an inlet coupled to a reservoir, and an outlet configured to be coupled to one end of the needle, a first pressure sensor coupled to the tubing system, a second pressure sensor coupled to the tubing system, and a piezoelectric pump coupled to the inlet and the outlet, wherein: the piezoelectric pump is configured to cause a fluid from the reservoir to be drawn into the inlet to allow the fluid to flow through the tubing system and into the needle, the first pressure sensor is configured to provide a first measurement associated with a pressure difference between the fluid in the tubing system and an environment, the second pressure sensor is configured to provide a second measurement associated with a pressure difference of the fluid across a known length of the tubing system, and the display is configured to provide a flow rate reading or a pressure reading based on the first measurement or the second measurement; placing a tip of the needle at a location where an injection into a tissue is to be performed; causing the tip of the needle to advance into one or more layers of the tissue; and providing the flow rate reading or the pressure reading on the display at one or more times as the tip advances into the one or more layers to enable a determination as to whether the tip has reached the targeted location, wherein the determination is based on the flow rate reading or the pressure reading at the one or more times.

[0086] 17. The method of solution 16, comprising: operating the injection system to cause the fluid to be dispensed through the tip and into the targeted location.

[0087] 18. The method of solution 16, wherein the injection system further comprises: a printed circuit board (PCB) comprising a signal conditioning circuit; a fitting coupled to the outlet and the one end of the needle, wherein: the fluid is allowed to flow through the outlet and out of the tip based on a configuration of the fitting, the first pressure sensor and the second pressure sensor are disposed20009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO on the PCB, the signal conditioning circuit is configured to provide a signal by removing high- frequency noise from the first measurement or the second measurement, and the signal conditioning circuit comprises an amplifier configured to amplify the signal to a measurable voltage.

[0088] 19. The method of solution 18, wherein the measurable voltage is used to obtain the flow rate reading or the pressure reading.

[0089] 20. The method of solution 16, wherein the targeted location is an epidural space in a back of a human body.

[0090] 21. An injection system to be attached to a needle, comprising: a reservoir; a tubing system; a pump configured to pull liquid from the reservoir into the tubing system; a first pressure sensor configured to measure a pressure difference between a tubing lumen and an ambient environment; and a printed circuit board (PCB), wherein the first pressure sensor is on the PCB.

[0091] 22. The system of solution 21, wherein the pump is a piezoelectric pump.

[0092] 23. The system of solution 21, further comprising a second pressure sensor configured to measure a pressure difference across a known length of tubing, wherein the second pressure sensor is on the PCB.

[0093] 24. The system of solution 23, wherein the first pressure sensor and the second pressure sensor are differential pressure sensors.

[0094] 25. The system of solution 23, wherein a first measurement from the first pressure sensor is used to determine a pressure in the tubing system.

[0095] 26. The system of solution 25, wherein a second measurement from the second pressure sensor is used to determine a flow rate across a known length of the tubing system.

[0096] 27. The system of solution 26, wherein the PCB comprises a signal filter configured to provide a signal by removing high-frequency noise from a pressure reading from the first measurement or the second measurement.

[0097] 28. The system of solution 27, wherein the PCB further comprises an amplifier configured to provide an amplified signal by amplifying the signal to a measurable voltage.

[0098] 29. The system of solution 28, wherein the amplifier is further configured to transmit the amplified signal to a display.21009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO

[0099] 30. The system of solution 29, wherein the display is configured to display the pressure reading based on the amplified signal for a medical practitioner to read and interpret.

[0100] Implementations of the subject matter and the functional operations described in this patent document can be implemented in various systems, digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Implementations of the subject matter described in this specification can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a tangible and non-transitory computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more of them. The term “data processing unit” or “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them.

[0101] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

[0102] The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be22009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0103] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random-access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of nonvolatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0104] While this patent document contains many specifics, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this patent document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0105] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments.23009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO

[0106] Only a few implementations and examples are described and other implementations, enhancements and variations can be made based on what is described and illustrated in this patent document.24009062.8556. WOOO\183747782.1

Claims

PCT Patent Application 009062.8556.WOOOWhat is claimed is:

1. An injection system attachable to a needle, comprising: a housing; a reservoir; a tubing system comprising: an inlet coupled to the reservoir, and an outlet configured to be coupled to one end of the needle; a first pressure sensor coupled to the tubing system; a second pressure sensor coupled to the tubing system; and a piezoelectric pump coupled to the inlet and the outlet, wherein: the first pressure sensor, the second pressure sensor, and the piezoelectric pump are disposed within the housing, the piezoelectric pump is configured to cause a fluid from the reservoir to be drawn into the inlet to allow the fluid to flow through the tubing system and into the needle, the first pressure sensor is configured to provide a first measurement associated with a pressure difference between the fluid in the tubing system and an environment, the second pressure sensor is configured to provide a second measurement associated with a pressure difference of the fluid across a known length of the tubing system.

2. The injection system of claim 1, comprising a fitting coupled to the outlet and the one end of the needle, wherein the fluid is allowed to flow through the outlet and out of a tip of the needle based on a configuration of the fitting.

3. The injection system of claim 1, wherein the housing is a multi-walled housing comprising a wall having multiple holes, wherein the first pressure sensor is coupled to the tubing system via a first hole in the wall, wherein the second pressure sensor is coupled to the tubing system via a second hole and a third hole in the wall.25009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO4. The injection system of claim 1, comprising a controller coupled to the piezoelectric pump and disposed within the housing, wherein the controller is configured to output one or more control signals to control an operation of the piezoelectric pump.

5. The injection system of claim 4, wherein the operation corresponds to activation or deactivation of the piezoelectric pump.

6. The injection system of claim 4, wherein at least one of the one or more control signals causes the piezoelectric pump to cause the fluid from the reservoir to be drawn into the inlet at a predetermined flow rate.

7. The injection system of claim 4, comprising a printed circuit board (PCB), wherein the first pressure sensor, the second pressure sensor, and the controller are disposed on the PCB.

8. The injection system of claim 1, comprising a display configured to provide a flow rate reading, wherein the flow rate reading is based on the second measurement.

9. The injection system of claim 7, wherein the first measurement is used to determine a pressure in the tubing system.

10. The injection system of claim 9, wherein the second measurement is used to determine a flow rate across the known length of the tubing system.

11. The injection system of claim 10, wherein the PCB comprises a signal conditioning circuit, wherein the signal conditioning circuit is configured to provide a filtered signal by removing high-frequency noise from the first measurement or the second measurement.

12. The injection system of claim 11, wherein the signal conditioning circuit comprises an amplifier configured to amplify the filtered signal to a measurable voltage.26009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO13. The injection system of claim 12, wherein the measurable voltage is used to obtain a pressure reading.

14. The injection system of claim 13, wherein the pressure reading is provided to a screen for display.

15. The injection system of claim 1, where the injection system is completely or partially disposable.

16. A method of inserting a needle into a targeted location for administering an injection of a fluid, comprising: attaching an injection system to a needle, wherein the injection system comprises: a display, a tubing system comprising: an inlet coupled to a reservoir, and an outlet configured to be coupled to one end of the needle, a first pressure sensor coupled to the tubing system, a second pressure sensor coupled to the tubing system, and a piezoelectric pump coupled to the inlet and the outlet, wherein: the piezoelectric pump is configured to cause a fluid from the reservoir to be drawn into the inlet to allow the fluid to flow through the tubing system and into the needle, the first pressure sensor is configured to provide a first measurement associated with a pressure difference between the fluid in the tubing system and an environment, the second pressure sensor is configured to provide a second measurement associated with a pressure difference of the fluid across a known length of the tubing system, and the display is configured to provide a flow rate reading or a pressure reading based on the first measurement or the second measurement; placing a tip of the needle at a location where an injection into a tissue is to be performed;27009062.8556. WOOO\183747782.1PCT Patent Application 009062.8556.WOOO causing the tip of the needle to advance into one or more layers of the tissue; and providing the flow rate reading or the pressure reading on the display at one or more times as the tip advances into the one or more layers to enable a determination as to whether the tip has reached the targeted location, wherein the determination is based on the flow rate reading or the pressure reading at the one or more times.

17. The method of claim 16, comprising: operating the injection system to cause the fluid to be dispensed through the tip and into the targeted location.

18. The method of claim 16, wherein the injection system further comprises: a printed circuit board (PCB) comprising a signal conditioning circuit; a fitting coupled to the outlet and the one end of the needle, wherein: the fluid is allowed to flow through the outlet and out of the tip based on a configuration of the fitting, the first pressure sensor and the second pressure sensor are disposed on the PCB, the signal conditioning circuit is configured to provide a signal by removing high- frequency noise from the first measurement or the second measurement, and the signal conditioning circuit comprises an amplifier configured to amplify the signal to a measurable voltage.

19. The method of claim 18, wherein the measurable voltage is used to obtain the flow rate reading or the pressure reading.

20. The method of claim 16, wherein the targeted location is an epidural space in a back of a human body.28009062.8556. WOOO\183747782.1

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