Patent Publication Number: US-2018028794-A1

Title: Drainage systems for excess body fluids and associated methods

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/973,548, which is a divisional of U.S. patent application Ser. No. 13/488,326, which claims the benefit of U.S. Provisional Patent Application No. 61/493,091, filed Jun. 3, 2011, U.S. Provisional Patent Application No. 61/591,668, filed Jan. 27, 2012, and U.S. Provisional Patent Application No. 61/654,600, filed Jun. 1, 2012, and is a continuation-in-part of PCT Patent Application No. PCT/US2011/029261, filed Mar. 21, 2011, which claims the benefit of U.S. Provisional Patent Application No. 61/315,660, filed Mar. 19, 2010; and U.S. Provisional Patent Application No. 61/407,359, filed Oct. 27, 2010. All of the foregoing applications are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present technology relates generally to draining excess body fluids. In particular, several embodiments are directed toward body fluid drainage systems with enhanced drainage regulation and associated methods. 
     BACKGROUND 
     A variety of medical conditions cause the collection of excess body fluids within the human body. Hydrocephalus, for example, is an accumulation of excess cerebrospinal fluid (“CSF”) in the ventricles of the brain that increases intracranial pressure (“ICP”). This condition can be caused by the inability to reabsorb CSF, impaired CSF flow, or excessive production of CSF. Acute accumulations of excess CSF can also occur from brain trauma, brain hemorrhaging, strokes, brain tumors, spinal fluid leaks, meningitis, and brain abscesses. When left untreated, hydrocephalus and other excess accumulations of CSF can progressively enlarge the ventricles of the brain, which can increase ICP and cause convulsions, mental disabilities, and eventually death. 
     Treatment for hydrocephalus generally requires the installation of a CSF shunt that drains CSF from the brain to an alternate location that can collect the excess CSF or reabsorb it into the body. A ventriculoperitoneal shunt (“VPS”), for example, includes a subcutaneously installed catheter inserted in the lateral ventricle (i.e., a site of excess CSF) and in fluid communication with the peritoneal cavity to facilitate reabsorbtion of the excess CSF into the body. A mechanical valve, generally implanted flush with the skull, can regulate CSF flow through the catheter. Recent innovations have resulted in VPSs that can regulate CSF movement based on static pressure parameters. For example, an external magnetic field can be applied to the implanted VPS to change the set point pressure of the valve. 
     Similar to hydrocephalus, acute accumulations of CSF are treated by shunting excess CSF to an alternate location. For example, temporary CSF diversion generally includes the installation of an external ventricular drain (“EVD”) that funnels CSF from the lateral ventricle to an external drainage chamber, and thereby reduces the intracranial CSF volume and lowers ICP. Alternatively, temporary CSF diversion can include placing a lumbar drain (“LD”) at the base of the spine, and draining CSF from the lumbar region to an external drainage chamber. Despite having different insertion points, EVDs and LDs use the similar components to control drainage. 
     In general, temporary and more permanent CSF diversion devices (e.g., VPSs) include similar features, and thus incur many of the same complications. Infection, for example, can be a significant risk factor both during and after implantation of a CSF shunt. When an infection occurs, the entire CSF shunt must be removed, and the patient must generally undergo 10-14 days of IV antibiotics and re-internalization of a new CSF shunt. Mechanical failure can occur within each component of a CSF shunt, and generally requires the replacement of the failed component(s). The inlet of the catheter, for example, can incur in-growth of intraventricular tissue. Valves can fail due to debris build-up (e.g., blood, protein) within the valve, and the outlet of the catheter can fail by fracturing, becoming obstructed, or tethering within scar tissue. These mechanical failures, infections, and other complications cause a majority of implanted CSF shunts to fail within two years and nearly all shunts fail within ten years. Due to this unreliability and the necessity to locally monitor and adjust ICPs, conventional CSF shunts require frequent intervention by medical professionals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic view of an internal body fluid drainage system installed within a patient in accordance with an embodiment of the present technology. 
         FIG. 1B  is a schematic view of an external body fluid drainage system installed in a patient in accordance with an embodiment of the present technology. 
         FIG. 2A  is an enlarged schematic, cross-sectional view of a valve device in accordance with an embodiment of the present technology. 
         FIG. 2B  is an enlarged schematic, cross-sectional view of a valve device in accordance with another embodiment of the present technology. 
         FIGS. 3A-3J  are side views of actuators for a valve device in accordance with embodiments of the present technology. 
         FIGS. 4A and 4B  are side and perspective views, respectively, of reservoirs for a body fluid drainage system in accordance with embodiments of the present technology. 
         FIG. 5A  is a schematic, cross-sectional top plan view of unobstructed antegrade flow through a valve device of a body fluid drainage system in accordance with an embodiment of the present technology. 
         FIG. 5B  is a schematic, cross-sectional top plan view of partially obstructed antegrade flow through the valve device of  FIG. 5A . 
         FIG. 5C  is a schematic, cross-sectional top plan view of retrograde flow through the valve device of  FIG. 5A . 
         FIG. 5D  is a schematic, cross-sectional top plan view of forced antegrade flow through the valve device of  FIG. 5A . 
         FIG. 6A  is a schematic, cross-sectional side view of antegrade flow through a body fluid drainage system implanted in a ventricle in accordance with an embodiment of the present technology. 
         FIG. 6B  is a schematic, cross-sectional top view of retrograde flow through the body fluid drainage system of  FIG. 6A . 
         FIG. 7A  is a partial schematic view of a body fluid drainage system in accordance with a further embodiment of the present technology. 
         FIGS. 7B-7D  are schematic views of portions of the body fluid drainage system of  FIG. 7A . 
         FIGS. 8A and 8B  are schematic views of external body fluid drainage systems installed in different portions of a CSF system in accordance with additional embodiments of the present technology. 
     
    
    
     DETAILED DESCRIPTION 
     The present technology is directed to devices, systems, and methods for draining excess body fluids. In one embodiment, for example, a body fluid drainage system can be installed between a site of excess body fluid in a patient and a second location (e.g., an external receptacle, an internal cavity) that can collect and/or reabsorb the excess body fluid. The body fluid drainage system can include a valve device that applies incremental forces to an exterior of a catheter to regulate the drainage rate of the body fluid. In selected embodiments, the body fluid drainage system can also generate forced flow of the body fluid through the catheter to both prevent obstructions and perform diagnostics on the system. Certain specific details are set forth in the following description and in  FIGS. 1A-8B  to provide a thorough understanding of various embodiments of the technology. For example, several embodiments of body fluid drainage systems that shunt cerebrospinal fluid (“CSF”) are described in detail below. The present technology, however, may be used to drain a variety of excess body fluids, such as peritoneal fluid, blood, water, and/or other body fluids. Additionally, the term “catheter” is used broadly throughout the application to refer to any suitable tubing or structure that includes a lumen through which body fluids can flow. Other details describing well-known structures and systems often associated with CSF and other body fluid drainage systems, shunts, biomedical diagnostics, etc. have not been set forth in the following disclosure to avoid unnecessarily obscuring the description of the various embodiments of the technology. A person of ordinary skill in the art, therefore, will accordingly understand that the technology may have other embodiments with additional elements, or the technology may have other embodiments without several of the features shown and described below with reference to  FIGS. 1A-8B . 
     As used herein, the term “force” refers to the interaction between an actuator and a catheter. This term is used broadly, and in some embodiments “pressure” is an equally valid term. Additionally, in selected embodiments, the actuator can apply a force or a pressure to the catheter by changing the position of the actuator mechanism (e.g., a linear shaft, a rotary shaft, a screw shaft) relative to the catheter, thus “actuator position” may also be used to describe the interaction between the actuator and the catheter. 
       FIG. 1A  is a schematic view of an internal body fluid drainage system  100  (“drainage system  100 ”) implanted in a patient  101  in accordance with an embodiment of the present technology. The drainage system  100  can include a catheter  102 , a valve device  104  over an exterior surface  112  of the catheter  102 , and one or more sensors  106  (identified individually as a first sensor  106   a  and a second sensor  106   b ). The drainage system  100  can also include a controller  110  that is operatively coupled to the valve device  104  and/or the sensors  106 . As described in further detail below, the valve device  104  can apply incremental forces to the exterior surface  112  of the catheter  102  to regulate body fluid flow through the catheter  102 , and the controller  110  can alter the level of force applied by the valve device  104  on the catheter  102  in response to measurements (e.g., pressure, flow rate) taken from the sensors  106 . 
     As shown in  FIG. 1A , the catheter  102  can include a proximal portion  108   a  and a distal portion  108   b  opposite the proximal portion  108   a.  The proximal and distal portions  108   a - b  of the catheter  102  can be an integrally formed tube or include two or more separate tubes joined together using suitable fastening methods (e.g., gluing) known in the art. The catheter  102  can be made from a range of polymers, such as silicone, latex, thermoplastic elastomers, and/or other suitable tubing materials. In selected embodiments, portions of the catheter proximate to the valve device  104  can include compressible peristaltic pump tubing (e.g., silicone rubber, polyvinyl chloride), reduced fouling surfaces, tubing with different mechanical compliances, and/or other durable elastomeric materials that resist fatigue. In other embodiments, the catheter  102  can be made from tubing with biocides and/or other anti-biofouling agents that prevent organisms from entering the drainage system  100  and causing infection. When the catheter  102  includes different materials and/or sections of tubing, the different materials and/or portions can be sealed together with adhesives and/or other fasteners that provide a liquid-tight seal. 
     The proximal portion  108   a  of the catheter  102  is positioned at a site of excess body fluid and the distal portion  108   b  can be placed in fluid communication with an internal receptacle that collects and/or absorbs the body fluid. The proximal portion  108   a  of the catheter  102  can include an inlet region  116  with one or more openings (not visible) in fluid communication with a site of excess body fluid such that the body fluid can flow into the catheter  102 . In the embodiment illustrated in  FIG. 1A , for example, the inlet region  116  of the catheter  102  is installed (e.g., via a burr hole) into a ventricle  113  of the patient&#39;s brain to receive excess CSF. After entering the drainage system  100 , the body fluid can travel in an antegrade flow through the catheter  102  to the distal portion  108   b.  The distal portion  108   b  can include an outlet region  118  that expels the excess body fluid into an internal location. For example, the outlet region  118  can be placed in fluid communication with the patient&#39;s peritoneal cavity  115 , where excess body fluid can reabsorb into the body. In other embodiments, the outlet region  118  can expel the body fluid into the atrium of the heart, the pleural lining of the lung, the gallbladder, and/or other suitable terminal locations. 
     The valve device  104  can be positioned between the proximal and distal portions  108   a - b  of the catheter  102  to regulate the body fluid flow through the drainage system  100 . As shown in  FIG. 1A , for example, the valve device  104  can be implanted in a subclavicular pocket of the patient  101 . In other embodiments, the valve device  104  can be installed in a prefascial or subfascial intra-abdominal region. This intra-abdominal positioning is particularly suited for neonates to ease exchange of the valve device  104  as the child grows, but also facilitates accessibility to the valve device  104  for adults. Advantageously, placement of the valve device  104  in either the subclavicular pocket or the intra-abdominal region negates the need to shave the patient&#39;s scalp to perform cranial surgery in the event that a component requires replacement or repair, and thus avoids the need for repeated incisions in the scalp that can cause devascularization, poor wound healing, and/or infection. The intra-abdominal valve device  104  also eases the periodic replacement of batteries or other power sources. In other embodiments, the valve device  104  can be installed subcutaneously in other regions of the torso or between another site of excess body fluid and a receptacle that can collect and/or reabsorb the body fluid. In further embodiments, the valve device  104  can be miniaturized such that it can be implanted under the scalp. 
     The sensors  106  can measure pressure within the catheter  102 , flow rate of the body fluid through the catheter  102 , and/or other desired measurements associated with body fluid drainage through the drainage system  100 . Pressure sensors can be small electrical sensors positioned along the drainage device  100 . Body fluid flow rate through the catheter  102  can be measured with a non-electrical Rotameter that uses a local or remote sensor to read the position of a weighted or buoyant ball that rises and falls within the catheter  102  in proportion to the flow rate. In other embodiments, the body fluid flow rate can be measured using what is known in the art as the “ice cube test.” An improved version of such a flow rate sensor includes a resistive electrical heater and temperature sensor embedded in the body fluid flow, rather than an external heater/cooler and an external temperature measurement device used in conventional ice cube tests. In further embodiments, body fluid flow rate can be measured using what is known as a “tick-tock chamber” that senses the rate that specialized chambers refill with the body fluid within the catheter  102 . 
     As shown in  FIG. 1A , the sensors  106  can be positioned proximate to the outlet and inlet to the valve device  104 . Accordingly, the first sensor  106   a  can measure the flow rate and/or the pressure within the proximal catheter  108   a  before it enters the valve device  104  and the second sensor  106   b  can measure the flow rate and/or pressure within the distal portion  108   b  as it exits the valve device  104 . This information can be used to ensure the valve device  104  generates the desired drainage rate, to monitor patient orientation, to perform diagnostics on the drainage system, and/or derive other desired measurements or characteristics. In other embodiments, the drainage system  100  can include more or less sensors  106 . For example, a pressure sensor  106  can be positioned proximate to the inlet region  116  to measure ICP directly. 
     The sensors  106  can also be used to derive a pressure at a desired location (e.g., the Foramen of Monroe for ICP) spaced apart from the sensors  106 . For example, the sensors  106  that are positioned proximate to the valve device  104  in the torso of the patient  101  can be used to derive ICP. As shown in  FIG. 1A , the sensors  106  can be positioned on either side of the valve device  104  to measure pressure upstream and downstream of the valve device  104 . When the patient  101  is upright (i.e., standing), the first sensor  106   a  at the proximal portion  108   a  can measure a pressure that is substantially equal to the ICP plus the pressure head created by the body fluid in the proximal portion  108   a  above the first sensor  106   a.  The second sensor  106   b  at the distal portion  108   b  can measure a pressure substantially equal to the pressure at the outlet region  118  (e.g., the peritoneal cavity  115 ; as is known in the art, the pressure is approximated as zero relative to atmosphere) plus the negative pressure created by the body fluid in the distal portion  108   b  below the second sensor  106   b . The pressures from the upstream and downstream sensors  106  can be combined to derive the true ICP. For example, when the valve device  104  is positioned midway between the ventricle  113  and the outlet region  118 , the summation of the two pressure measurements from the sensors  106  negates the contribution of pressure head and provides the true ICP. 
     In other embodiments, as described in greater detail below with reference to  FIGS. 7A-7D , a pressure reference line can be coupled to the drainage system  100  and used to compensate for changes in patient position. The pressure reference line measures the pressure head between a desired reference location and the sensor  106  at the valve device  104  directly. As such, the desired pressure measurement (e.g., ICP) is simply the difference between the two measured pressures as taken from two independent sensors (i.e., the pressure reference line sensor and the drainage line sensor) or a single differential pressure sensor. 
     The drainage system  100  can also include an orientation sensor (not shown) to accurately measure a desired pressure (e.g., ICP) regardless of the orientation of the patient  101 . For example, the orientation sensor can include an accelerometer, inclinometer, and/or other orientation sensing device. The orientation sensor is used to determine the angle of repose (i.e., standing, lying, or therebetween); such that the measured angle and the known length of the proximal portion  108   a  of the catheter  102  can be used to calculate the pressure head. The pressure head can be subtracted from the measured pressure to calculate the true ICP. 
     The controller  110 , e.g., a microprocessor, can read the measurements taken from the sensors  106  (e.g., pressure, flow rate, orientation, etc.), store such measurements and other information in a database, adjust the position of the valve device  104 , and/or carry out algorithms to regulate fluid flow through the drainage device  100 . For example, the controller  110  can compare pressure measurements from the sensors  106  with a desired ICP to determine whether to incrementally open or close the valve device  104  and by what percentage. For example, when the pressure is lower than a desired pressure, the controller  110  can incrementally close the valve device  104  to increase the resistance to antegrade flow through the catheter  102 . If the sensed pressure is higher than desired, the controller  110  can incrementally open the valve device  104  to decrease the resistance to antegrade flow. Similarly, the controller can also compare the sensed flow rate with a desired flow rate, and adjust the position of the valve device  104  accordingly. The controller  110  can also carry out an algorithm that moves the valve device  104  a predetermined amount each time a measurement outside of a desired limit (e.g., desired CSF range) is detected. Such a control algorithm can also relate the incremental movement of the valve device  104  to the magnitude of the difference between a desired and a measured value. In other embodiments, a proportional-integral-derivative (“PID”) control algorithm or variations thereof (e.g., P-only, PI-only) can control the movement of the valve device  104 . As such, the controller  110  can manage body fluid flow in real-time to maintain the ICP and/or other desired parameter within appropriate limits across a range of changes in pressure or body fluid generation rate caused by physiologic processes (e.g., valsalva maneuvers, changes in body orientation). 
     The controller  110  can include algorithms that save power. For example, a tolerance window on the control parameter (e.g., ICP or CSF flow rate) can be defined such that the valve device  104  does not change position within the tolerance window. As another example, the time between sensor measurements can be adjusted based on the error between the desired set point and the measured value, such that less frequent measurements are made during periods of small error. These power-saving control algorithms can also be adapted to the dynamics of the specific application. During CSF drainage, for example, significant changes in CSF production may occur over several hours such that only infrequent sensor measurements and valve device  104  movements are necessary for adequate flow control. As such, the controller  110  can be configured to ignore unimportant transient conditions (e.g., ICP oscillations due to the cardiac cycle, ICP increases due to coughing or movement) removed by averaging sensor measurements and/or frequency filtering. 
     Additionally, the controller  110  can also include logic to clear the valve device  104  of obstructions by incrementally opening the valve device  104  until the obstruction clears. For example, the controller  110  can be configured to maintain a desired ICP such that when an obstruction within the valve device  104  causes an increase in the measured pressure, the control algorithm (e.g., a proportional-integral-derivative) incrementally or fully opens the valve device  104  to decrease the resistance to antegrade flow. This incremental opening of the valve device  104  allows the obstruction to flow through the valve device  104  such that the drainage system  100  can maintain the desired ICP. As described in further detail below, in other embodiments, the controller  110  can include logic that clears and/or prevents obstructions by flushing the catheter  102  with body fluid. 
     As further shown in  FIG. 1A , the drainage system  100  can include a time keeping device  124  (e.g., clock, timer, etc.) that is operatively coupled to the controller  110 . The controller  110  can use the time keeping device  124  to sense pressure and/or flow rate at preset time intervals (e.g., once a minute). Additionally, as explained in further detail below, the controller  110  can use the time keeping device  124  to periodically flush the catheter  102  and/or periodically run diagnostics. 
     Additionally, as shown in  FIG. 1A , the drainage system  100  can also include a power source  122  for the valve device  104  and/or other electrical features (e.g., the time keeping device  122 , the sensors  106 , etc.). The power source  122  can be stored locally within the drainage system  100 . As such, the power source  122  can thus include a lithium-ion cell, a rechargeable battery, and/or other suitable portable power sources. In selected embodiments, the internally installed power source  122  can be recharged remotely using inductive coupling, kinetic energy generation by M2E of Boise, Id., and/or other remote recharging methods known in the art. In other embodiments, the drainage system  100  can connect to an external recharging station. 
     In selected embodiments, the controller  110  can be operatively coupled to a wireless communication link  126 , such as a WiFi connection, radio signal, and/or other suitable communication links that can send and/or receive information. The wireless communication link  126  allows measurements from the sensors  106  and/or other information to be monitored and/or analyzed remotely. For example, the wireless communication link  126  allows measurements recorded from the sensors  106  to be accessed at a doctor&#39;s office, at home by the patient  101 , and/or at other remote locations. Additionally, the drainage system  100  can use the wireless communication link  126  to receive information at a WiFi hot spot or other remotely accessible locations. This allows a remote physician to inquiry the drainage system  100  regarding particular measurements (e.g., ICP), instruct the controller  110  to adjust the valve device  104  accordingly, and/or program sophisticated algorithms onto the controller  110  for the drainage system  100  to carry out. Accordingly, the drainage system  100  can provide more expedient, sophisticated, and personalized treatment than conventional CSF shunts, without requiring frequent in-office visits. 
     As further shown in  FIG. 1A , the valve device  104 , the controller  110 , and/or other subcutaneously implanted features of the drainage system  100  can be enclosed within a housing  128 . Accordingly, the housing  128  can be made from a biocompatible material that protects the devices stored within from tissue ingrowth, body fluids, and/or other internal bodily features that may interfere with the operability of the drainage system  100 . In selected embodiments, the housing  128  can also form a magnetic shield over the devices within it such that the patient  101  can undergo magnetic resonance imaging (“MRI”) and similar procedures without removing the drainage system  100 . 
     In operation, the drainage system  100  can have generally low power consumption. For example, the drainage system  100  requires minimal, if any, continuous power. In one embodiment, the time keeping device  124  is the only feature of the drainage system  100  that continuously draws from the power source  122 . Other devices can draw from the power source  122  intermittently as needed. For example, the sensors  106  and/or other sensing devices can sense pressure at preset intervals (e.g., once per minute) and only draw from the power source  122  at that time. Similarly, any diagnostics and/or forced flows (e.g., backflushing, described below) only occur periodically and thus only require power occasionally. In selected embodiments, the valve device  104  only requires power when it changes position to adjust the pressure and/or flow rates. Without the need for any continuous substantial power, the drainage system  100  consumes much less power than would be required using a pump to drive body fluid. As described below, the drainage system  100  can also include a hybrid mechanical and electrical device that reduces the required frequency of actuator movements, and thus further reduces power consumption. Accordingly, the drainage system  100  can be configured such that the power source  122  runs the drainage system  100  for extended periods of time (e.g., five or more years), and therefore does not necessitate frequent surgeries to replace the power source  122 . 
     Optionally, the drainage system  100  can also include a pump (e.g., an electro-osmotic pump) that can be activated to drive body fluid flow through the drainage system  100 . For example, the controller  110  can include logic that activates the pump when the orientation of the patient  101  is such that the body fluid flows in the reverse direction (i.e., retrograde flow) through the catheter  102 . In other embodiments, the drainage system  100  can include other suitable devices and features that facilitate the controlled drainage of body fluids. 
     The subcutaneously installed drainage system  100  shown in  FIG. 1A  can also include features that limit the risk of infection during and after implantation. For example, components of the drainage system  100  (e.g., the catheter  102 , the housing  128 ) can include anti-fouling coatings and/or antibiotic impregnated materials. In selected embodiments, short-term thermal cooling and heating can be applied to the drainage system  100  as a whole or components thereof to reduce bacterial colonization during the perioperative period. In other embodiments, the housing  128 , the valve device  104 , and/or other portions of the drainage system  100  can be magnetized or otherwise treated to reduce bacterial growth and contamination. 
       FIG. 1B  is a schematic view of an external body fluid drainage system  150  (“drainage system  150 ”) implanted in the patient  101  in accordance with an embodiment of the present technology. The drainage system  150  includes features generally similar to the drainage system  100  described above with reference to  FIG. 1A . For example, the drainage system  150  can include the catheter  102  having the proximal portion  108   a  and the distal portion  108   b,  the valve device  104  positioned therebetween, the sensors  106 , and the controller  110  operatively coupled to the sensors  106  and the valve device  104 . Additionally, like the internal drainage system  100  described above, the external drainage system  150  can regulate CSF or other excess body fluid flow using sophisticated and individualized methods, and do so while operating as a low power system. However, the drainage system  150  shown in  FIG. 1B  is installed externally, between the ventricle  113  and an external receptacle  114 . The external receptacle  114  can be placed in fluid communication with the outlet region  118  of the catheter  102  such that it can collect the excess body fluid. As such, the external receptacle  114  can be a bag or container made from a range of polymers (e.g., silicone, polyvinyl chloride) and/or other suitable materials for storing body fluids. 
     In the illustrated embodiment, the external receptacle  114  is secured to the midsection of the patient  101  with a belt  120  such that the patient  101  can remain mobile as the drainage system  150  removes the excess body fluid. As shown in  FIG. 1B , the belt  120  can also carry the housing  128  that contains the valve device  104 , the controller  110 , and/or other devices that operate the drainage system  150 . The externally positioned housing  128  can be made from a durable material (e.g., plastic) that can withstand the rigors of the outside environment and substantially protect the components within. Snaps, thread, hooks, and/or other suitable fasteners can be used to secure the external receptacle  114  and/or the housing  128  to the belt  120 . In other embodiments, the external receptacle  114  and/or the housing  128  can be secured to other portions of the patient  101  that do not substantially inhibit the patient&#39;s mobility. 
     In further embodiments, such as when the drainage system  100  is used for temporary shunting of acute accumulation of the body fluid, the external receptacle  114  can be hung on a pole commonly used for IV bags or otherwise affixed to an external structure. Additionally, for temporary drainage, the devices within the housing  128  can also be positioned apart from the patient  101 , such as on a console connected with a power source. 
       FIG. 2A  is a schematic cross-sectional view of the valve device  104  for use with the body fluid drainage systems  100  and  150  shown in  FIGS. 1A and 1B  and configured in accordance with an embodiment of the present technology. As shown in  FIG. 2A , the valve device  104  can include an actuator  230  positioned over a portion of the catheter  102 . The actuator  230  can apply varying forces to the external surface  112  of the catheter  102  to regulate the body fluid flow rate therein. The surface with which the actuator  230  contacts the catheter  102  can vary in size and shape. For example, the contact surface can be flat, rounded, and/or have a different profile or shape. The contact surface can also vary in length along the axis of the catheter  102  to spread the force of the actuator  230  across the catheter  102 . For example, controlling drainage of CSF can be accomplished using contact lengths of a few millimeters to a few centimeters. 
     In the illustrated embodiment, the actuator  230  contacts one side of the catheter  102  to compress or “pinch” the catheter  102 . In other embodiments, the actuator  230  can apply force from opposing sides of the catheter  102  or apply force from multiple angles around the circumference of the catheter  102  to effectuate a similar compression or pinching action. This external compression eliminates the mechanical valve parts within the catheter  102 , and thus prevents the actuator  230  from coming into contact with the body fluid within the catheter  102 . Accordingly, the body fluid has a clear flow path through the catheter  102  that substantially reduces or eliminates stagnant flow regions (e.g., internal mechanical parts) and obstructions (e.g., build-up on the internal mechanical parts) often caused by the complex flow pathways common to conventional shunts. Additionally, in selected embodiments, the actuator  230  can be configured to fail in the open position (i.e., not restricting flow) such that it does not to impede drainage of the body fluid. 
     The actuator  230  can incrementally or continuously change the flow resistance of the catheter  102  to regulate drainage rate of the body fluid. For example, rather than a binary open-closed valve, the actuator  230  can compress the catheter  102  varying degrees between the open and closed positions. The actuator  230  can thus adjust the level of compression to accommodate a multitude of variables, and precisely regulate flow rate through the catheter  102 . For example, CSF drainage devices (e.g., the drainage devices  100  and  150  shown in  FIGS. 1A and 1B ) can vary the compression of the actuator  230  in response to the patient&#39;s orientation, a siphoning condition, ICP, retrograde flow, peritoneal pressure, and/or other variables that affect the desired flow rate. Thus, the valve device  104  provides sophisticated control of the body fluid drainage. 
     Advantageously, despite this precise control, the valve device  104  can also have generally low power requirements because the valve device  104  only requires power as it adjusts the position of actuators  230 . Once at a desired position, the actuator  230  can maintain its position without power (e.g., “self-braking”). Piezo-electric actuators (e.g., the Squiggle Motor by Newscale Technologies of Victor, N.Y.) include such incremental movement and self-braking features. Advantageously, piezo-electric actuators  230  can also be small, consume little power when they do move, but can also provide significant force on the catheter  102 . Piezo-electric actuators can also be compatible with MRIs. In selected embodiments, the valve device  104  can also be configured to permit fluctuation within a desired range (e.g., cardiac effects) and/or transient spikes or troughs (e.g., coughing) in pressure and/or flow rate. This prevents the actuator  230  from unnecessarily changing positions and unnecessarily consuming power. In other embodiments, the self-braking actuator  230  can be combined with a variable resistance component (e.g., a compliant interface member described in  FIGS. 3F-3H ) such that the valve device  104  can operate indefinitely without power as long as the pressure and/or flow rate remain within the desired limits. These reduced power features of the valve device  104  can be of particular advantage for internally implanted valve devices  104  (e.g., the drainage system  100  shown in  FIG. 1A ) because it increases the lifetime of the power source  122  between recharging cycles or surgeries to replace the power source  122 . 
     The actuator  230  can also be configured to close to prevent any undesired retrograde flow through the catheter  102 . For example, the sensors  236  can detect a pressure gradient directed toward the proximal portion  108   a  of the catheter  102  (e.g., toward the brain) that may be caused by patient orientation (e.g., upside-down), straining of the abdomen, low ICPs, and/or other conditions that may induce retrograde flow. In response to this negative pressure gradient, the controller  110  ( FIGS. 1A and 1B ) can close the actuator  230  to obstruct all flow through the valve device  104 . In other embodiments, flow sensors and/or pressure sensors positioned elsewhere along the drainage systems  100  and  150  can sense retrograde flow and trigger the closing of the actuator  230 . Alternatively, the valve device  104  can include a one-way check valve as a purely mechanical method to prevent retrograde flow such that monitoring for retrograde flow with the controller  110  is not required. 
     The force applied by each of the actuator  230  to the exterior surface  112  and/or the effect thereof can be monitored by sensors  236  (identified individually as a first pressure sensor  236   a  and a second pressure sensor  236   b ). As shown in  FIG. 2A , the sensors  236  can be positioned proximate to an inlet portion  238  and an outlet portion  240  of the valve device  104  to measure the pressure and/or flow rate within the catheter  102  before and after the body fluid exits the valve device  104 . The controller  110  can analyze these pressure or flow rate measurements to determine whether the valve device  104  produced a desired pressure or flow rate, and adjust the positions of the actuator  230  accordingly. In other embodiments, additional sensors  236  can be coupled to other portions of the catheter  102  to measure additional pressures, flow rates, and/or other desired properties of the flow through the valve device  104 . 
     The actuator  230  and the sensors  236  can also be used to diagnose flow problems in the catheter  102 . For example, the actuator  230  can be closed, and the pressure response can be measured over time and compared to an expected pressure for unobstructed flow, to the expected time required for the pressure to return to a baseline value, and/or to other pressure related values that can interpret fluid flow. Closing the actuator  230  during unobstructed flow results in a generally rapid increase in the pressure measurement upstream of the valve device  104 , and opening the actuator  230  results in a rapid decrease in the pressure measurement as fluid freely flows through the distal portion  108   b  of the catheter  102 . Little or no pressure increases observed upon closing the actuator  230  indicates an obstruction in the proximal portion  108   a,  while a slow decrease in pressure upon opening the actuator  230  indicates an obstruction in the distal portion  108   b.  These flow diagnostics can be performed routinely to sense obstructions at their onset. Additionally, the valve device  104  can be configured to perform these diagnostic tests more frequently when the potential for obstructions is higher (e.g., after surgery). 
     In other embodiments, diagnostics can be performed during normal operation (i.e., no specialized movement and no forced flow) of the drainage systems  100  and  150 . For example, when the valve device  104  uses pressure-based control to maintain a constant pressure (e.g., ICP), an actuator  230  consistently operating at a fully-open position can indicate a blocked valve device  104  or an obstructed distal portion of the catheter  102 . Conversely, an actuator  230  consistently operating in a fully-closed position can indicate an obstructed proximal portion  108   a  of the catheter  102 . 
     In other normal operation flow diagnostics, pressure levels within a patient can be tracked (e.g., remotely via the wireless communications link  126  shown in  FIGS. 1A and 1B ) and characterized as “acceptable” or “unacceptable” pressure levels. In the case of a CSF drainage system, for example, an unacceptable level may be one that induces a headache. Using this information, the controller  110  can adjust the valve device  104  to maintain acceptable ranges of pressure for the particular patient. Thus, the diagnostic control of the valve device  104  can provide precise and individualized treatment to ensure not only that the excess body fluid is adequately drained, but also adjust to the particularities of each patient&#39;s needs. 
     In other embodiments, flow rate measurements, rather than or in conjunction with pressure measurements, can also be used to perform diagnostic tests and diagnose blockages. Similar to the pressure sensor driven diagnostics, Rotameters, the “ice cube test,” the tick-tock chamber, and/or other flow rate sensors can measure flow rate during forced or unforced flow and compare it with a desired flow rate to identify partial or complete blockages. 
     In other embodiments, the valve device  104  can include more than one actuator  230 . For example, the valve device  104  can include multiple actuators  230  to provide redundancy in the event an actuator  230  fails. Additionally, the inlet and outlet portions  238  and  240  can include multiple actuators  230  in order to vary the location of constrictions. This allows the actuators  230  to constrict alternate portions of the catheter  102  when others have debris build up. In further embodiments, selected actuators  230  can be designated solely to close the catheter  102  to obstruct antegrade flow. Other actuators  230  can adjust continuously between the open and closed positions to regulate flow rate as described above. 
       FIG. 2B  is a schematic cross-sectional view of a valve device  204  in accordance with another embodiment of the disclosure. The valve device  204  includes features generally similar to the valve device  104  shown in  FIG. 2A . For example, the valve device  204  includes the sensors  236  and the incrementally adjustable actuator  230  at the exterior surface  112  of the catheter  102 . However, the valve device  204  shown in  FIG. 2B  includes additional actuators  230  (identified individually as a first actuator  230   a,  a second actuator  230   b,  and a third actuator  230   c ) positioned over different portions of the catheter  102 . One or more of the actuators  230  can provide the incremental force at the exterior surface  112  of the catheter  102  in order to regulate flow and/or include power-saving self-braking features. Accordingly, like the valve device  104  shown in  FIG. 2A , the valve device  204  can provide sophisticated flow control, but also benefit from the low power consumption described above. Additionally, the position of each actuator  230  can be adjusted independently by the controller  110  to produce the desired flow rate of the body fluid through the catheter  102 . 
     In the embodiment illustrated in  FIG. 2B , the valve device  204  further includes a reservoir  232  positioned between the proximal and distal portions  108   a - b  of the catheter  102 . The reservoir  232  and the proximal and distal portions  108   a - b  can include generally similar materials and can be formed integrally or sealed together with adhesives and/or other fasteners that provide a liquid-tight seal. As shown in  FIG. 2B , the reservoir  232  can have an exterior surface  234  and a larger cross-sectional dimension than a cross-sectional dimension of the catheter  102  such that the reservoir  232  retains a larger volume of the body fluid per cross-section than the catheter  102 . In the illustrated embodiment, the proximal portion  108   a,  the reservoir  232 , and the distal portion  108   b  can form a single lumen through which the body fluid can flow. This singular lumen provides a simple flow path for the body fluid that can reduce or eliminate obstruction-prone areas (e.g., corners, intersections between lumens) that exist in more intricate flow paths. 
     The reservoir  232  allows the valve device  204  to create forced flow or “flushing” through the proximal and distal portions  108   a - b  of the catheter  102  to clear obstructions within the catheter  102  and/or enable diagnostics of flow obstructions. For example, the valve device  204  can compress the reservoir  232 , and the controller  110  or remote device can interpret pressure and/or flow rate changes of the forced flow to identify partial or complete blockages. The valve device  204  can also periodically evacuate the reservoir  232  toward the proximal and/or distal portions  108   a - b  of the catheter  102  to break up any build up within the catheter  102 , and thereby reduce the likelihood of obstructions. The flow diagnostics and flushing can be performed routinely sense and remove obstructions at their onset. The valve device  204  can also perform diagnostic tests more frequently when the potential for obstructions is higher (e.g., after surgery). 
     In the illustrated embodiment, the third actuator  230   c  contacts a large portion of the exterior surface  234  of the reservoir  232  such that it more rapidly accelerates the volume of body fluid out of the reservoir  232 . For example, as shown in  FIG. 2B , the reservoir  232  has a first length L 1  and the third actuator contacts the exterior surface  234  of the reservoir  232  along a second length L 2  that is substantially equal to the first length L 1 . This increased contact area provides a greater forced flow that can be used to remove obstructions (e.g., protein build up), run diagnostics, or otherwise flush the catheter  102  with the body fluid. In selected embodiments, the third actuator  232   c  can linearly apply force to the reservoir  232  along the second length L 2  to push the body fluid in a desired direction (e.g., toward the proximal portion  108   a  or the distal portion  108   b ). In other embodiments, the backflushing and/or forward flushing can be performed manually by the patient or caregiver by pressing on the reservoir  232  and directing the body fluid in the desired direction. The backflushing, forward flushing, and diagnostic operations can be performed either in an implantable drainage system  100  or an external drainage system  150 . 
     The valve device  204  shown in  FIG. 2B  can also be used in conjunction with a conventional valve to add flushing and diagnostic operations (e.g., with flow regulation provided fully or partially by the conventional valve). For example, to retrofit the conventional drainage system, the valve device  204  can be placed in fluid communication with a conventional valve device (e.g., a mechanical ball in seat valve device). The valve device  204  can then adjust the actuators  230  to generate forced flow and/or incrementally regulate fluid flow. If only forced flow is desired, the valve device  204  need only include the reservoir  232  and one or more binary actuators that can accumulate body fluid in the reservoir  232  and expel it periodically as desired. As such, forced flow diagnostics can be performed periodically on the conventional drainage system to detect obstructions in the flow path of the body fluid. For example, the reservoir  232  can flush a portion of the conventional system, and the pressure response can be compared with the pressure and/or pressure decay of an unobstructed flow path. When used with a separate valve, the pressure response can be used to test the pressure-flow characteristics of the conventional valve to monitor its degradation over time. Alternatively, the flow rate can be monitored to detect obstructions and/or monitor the degradation of the conventional valve device. 
       FIGS. 3A-3J  are side views of actuators for a body fluid drainage system (e.g., the drainage systems  100  and  150  shown in  FIGS. 1A and 1B ) in accordance with embodiments of the present technology. Each of the actuators shown in  FIGS. 3A-3J  are pinch actuators that are incrementally and/or continuously adjustable between the open and closed positions. Therefore, as described above, the actuators can compress the catheter  102  and/or the reservoir  232  ( FIG. 2B ) to incrementally regulate body fluid flow.  FIG. 3A , for example, shows a linear actuator  360  that can move in the directions indicated by the arrows to incrementally compress the catheter  102 , and thereby change the resistance within the catheter  102 . Any of the embodiments described below can be combined, can include interface members that transfer force from the actuator to the catheter  102 , and/or can include other types of actuators, interface members, and/or compliant interface members that incrementally compress the catheter  102 . 
       FIGS. 3B-3E  illustrate embodiments of rotary actuation. For example,  FIG. 3B  illustrates a cam actuator  362  that compresses the catheter  102  by adjusting the amount of its rotation along the catheter  102 .  FIG. 3C  shows a lever actuator  366  that transmits force to an interface member, such as a contact pad or a contact roller  364 . As indicated by the arrows, the lever actuator  366  can rotate about a fulcrum to vary the degree at which the contact roller  364  compresses the catheter  102 . In the embodiment shown in  FIG. 3D , the linear actuator  360  of  FIG. 3A  rotates a lever  367  (i.e., the interface member contacting the catheter  102 ) about the catheter  102  to incrementally increase the resistance within the catheter  102 . As shown in  FIG. 3E , another rotary actuator, a screw actuator  369 , can rotate in one direction to apply more force to the catheter  102  and rotate in the opposite direction to release force on the catheter  102 . 
     In some embodiments, variable flow resistance may be created by compressing a region of the catheter via external means, but the actuator may be controlled by one or more mechanical levers. In one embodiment, for example, one end of a lever contacts a region of the shunt and moves in response to the pressure in the shunt, and another end of the lever contacts the valve region, in which an increase in pressure received by one end of the lever causes the other end of the lever to increase or decrease the opening in the valve region to change resistance to flow. The lever ends can directly contact the shunt tubing, which is flexible, or the lever ends can contact reservoirs with flexible diaphragms. The flow regulation characteristics may be set by the length of lever arms on either side of a fulcrum. The flow characteristics can be further set by the relative area of the shunt contacted by the lever contact points, such as by the size of flexible diaphragms that transmit to/from the lever arms. The flow regulation characteristics may be further set by adding springs or other force-generating means to one or more of the lever arms (see, e.g., the springs  332   a  and  332   b  of  FIGS. 3I and 3J , respectively). The lever mechanism can be a single lever or multiple levers. The mechanism can provide pressure or flow regulation. The mechanism can also be arranged to close the valve in response to a low pressure condition at the outlet to prevent siphoning. One feature of this valve design is that all mechanical components are external to the shunt, so fluid does not contact the mechanical valve components. This arrangement is expected to prevent fouling of the mechanism (which can cause failure in shunts with internal mechanical components), and the fluid path is greatly simplified compared to a number of alternative shunt valve designs (i.e., it reduces flow dead spots that may lead to fouling). 
       FIGS. 3F-3H , for example, show actuators that include a compliant interface member between the linear actuator  360  shown in  FIG. 3A  and the catheter  102 . In other embodiments, the actuators shown in  FIGS. 3F-3H  can use rotary or other types of actuation. Referring to  FIG. 3F , the compliant member can include a spring  368  or other compliant material that transmits force from the actuator  360  to the catheter  102  to control flow. As shown in  FIGS. 3G and 3H , the compliant member can also include a spring lever or other flexible lever  370  that rotates about a fulcrum  371  at the catheter  102 . In the embodiment illustrated in  FIG. 3G , the actuator  360  presses down on the flexible lever  370  to rotate it varying degrees and transmit the force from the actuator  360  to the catheter  102 . In the embodiment illustrated in  FIG. 3H , the actuator  360  can apply force upward against the flexible lever  370  such that it rotates and transfers force from the actuator  360  to the catheter  102 . In operation, the spring  368 , the flexible lever  370 , and/or other compliant interface members provides a degree of passive actuation that adjust the force applied to the catheter  102  without moving the actuator  360 . Accordingly, body fluid drainage systems (e.g., the drainage systems  100  and  150  shown in  FIGS. 1A and 1B ) including passive actuators can consume less power. 
       FIGS. 3I and 3J  show purely mechanical actuators that require no power to operate. For example,  FIG. 3I  shows an actuator  330  that can regulate the flow rate through the catheter  102 . The actuator  330  can include actuator contacts  335  (identified individually as a first actuator contact  335   a  and a second actuator contact  335   b ) connected to one another by a lever arm  331  having a first lever arm portion  331   a  and a second lever arm portion  331   b.  The desired flow rate characteristics of the actuator  330  can be obtained by changing the relative lengths of the first and second lever arm portions  331   a - b  and the relative areas of the first and second actuator contacts  335   a - b . As shown in  FIG. 3I , when the upstream pressure increases, the force on the first actuator contact  335   a  increases. The lever arm  331  transmits this force to the second actuator contact  335   b  such that it compresses the catheter  102 . The force on the catheter  102  increases the valve resistance, and thereby maintains an approximately constant flow rate through the valve device without requiring any power. 
       FIG. 3J  shows an actuator  333  that can regulate the upstream pressure in the catheter  102 . Similar to the actuator  330  shown in  FIG. 3I , the actuator  333  includes the actuator contacts  335  and the lever arm  331 . However, the lever arm  331  shown in  FIG. 3J  is bent or otherwise twisted such that the actuator contacts  335  act on opposing sides of the catheter  102 . The desired upstream pressure can be obtained by manipulating the relative lengths and areas of the lever arms  331  and the actuator contacts  335 . As shown in  FIG. 3J , when the upstream pressure increases, the force on the first actuator contact  335   a  increases. The lever arm  331  transmits the force to the second actuator contact  335   b  such that it removes force from the catheter  102 . This increases the opening of the catheter  102 , and thus decreases the valve resistance to relieve the pressure buildup. In selected embodiments, the actuators  330  and  333  shown in  FIGS. 3I and 3J  can also be configured to prevent retrograde flow. In further embodiments, multiple interacting lever arms  331  and actuator contacts  335  can be combined to enhance flow and/or pressure control. Additionally, the mechanical actuators can be assisted by electrically-powered actuators to provide a more sophisticated control with lower power draw. 
     In other embodiments, other devices or methods that compress or otherwise constrict the catheter  102  and/or the reservoir  232  can be used to control flow rate. For example, the catheter  102  can be twisted incrementally about its longitudinal axis to create a variable resistance. As another example, the catheter  102  can be wound (e.g., either a partial turn or many turns) around a shaft or other solid object, and the catheter  102  can then be stretched to create tension that causes variable flow through the catheter  102 . The catheter  102  can also be turned back on itself varying degrees to form one or more pinch points that can incrementally adjust flow rate. This actuation method can be advantageous because it can provide a level of passive activation, requires low force to vary the flow therein, and thus has a low power requirement. 
       FIGS. 4A and 4B  are side and perspective views, respectively, of reservoirs  432  for a body fluid drainage system (e.g., the drainage systems  100  and  150  shown in  FIGS. 1A and 1B ) in accordance with embodiments of the present technology. As shown in  FIG. 4A , the reservoir  432  can include a tubular body  472  that has a larger cross-sectional area than the catheter  102  to which it connects. The tubular body  472  can be formed integrally with the catheter, and can therefore include the same material as the catheter  102 . In other embodiments, the tubular body  472  can include materials that are different from those of the catheter  102 . For example, the tubular body  472  can include a compliant material that is too elastic for the entire length of the catheter  102 , but can advantageously expand to hold a desired volume of the body fluid within the reservoir  232 . 
     As shown in  FIG. 4B , the reservoir  432  includes a chamber  474 . The chamber  474  shown in  FIG. 4B  has a generally flat, rectangular shape, but can have other suitable shape (e.g., spherical, cylindrical) for the reservoir  424 . In selected embodiments, the chamber  474  can include a less compliant material than the catheter  102 , but can also include one or more compliant regions that can be compressed by the actuator  360 . In other embodiments, the reservoir  432  can have other suitable configurations that can contain a greater cross-sectional volume than the catheter  102 . 
       FIGS. 5A-5D  are schematic, cross-sectional top plan views of body fluid flow through the valve device  204  of  FIG. 2B  in accordance with an embodiment of the present technology.  FIG. 5A , for example, shows the valve device  204  with all actuators  230  in an open position to provide unobstructed antegrade flow through a valve device  204 . As shown in  FIG. 5B , select actuators  230  can apply force against the exterior surface  112  of the catheter  102  to slow the flow rate of the body flow. More specifically,  FIG. 5B  shows the first actuator  230   a  in an intermediate position (i.e., between fully open and fully closed) that partially obstructs antegrade flow through the proximal portion  108   a  of the catheter  102 . The second actuator  230   b  is also in an intermediate position, but applies a greater force to the exterior surface  112  of the catheter  102 . Partially closed actuators  230  can be of particular advantage to prevent siphoning of the body fluid. Any adjustment (e.g., partially closed, closed, or open) of the actuators  230  can occur successively or in tandem. 
     The valve device  204  can also adjust to force antegrade flow and retrograde flow to “flush” the catheter  102  with the body fluid. As shown in  FIG. 5C , for example, the second actuator  230   b  can be closed to stop fluid flow through the distal portion  108   b  of the catheter  102 , and the third actuator  230   c  can compress the reservoir  232  to evacuate the body fluid collected therein. This forces the body fluid through the open first actuator  230   a  into the proximal portion  108   a  of the catheter  102 , and thereby clears obstructions and loosens build up of blood, cellular debris, postoperative debris, and/or other debris within in the proximal portion  108   a  and/or the inlet region of the catheter  102 . 
     Similar to the backflushing shown in  FIG. 5C , the valve device  204  can also adjust to provide a forward flush. For example, as shown in  FIG. 5D , the first actuator  230   a  can close to stop fluid flow above it, and the third actuator  230   c  can compress the reservoir  232  to force the body fluid through the distal portion  108   b  of the catheter  102 . This forced flow provided to either the proximal or distal portions  108   a - b  of the catheter  102  can dislodge obstructions (e.g., blood, cellular debris, postoperative debris) in the catheter  102  and disrupt tissue invasion that may occur at the inlet or outlet regions (not shown) of the catheter  102 . 
     In selected embodiments, the valve device  104  can perform periodic backflushing and forward flushing to reduce the likelihood of obstructions. The periodic forced flow can also be used in conjunction with the diagnostic tests described above. In other embodiments, the backflushing and/or forward flushing can be performed manually by the patient or caregiver by pressing on the reservoir  232  and directing the body fluid in the desired direction. 
       FIGS. 6A and 6B  are illustrations of antegrade flow and retrograde flow, respectively, through the inlet region  116  of the body fluid drainage systems  100  and  150  of  FIGS. 1A and 1B  described above in accordance with an embodiment of the present technology. In the illustrated embodiment, the inlet region  116  is inserted into the lateral ventricle  113  such that the drainage systems  100  and  150  can remove excess CSF fluid. As shown in  FIG. 6A , the inlet region  116  of the catheter  102  can include a plurality of openings  676  through which excess CSF can enter the drainage systems  100  and  150 . As shown in  FIG. 6B , the CSF can be directed in retrograde flow via the valve device  104 . For example, the valve device  104  can be configured as shown in  FIG. 5C  to force flow through the proximal portion  108   a  of the catheter  102 . This can expel CSF out of the openings  676  and clear the inlet region  116  of obstructions. For example, as shown in  FIG. 6B , the inlet region  116  can be obstructed with choroid plexus ingrowth, ependymal lining ingrowth, and/or other tissue ingrowth  617 . The forced retrograde flow of CSF can mobilize an ingrown portion  678  such that it no longer blocks the openings  676  of the inlet region  116 . In other embodiments, the valve device  104  can force antegrade flow through the distal portion  108   b  of the catheter to reduce the likelihood of tissue ingrowth or other obstructions at the outlet region  118  (not shown) of the catheter  102 . 
       FIG. 7A  is a partial schematic view of a body fluid drainage system  700  (“drainage system  700 ”) in accordance with a further embodiment of the present technology, and  FIGS. 7B-7D  show enlarged portions of the drainage system  700  of  FIG. 7A . The drainage system  700  can include features generally similar to the external drainage system  150  described above with reference to  FIG. 1B . For example, the drainage system  700  can include a catheter  702  that has a proximal portion  708   a  at the source of excess body fluid and a distal portion  708   b  that drains the excess body fluid to an external receptacle  714 . In other embodiments, the drainage system  700  can discharge the excess body fluid to an internal receptacle, such as described above with reference to  FIG. 1A . As shown in  FIG. 7C , the drainage system  700  can also include a valve device  704  that applies forces to the exterior of the catheter  102  to regulate the drainage of the body fluid. 
     As shown in  FIG. 7A , the drainage system  700  further includes a pressure reference line  780  (“reference line”) and a controller interface  782 . Both can be coupled to a controller  710  ( FIG. 7C ) that has generally similar features as the controller  110  described above. The reference line  780  can include a fluid-filled tube that extends between a flexible end cap  787  at a first end portion  781   a  and a pressure sensor  784  at the second end portion  781   b.  In a CSF drainage system, the fluid that fills the reference line  780  can be a silicone oil or other fluid that has a density substantially equal to CSF. In other embodiments, the reference line  780  can include a fluid that has a density substantially equal to the body fluid being drained. In further embodiments, the reference line  780  can be filled with a fluid that has a density different from the body fluid being drained, and the differing densities can be accounted for in an associated algorithm. 
     As shown in  FIG. 7B , the end cap  787  can include a flexible silicone balloon, bag, and/or other flexible structure  789  and a protective cage or barrier  791 . The barrier  791  can prevent accidental compression of the flexible structure  789  and can be vented to allow pressure communication with the environment external to the barrier  791 . For an implantable device, the barrier  791  can be designed to prevent body tissue from interacting with the flexible structure  789 . In one embodiment, the end cap  787  has a diameter of a few millimeters and a length of approximately 1 cm to discretely fit over the patient&#39;s ear as shown in  FIG. 7A . In other embodiments, the end cap  787  can have larger or smaller dimensions to accommodate its placement. 
     To obtain a desired pressure, the end cap  787  can be positioned proximate to the desired pressure measurement, and the pressure sensor  784  can be placed in fluid communication with the catheter  702  (i.e., the drain line). For example, in the illustrated embodiment, the end cap  787  is mounted proximate to the Foramen of Monroe to measure ICP, and the pressure sensor  784  is placed in fluid communication with the catheter  702 . The difference between the pressure in the reference line  780  and the pressure of the catheter  702 A can be determined using a differential pressure sensor and/or two independent pressure sensors. This differential pressure measurement incorporates a direct measurement of the pressure head caused by the body fluid in the catheter  702 . Thus, the differential pressure measurement is equal to the pressure of the drainage system  700  at the end cap  787  (e.g., ICP). Advantageously, this direct measurement of the pressure head allows the reference line  780  to automatically compensate for positional changes of the pressure sensor  784  and the valve device  704  to which it is coupled. Therefore, the drainage system  700  can derive an accurate pressure measurement regardless of movement of the patient  701  and/or the valve device  704 . Accordingly, the drainage system  700  measures ICP more accurately than conventional CSF drainage systems that require the patient  701  to remain motionless during drainage procedures. 
     As shown in  FIG. 7C , the proximal portion  708   a  of the catheter  702  and the second end portion  781   b  of the pressure reference line  780  can extend into a cartridge  783 . The cartridge  783  can also house the pressure sensor  784  of the pressure reference line  780 , a flow rate sensor  784 , and/or other pressure and flow rate sensors (not shown) that contact CSF or other body fluids. In other embodiments, the pressure sensors and flow sensors can measure pressure and flow rate through the wall of the catheter  702  such that they do not contact the body fluid. Additionally, as shown in  FIG. 7C , the cartridge  783  can also include an electrical connection  785  that couples the drainage system  700  to a power source (not shown). 
     In selected embodiments, the cartridge  783  is disposable such that it can be coupled to reusable portions of the drainage system  700  that do not contact the body fluid. For example, as shown in  FIG. 7C , the disposable cartridge  783  can be coupled with the controller  710  and the valve device  704 . In selected embodiments, the disposable cartridge  783 , the reusable controller  710 , and/or other reusable components can be designed with registration features and positive engagement mechanisms such that they can only be assembled with the proper geometry. As such, the portions of the drainage system  700  that are contaminated with body fluid (i.e., the portions stored within the cartridge  783 ) can be thrown out after use, while the controller  710 , the valve device  704 , and other more intricate devices (e.g., flow sensors) can be conserved and used with a plurality of disposable cartridges  783 . 
       FIG. 7D  shows of the controller interface  782  of the drainage system  700  of  FIG. 7A . The controller interface  782  can include one or more user controls  786  (identified individually as a first user control  786   a  and a second user control  786   b ) and displays (identified individually as a first display  788   a  and a second display  788   b ), both operatively coupled to the controller  710 . The user controls  786  can allow a user (e.g., a medical professional) to select and adjust the desired condition for pressure or flow rate, as well as the tolerances of the drainage system  700 . For example, as shown in  FIG. 7D , the user controls  786  can change the desired ICP and/or flow rate of the drainage system  700 . The user controls  786  can be coupled to the controller  710  such that the controller  710  can adjust the valve device  704  to output the selected ICP or flow rate. The displays  788  can show the actual measured ICP and drainage rate to ensure the drainage system  700  meets the selected tolerances. Additionally, as shown in  FIG. 7D , the controller interface  782  can also include a warning signal  790  (e.g., a light, a bell) that activates when conditions do not allow proper drainage. For example, the warning signal  790  can be a light that illuminates when the external receptacle  714  is positioned too high relative to the rest of the drainage system  700 . 
       FIGS. 8A and 8B  are schematic views of body fluid drainage systems  800  and  850  installed in a CSF system  819  in accordance with additional embodiments of the present technology. The body fluid drainage systems  800  and  850  can include generally similar features as the drainage system  700  described above with reference to  FIGS. 7A-7D . For example, the body fluid drainage systems  800  and  850  include a pressure reference line  880  mounted over the equivalent external location of the Foramen Monroe to automatically account for movement of a patient  801  and/or an external receptacle (not shown). 
     As shown in  FIGS. 8A and 8B , the drainage systems  800  and  850  can drain CSF from different portions of the CSF system  819 . For example, in the embodiment illustrated in  FIG. 8A , the body fluid drainage system  800  includes a catheter  802  that has a proximal portion  808   a  inserted into the upper portion (e.g., a ventricle) of the CSF system  819 . Similar to the drainage systems  100 ,  150 , and  700  shown in  FIGS. 1A, 1B, and 7A-7D , the cranially inserted body fluid drainage system  800  can drain fluid through a distal portion  808   b  of the catheter  102  to an external receptacle or internal cavity. 
     The body fluid drainage system  850  shown in  FIG. 8B  includes a catheter  892  inserted into the patient&#39;s lumbar region the lower portion of the CSF system  819 . Similar to the cranially inserted drainage system  800  described above, the body fluid drainage system  850  can drain body fluid (e.g., CSF) from a proximal portion  894   a  of the catheter  892  to a distal portion  894   b  that is in fluid communication with an external receptacle or internal reabsorbtion cavity. Advantageously, despite the different insertion points of the body fluid drainage systems  800  and  850 , the pressure reference line  880  can still adjust for movement of the patient  801  to allow for accurate ICP measurements. 
     From the foregoing, it will be appreciated that specific embodiments of the present technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the disclosure. For example, the pressure reference lines  780  and  880  shown in  FIGS. 7A-8B  can be added to the body fluid drainage systems  100  and  150  shown in  FIGS. 1A and 1B . Additionally, the pressure reference lines  780  and  880  can be implanted in a patient, rather than externally mounted as in  FIGS. 7A-8B . Aspects of the disclosure described in the context of particular embodiments may be combined or eliminated in other embodiments. For example, the valve device  104  shown in  FIG. 2A  can include additional actuators that control body fluid flow through the catheter  102 . Further, while advantages associated with certain embodiments of the disclosure have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the disclosure. Accordingly, embodiments of the disclosure are not limited except as by the appended claims.