System for compensating arterial pressure sensor positioning

Abstract

A system for compensating for arterial pressure sensor positioning includes: a pressure transducer; an arterial line coupled to the pressure transducer; and a fluid column coupled to the pressure transducer. Various system configurations may be used to calibrate the pressure transducer to automatically account for pressure due to the vertical distance between the venous statics axis and the pressure transducer. Various system configurations may be used to detect the vertical distance between the venous statics axis and the pressure transducer and adjust the pressure readings accordingly. Various system configurations may be used to position the pressure transducer at the venous statics axis.

Description

Technical Field

[0001] The present disclosure generally relates to systems for compensating for arterial pressure sensor positioning. Background Art

[0002] Arterial lines are placed to obtain real-time blood pressure and allow for arterial blood gas sampling. Figure 1 An example of a prior art system 100 that can be used to measure arterial pressure is provided. System 100 includes a recording device 101, a pressure transducer 103 connected to the recording device 101 via a cable 102, and a pressure conduit 104 connected between the pressure transducer 103 and the arterial line. One or more three-way stopcocks 105 may be positioned on or in communication with the pressure conduit 104.

[0003] System 100 also includes a pressure infuser 111 that is connected to the pressure transducer 103 via a conduit 112. The conduit 112 may be coupled to the pressure infuser 111 via a drip chamber 113. A clamp 114 may be positioned on the conduit 112 to control the flow of fluid therethrough.

[0004] The pressure transducer 103 is positioned at the phlebostatic axis 123 (which generally corresponds to the position of the right atrium and the aortic root and is identified as the intersection between a line 121 representing the midpoint, anterior and posterior chest walls and a line 122 representing the fourth intercostal space at the sternum) and is connected to the pressure infuser 111. The pressure infuser 111 is pressurized to 300 mmHg, and the flow is throttled to a rate of about 3 ml / hr by a flow restrictor in the pressure transducer 103. The purpose of the 3 ml / hr flow rate is to keep the pressure conduit 104 free of air bubbles and to prevent blood from flowing back into the catheter and causing an occlusion. The pressure transducer 103 is zeroed to the atmosphere to allow for the measurement of the gauge pressure of the aorta.

[0005] These prior arts have various problems. For example, a good pressure waveform may be lost due to air bubbles, catheter kinking, occlusion, etc. In addition, when the patient is repositioned or the bed is tilted or declined, the transducer height may need to be continuously adjusted. Setting up the conduits, sensors, pressure infusion, etc. is also time-consuming.

[0006] The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is provided only to illustrate an example technical field in which some of the embodiments described herein may be practiced. Summary of the Utility Model

[0007] The present disclosure generally relates to systems and methods for compensating for arterial pressure sensor positioning. Various system configurations can be used to calibrate a pressure transducer to automatically account for the pressure attributable to the vertical distance between the venous hydrostatic axis and the pressure transducer. Various system configurations can be used to detect the vertical distance between the venous hydrostatic axis and the pressure transducer and adjust the pressure reading accordingly. Various system configurations can be used to position the pressure transducer at the venous hydrostatic axis.

[0008] In some embodiments of the present disclosure, a system for compensating for arterial pressure sensor positioning includes: a pressure transducer; an arterial line coupled to the pressure transducer; and a fluid column coupled to the pressure transducer.

[0009] In some embodiments, the top of the fluid column can be positioned at the patient's venous hydrostatic axis.

[0010] In some embodiments, the pressure transducer can be positioned at a height below the venous hydrostatic axis.

[0011] In some embodiments, the pressure transducer can generate a pressure reading indicative of arterial pressure that accounts for the height at which the pressure transducer is positioned below the venous hydrostatic axis.

[0012] In some embodiments, the system can further include a pressure monitoring device that receives the pressure reading from the pressure transducer.

[0013] In some embodiments of the present disclosure, a system for compensating for arterial pressure sensor positioning includes: a pressure transducer configured to generate a pressure reading indicative of arterial pressure; and a pressure monitoring device configured to receive the pressure reading from the pressure transducer.

[0014] In some embodiments, the system can further include a first transmitter located at the pressure transducer, a second transmitter located at the patient's venous hydrostatic axis, and a plurality of sensors that receive signals from the first transmitter and the second transmitter for calculating the height at which the pressure transducer is positioned below the venous hydrostatic axis. The pressure monitoring device is configured to use the calculated height to determine arterial pressure from the pressure reading.

[0015] In some embodiments, the system can further include a control box located at the patient's venous hydrostatic axis and shape-sensing fibers connected between the control box and the pressure transducer, the control box being configured to use the shape-sensing fibers to calculate the height at which the pressure transducer is positioned below the venous hydrostatic axis. The pressure monitoring device is configured to use the calculated height to determine arterial pressure from the pressure reading.

[0016] In some embodiments, the system may further include a first reference located at the pressure transducer, a second reference located at the patient's venous hydrostatic axis, and a camera configured to use the first reference and the second reference to calculate the height at which the pressure transducer is located below the venous hydrostatic axis. The pressure monitoring device is configured to use the calculated height to determine the arterial pressure from the pressure readings.

[0017] In some embodiments, the system may further include a first barometric pressure sensor located at the pressure transducer and a second barometric pressure sensor located at the patient's venous hydrostatic axis. The pressure monitoring device is configured to use the first barometric pressure sensor and the second barometric pressure sensor to calculate the height at which the pressure transducer is located below the venous hydrostatic axis, and to use the calculated height to determine the arterial pressure from the pressure readings.

[0018] In some embodiments, the pressure monitoring device is configured to receive a first pressure reading when the pressure transducer is located at the patient's venous hydrostatic axis, receive a second pressure reading when the pressure transducer is at a height below the venous hydrostatic axis, and use the first pressure reading and the second pressure reading to determine the arterial pressure from subsequent pressure readings.

[0019] In some embodiments, the arterial pressure may be determined by subtracting the first pressure reading and the second pressure reading from subsequent pressure readings.

[0020] In some embodiments, the pressure transducer includes an accelerometer and a gyroscope, and wherein the pressure monitoring device is configured to use the accelerometer and the gyroscope to calculate the height at which the pressure transducer is located below the patient's venous hydrostatic axis, and to use the calculated height to determine the arterial pressure from the pressure readings.

[0021] In some embodiments, the pressure transducer is a first pressure transducer, the system may further include a second pressure transducer and a fluid column connected to the second pressure transducer, the top of the second fluid column being located at the patient's venous hydrostatic axis. The pressure monitoring device receives the pressure readings of the first pressure transducer and the second pressure transducer, and the pressure monitoring device is configured to determine the arterial pressure from the pressure reading of the first pressure transducer by using the pressure reading of the second pressure transducer to account for the height at which the first pressure transducer is located below the venous hydrostatic axis.

[0022] In some embodiments, the pressure transducer may be located within the patient's artery.

[0023] In some embodiments, the system may further include a sensor positioned at the hydrostatic axis of the patient's vein. The sensor may be configured to detect the height at which the pressure transducer is below the hydrostatic axis of the vein.

[0024] In some embodiments, the system may further include a magnetic sensor positioned at one of the pressure transducer or the hydrostatic axis of the patient's vein and one or more Hall sensors positioned at the other of the pressure transducer or the hydrostatic axis. The pressure monitoring device is configured to use the magnetic sensor and the one or more Hall sensors to calculate the height at which the pressure transducer is below the hydrostatic axis and to use the calculated height to determine the arterial pressure from the pressure reading.

[0025] In some embodiments of the present disclosure, a method for determining arterial pressure may include obtaining a pressure reading using a pressure transducer, determining the height of the pressure transducer below the hydrostatic axis, and determining the arterial pressure from the pressure reading and the height.

[0026] In some embodiments, the pressure transducer may be connected to an arterial line and a fluid column, the top of the fluid column being positioned at the hydrostatic axis.

[0027] In some embodiments, determining the arterial pressure from the pressure reading and the height may include configuring the pressure transducer to account for the height in the pressure reading.

[0028] In some embodiments, determining the arterial pressure from the pressure reading and the height may include calculating the component of the pressure reading attributable to the height.

[0029] In some embodiments of the present disclosure, a system for compensating for the positioning of an arterial pressure sensor may include a pressure transducer configured to generate a pressure reading, an arterial line coupled to the pressure transducer, a fluid column coupled to the pressure transducer, and a pressure monitoring device configured to output an arterial pressure from the pressure reading, the arterial pressure taking into account the height at which the pressure transducer is below the hydrostatic axis.

[0030] It should be understood that the foregoing general description and the following detailed description are both exemplary and explanatory and are not limiting of the claimed utility model. It should be understood that the various embodiments are not limited to the arrangements and instruments shown in the drawings. It should also be understood that embodiments may be combined, or other embodiments may be utilized, and structural changes may be made without departing from the scope of the various embodiments of the present utility model, unless so claimed. Accordingly, the following detailed description is not limiting. Description of the Drawings

[0031] Exemplary embodiments will be described and explained with additional specificity and detail by using the drawings, in which:

[0032] Figure 1 illustrates an existing technology system that can be used to monitor arterial pressure;

[0033] Figure 2A and Figure 2B provides an example of a system constructed according to one or more embodiments of the present disclosure for compensating for arterial pressure sensor positioning;

[0034] Figure 3 provides an example of a system constructed according to one or more embodiments of the present disclosure for compensating for arterial pressure sensor positioning;

[0035] Figure 4 provides an example of a system constructed according to one or more embodiments of the present disclosure for compensating for arterial pressure sensor positioning;

[0036] Figure 5 provides an example of a system constructed according to one or more embodiments of the present disclosure for compensating for arterial pressure sensor positioning;

[0037] Figure 6 provides an example of a system constructed according to one or more embodiments of the present disclosure for compensating for arterial pressure sensor positioning;

[0038] Figure 7A and Figure 7B provides examples of systems and methods for compensating for arterial pressure sensor positioning according to one or more embodiments of the present disclosure; and

[0039] Figure 8 provides an example of a system constructed according to one or more embodiments of the present disclosure for compensating for arterial pressure sensor positioning. DETAILED DESCRIPTION

[0040] Figure 2A provides an example of a system 200 for compensating for arterial pressure sensor positioning constructed according to one or more embodiments of the present disclosure. The system 200 includes a pressure transducer 210 that is positioned proximal to the arterial line 240. As Figure 2B shown, the pressure transducer 210 may include a diaphragm 211 and a circuit 212 for measuring the pressure difference across the diaphragm 211. The arterial line 240 may be connected to the distal end of the pressure transducer 210, and the fluid column 220 may be connected to the proximal end of the pressure transducer 210. Thus, the blood pressure in the arterial line 240 will impinge on the distal face of the diaphragm 211, and the fluid pressure in the fluid column 220 will impinge on the proximal face of the diaphragm 211.

[0041] The armband 230 can be used to fix and stabilize the fluid column 220 on the patient's arm. The top 220a of the fluid column 220 (e.g., the highest point of the fluid in the fluid column 220) can be positioned at the venous statics axis 123. When the top 220a of the fluid column 220 is at the venous statics axis 123 and the pressure transducer 210 is in its intended / desired position and the diaphragm 211 is not exposed to arterial pressure, the pressure transducer 210 can be zeroed. This can be achieved using a stopcock on the arterial line 240 or before connecting the arterial line 240 to the pressure transducer 210. Then, the diaphragm 211 can be exposed to arterial pressure (e.g., by opening the stopcock, attaching the arterial line 240, etc.). The pressure measurement subsequently provided by the pressure transducer 210 will accurately represent the arterial pressure as long as the top 220a of the fluid column 220 remains at or near the venous statics axis 123, which will typically be the case when the patient is lying in a hospital bed. The pressure transducer 210 can be configured to transmit these pressure measurements to the pressure monitoring device 250 via a wired connection, a wireless connection, or both.

[0042] More particularly, the height (h) between the venous statics axis 123 and the position of the pressure transducer 210 is a parameter of the pressure exerted by the fluid column 220 and the blood in the arterial line 240 on the diaphragm 211. In all cases, this pressure is equal to pgh, where p is the blood density, g is the acceleration due to gravity, and h is the vertical distance between the venous statics axis 123 and the pressure transducer 210. By positioning the top 220a of the fluid column 220 at the venous statics axis 123 and zeroing the pressure transducer 210 before connecting the arterial line 240, the blood pressure attributable to the height (h) can be offset by the pressure of the fluid column 220, such that the pressure measurement only reflects the arterial pressure. The following equation can represent this pressure: P transducer = P artery + pgh artery – pgh fluid_column . In the system 200, pgh fluid_column will be equal to and thus cancel out pgh artery .

[0043] The system 200 can provide various benefits. For example, since the pressure transducer 210 can be positioned at the insertion point, the distance between the artery and the pressure transducer 210 is minimized, which can result in a more accurate pressure waveform. This shorter distance can also minimize the risk of air bubbles. The system 200 is also easier to connect and disconnect because there may only be a single cable or even a wireless connection between the pressure transducer 210 and the pressure monitoring device 250.

[0044] In some embodiments, a system for compensating for arterial pressure sensor positioning can be configured to detect / calculate the height (h) between the venous hydrostatic axis 123 and the pressure transducer 210 and automatically adjust the pressure measurement based on that height. For example, given the height (h), the pressure transducer 210 and / or the pressure monitoring device 250 can calculate the pressure (pgh fluid_column ) exerted by the fluid column 220 on the diaphragm 211 and the pressure (pgh artery ) attributable to the height (h) of the arterial blood exerted on the diaphragm 211, and then use these pressures to calculate the arterial pressure (P artery ). Figures 3 - 6 Some examples of systems that work in this way are provided.

[0045] Figure 3 Examples of a system 300 for compensating for arterial pressure sensor positioning constructed in accordance with one or more embodiments of the present disclosure are provided. The system 300 can include a pressure transducer 210 connected to an arterial line 240. Alternatively, the pressure transducer 210 can be positioned in the artery, in a catheter, or otherwise positioned to sense arterial pressure. Additionally, the system 300 can include a first transmitter 301a, a second transmitter 301b, and a plurality of sensors 302. The first transmitter 301a can be positioned at the pressure transducer 210 (or more particularly, at the point where the arterial line 240 is connected to the pressure transducer 210, or at the point where the pressure transducer 210 is subjected to arterial pressure), and the second transmitter 301 can be positioned at the venous hydrostatic axis 123 (e.g., on the patient's arm, on the bed, etc.). The sensors 302 can be positioned around the patient, such as on the walls or ceiling of the room. The first transmitter 301a and the second transmitter 301b can be configured to transmit signals, and the sensors 302 can use the signals to triangulate the positions of the transmitters to calculate the height (h). Thus, in some embodiments, at least three sensors 302 can be used.

[0046] Figure 4An example of a system 400 for compensating for arterial pressure sensor positioning constructed in accordance with one or more embodiments of the present disclosure is provided. The system 400 may include a pressure transducer 210 connected to an arterial line 240. Alternatively, the pressure transducer 210 may be positioned in the artery, in a catheter, or otherwise positioned to sense arterial pressure. Additionally, the system 400 may include a control box 410 positioned at the venous hydrostatic axis 123, which is connected to the pressure transducer 210 via a shape-sensing fiber 411. For example, the control box 410 may be positioned on a pole, a bed, or other structure near the patient. The control box 410 may be configured to detect the height (h) using the shape-sensing fiber 411. In particular, the control box 410 may detect the shape of the shape-sensing fiber 411 and may use the detected shape to calculate the vertical distance (h) between the control box 410 and the end of the shape-sensing fiber 411 located at the pressure transducer 210.

[0047] In some embodiments, a sensor may be positioned at the venous hydrostatic axis and configured to detect the height (h). For example, the sensor may be configured to detect the height (h) by calculating the relative height between its known position at the venous hydrostatic axis and the detected position of the pressure transducer. The sensor may detect the relative height using vision (e.g., as a camera), via light or another signal emitted from the pressure transducer 210, or in some other manner. In some embodiments, the sensor may be configured to automatically move up and down to remain level with the venous hydrostatic axis.

[0048] Figure 5 An example of a system 500 for compensating for arterial pressure sensor positioning constructed in accordance with one or more embodiments of the present disclosure is provided. The system 500 may include a pressure transducer 210 connected to an arterial line 240. Alternatively, the pressure transducer 210 may be positioned in the artery, in a catheter, or otherwise positioned to sense arterial pressure. Additionally, the system 500 may include a first visual fiducial 501a positioned at the pressure transducer 210 and a second visual fiducial 501b positioned at the venous hydrostatic axis 123. The system 500 may further include a camera 251, which may be part of a pressure monitoring device 250, part of another computing device, or an independent camera. The camera 251 may be configured to capture images including both the first visual fiducial 501a and the second visual fiducial 501b and to calculate the height (h) from these images.

[0049] In a variant of the system 500, in contrast to the visual reference, the infrared reference can be positioned at the pressure transducer 210 and the venous hydrostatic axis 123, and multiple infrared cameras can be used to determine the height (h) between the infrared references. For example, the infrared cameras can be oriented in two orthogonal directions, and based on the relative positions between the orthogonal directions and the detected infrared references, the height (h) can be calculated.

[0050] In some embodiments of the system 500, the camera 251 can be part of a smartphone. In such embodiments, a mobile application can be configured to use the images captured by the camera 251 to determine the height (h) based on the references present in the images. In some embodiments, the system 500 may not include references. Instead, the mobile application can allow the user to specify the positions of the pressure transducer 210 and the venous hydrostatic axis 123 in the captured images, and then the height (h) can be determined based on such input.

[0051] Figure 6 An example of a system 600 constructed in accordance with one or more embodiments of the present disclosure for compensating for arterial pressure sensor positioning is provided. The system 600 can include a pressure transducer 210 connected to the arterial line 240. Alternatively, the pressure transducer 210 can be positioned in the artery, in a catheter, or otherwise positioned to be able to sense arterial pressure. Additionally, the system 600 can include a first barometer sensor 601a positioned at the pressure transducer 210 and a second barometer sensor 601b positioned at the venous hydrostatic axis 123. The first barometer sensor 601a and the second barometer sensor 601b can provide barometric measurements (e.g., provided to the pressure monitoring device 250 or another computing device), and the barometric measurements can be used to calculate the height (h) based on the difference between these barometric measurements.

[0052] In a variant of the system 600, other types of sensors can be used. For example, magnetic sensors can be positioned at the pressure transducer 210 or the venous hydrostatic axis 123, and one or more Hall effect sensors can be positioned at another location. The one or more Hall effect sensors can determine the direction and distance of the magnetic sensors. One of these sensors can also include a gyroscope capable of determining the horizontal axis. Using the known horizontal axis and the direction of the magnetic sensors detected by the one or more Hall effect sensors, the height (h) can be calculated.

[0053] Figure 7A and Figure 7BExamples of a system 700 and method for compensating for arterial pressure sensor positioning constructed in accordance with one or more embodiments of the present disclosure are provided. The system 700 may include a pressure transducer 210 connected to an arterial line 240. Alternatively, the pressure transducer 210 may be positioned in an artery, in a catheter, or otherwise positioned to sense arterial pressure. Additionally, a pressure monitoring device 250 may be configured to receive a pressure reading (Pressure1) when the pressure transducer 210 is positioned at the venous hydrostatic axis 123, and to receive a pressure reading (Pressure2) when the pressure transducer 210 is positioned at the intended / desired location. The pressure attributable to height (h) may then be calculated as Pressure2 - Pressure1. The pressure monitoring device 250 may then calculate the arterial pressure (i.e., Pressure artery = Pressure transducer - Pressure2 - Pressure1) from subsequent pressure readings when the pressure transducer is positioned at the intended / desired location by subtracting the pressure attributable to height (h). A similar result may be achieved by zeroing the pressure transducer 210 (i.e., making Pressure1 equal to 0) when the pressure transducer is positioned at the venous hydrostatic axis 123.

[0054] When the pressure transducer 210 includes an accelerometer and a gyroscope, a similar method may be used to calculate arterial pressure. In this case, the position calculated from the readings of the accelerometer and gyroscope may be zeroed with the pressure transducer 210 positioned at the venous hydrostatic axis 123. Subsequently, the subsequent readings of the accelerometer and gyroscope may be used to calculate the height (h).

[0055] Similar methods may be used to calculate arterial pressure using a blood pressure cuff. The blood pressure cuff may be placed on the upper arm to measure blood pressure. The measured blood pressure may then be used to zero and calibrate the pressure transducer 210. This process may be repeated periodically (e.g., every hour, once a day, whenever the mean arterial pressure changes significantly, etc.) to automatically re-zero and calibrate the pressure transducer 210.

[0056] Figure 8An example of a system 800 for compensating for arterial pressure sensor positioning constructed in accordance with one or more embodiments of the present disclosure is provided. The system 800 may be constructed in a similar manner to the system 200, except that the pressure transducer 210 is not connected to the arterial line 240. Instead, the system 800 may include a second pressure transducer 810 that is connected to the arterial line 240 and is positioned within the artery, within the catheter, or otherwise positioned to sense arterial pressure. In these embodiments, the pressure reported by the pressure transducer 210 will be based on the height (h), and may be used to adjust the pressure reported by the second pressure transducer 810 to account for the height (h) of the second pressure transducer 810 below the venous hydrostatic axis.

[0057] As described above, the pressure transducer 210 and / or 810 may be positioned within the artery, rather than outside the body as shown, or within the catheter. In some embodiments, the pressure transducer 210 and / or 810 may be a dual gauge pressure transducer. In some embodiments, the fluid column 220 may be fixed to a location other than the patient's arm, such as to the bed, the monitor pole, the IV pole, etc.

[0058] In some embodiments, the pressure transducer may be positioned at the venous hydrostatic axis 123. For example, the pressure transducer may be threaded along the artery to a location at the venous hydrostatic axis. From the radial artery, the pressure transducer may be threaded to the brachial artery that is horizontal with the venous hydrostatic axis. From the femoral artery, the pressure transducer may be advanced upward to the aorta. Thus, there is no height difference between the venous hydrostatic axis and the pressure transducer. In such embodiments, the position of the pressure transducer may be determined by a variety of techniques including Sherlock, ultrasound, etc.

[0059] In any of the above embodiments, when the mean arterial pressure changes, various techniques may be used to automatically alert the clinician. For example, when the pressure transducer 210 includes an accelerometer, the accelerometer may be used to detect when movement occurs. If movement is detected but no change in mean arterial pressure is detected, the movement may be ignored. However, if no movement is detected when a change in mean arterial pressure is detected, the clinician may be alerted to check the patient. Additionally, if both movement and a change in mean arterial pressure are detected, the clinician may be alerted to re-zero the pressure transducer 210 if necessary.

[0060] As another example, the system may be configured to detect when the bed moves (e.g., reclines or tilts). When the bed is moved, the clinician may be alerted to check if the venous hydrostatic axis may have changed. If so, the clinician may re-zero the pressure transducer 210.

[0061] All the examples and conditional language described herein are for teaching purposes to assist the reader in understanding the present utility model and the concepts contributed by the inventor to further advance the field, and should be construed as not limited to these specifically described examples and conditions. Although the embodiments of the present utility model have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the present utility model.

Claims

1. A system for compensating for the positioning of an arterial pressure sensor, characterized in that, The system includes: A pressure transducer; An arterial line connected to the pressure transducer; and A fluid column connected to the pressure transducer.

2. The system according to claim 1, wherein The top of the fluid column is positioned at the venous hydrostatic axis of the patient.

3. The system according to claim 2, wherein The pressure transducer is positioned at a height below the venous hydrostatic axis.

4. The system according to claim 3, wherein The pressure transducer generates a pressure reading indicative of arterial pressure, and the pressure reading takes into account the height at which the pressure transducer is positioned below the venous hydrostatic axis.

5. The system according to claim 4, wherein The system further includes: A pressure monitoring device that receives the pressure reading from the pressure transducer.

6. A system for compensating for the positioning of an arterial pressure sensor, characterized in that, The system includes: A pressure transducer configured to generate a pressure reading indicative of arterial pressure; and A pressure monitoring device configured to receive the pressure reading from the pressure transducer.

7. The system according to claim 6, wherein The system further includes: A first transmitter positioned at the pressure transducer; A second transmitter positioned at the venous hydrostatic axis of the patient; and A plurality of sensors that receive signals from the first transmitter and the second transmitter, wherein the signals are used to calculate the height at which the pressure transducer is positioned below the venous hydrostatic axis; wherein the pressure monitoring device is configured to use the calculated height to determine arterial pressure from the pressure reading.

8. The system according to claim 6, wherein The system further includes: A control box positioned at the venous hydrostatic axis of the patient; and Shape-sensing fibers connected between the control box and the pressure transducer, wherein the control box is configured to use the shape-sensing fibers to calculate the height at which the pressure transducer is located below the venous hydrostatic axis; wherein the pressure monitoring device is configured to use the calculated height to determine arterial pressure from the pressure reading.

9. The system according to claim 6, wherein The system further includes: A first reference positioned at the pressure transducer; A second reference positioned at the venous hydrostatic axis of the patient; and A camera configured to use the first reference and the second reference to calculate the height at which the pressure transducer is positioned below the venous hydrostatic axis; wherein the pressure monitoring device is configured to use the calculated height to determine arterial pressure from the pressure reading.

10. The system according to claim 6, characterized in that, The system further includes: A first barometer sensor positioned at the pressure transducer; and A second barometer sensor positioned at the venous hydrostatic axis of the patient; wherein the pressure monitoring device is configured to use the first barometer sensor and the second barometer sensor to calculate the height at which the pressure transducer is located below the venous hydrostatic axis, and use the calculated height to determine arterial pressure from the pressure reading.

11. The system according to claim 6, wherein The pressure monitoring device is configured to receive a first pressure reading when the pressure transducer is positioned at the patient's venous hydrostatic axis, receive a second pressure reading when the pressure transducer is positioned at a height below the venous hydrostatic axis, and determine arterial pressure from subsequent pressure readings using the first pressure reading and the second pressure reading.

12. The system according to claim 11, wherein The arterial pressure is determined by subtracting both the first pressure reading and the second pressure reading from the subsequent pressure readings.

13. The system according to claim 6, wherein The pressure transducer includes an accelerometer and a gyroscope, and wherein the pressure monitoring device is configured to use the accelerometer and the gyroscope to calculate the height at which the pressure transducer is below the patient's venous hydrostatic axis, and use the calculated height to determine arterial pressure from the pressure readings.

14. The system according to claim 6, characterized in that, The pressure transducer is a first pressure transducer, and the system further includes: A second pressure transducer; and A fluid column connected to the second pressure transducer, the top of the fluid column being positioned at the patient's venous hydrostatic axis; Wherein the pressure monitoring device receives pressure readings from the first pressure transducer and the second pressure transducer, and the pressure monitoring device is configured to determine arterial pressure from the pressure readings of the first pressure transducer by using the pressure readings of the second pressure transducer to account for the height at which the first pressure transducer is below the venous hydrostatic axis.

15. The system according to claim 6, wherein The pressure transducer is positioned within the patient's artery.

16. The system according to claim 6, wherein The system further includes: A sensor positioned at the patient's venous hydrostatic axis, the sensor being configured to detect the height at which the pressure transducer is below the venous hydrostatic axis.

17. The system according to claim 6, wherein The system further includes: A magnetic sensor positioned at one of the pressure transducer and the patient's venous hydrostatic axis; and One or more Hall sensors positioned at the other of the pressure transducer and the venous hydrostatic axis; Wherein the pressure monitoring device is configured to use the magnetic sensor and the one or more Hall sensors to calculate the height at which the pressure transducer is below the venous hydrostatic axis, and use the calculated height to determine arterial pressure from the pressure readings.

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