Preferably, such a system would use a multi-component pressure-kinetic model to determine the pressure compensation required due to a differential pressure between the inlet and outlet of the cassette pump. Such a system would preferably use real-time measurements of pressure at both the pump inlet and pump outlet to determine the differential pressure, and then use an empirically determined algorithm to determine the extent to which the position of the plunger should be adjusted to either increase or decrease the delivery pressure.
The delivery rate can further be optimized by changing the rate of the pumping cycles as a function of the actual volume delivered during each pump cycle. Preferably such a model would be used to pressure compensate the delivery of medicinal fluids for single or multi-channel cassette pumps.
It will thus be apparent that accurately controlling the administration of medicinal fluids under varying pressure conditions using a pressure compensation model would provide significant advantages over the prior art. In accord with the present invention, a pressure compensated pump is defined for maintaining an accurate delivery of fluid to a patient when a differential pressure exists between an inlet and outlet of the pump.
The pump includes a fluid drive unit that is adapted to couple with a fluid line and to force fluid from a source for infusion into the patient through the fluid line.
A control unit is coupled to the fluid drive unit to control its operation. A first pressure sensor monitors the inlet pressure to the pump, and a second pressure sensor monitors the outlet pressure of the pump. Both the first and the second pressure sensors are electrically coupled to the control unit. The control unit is programmed to determine a differential pressure between the inlet and the outlet of the pump, and the control unit uses an algorithm stored in a memory to determine a correction factor to be applied to compensate for the differential pressure between the inlet and the outlet, thus ensuring accurate delivery of the fluid to the patient.
In addition to correcting for pressure differences across the valves of the pump, the algorithm can include a correction factor that compensates for calibration differences between multiple pressure sensors, as well as a correction factor that compensates for differences between targeted intake fluid volumes and an actual intake fluid volumes, as well as for differences between targeted delivery fluid volumes and actual delivery fluid volumes.
Preferably, the control unit includes a microprocessor responsive to program steps stored in a memory included in the control unit.
The algorithm used to determine the correction factor is empirically determined. In a preferred embodiment, the fluid drive unit includes an elastomeric membrane overlying a chamber in the pump. The chamber is in fluid communication with the source and the patient. A driven member that is coupled to a motor exerts a force on the elastomeric membrane, displacing it into the chamber, thereby causing fluid to be expelled from the chamber into the patient.
The correction factor determined by the algorithm is expressed as a position of the driven member relative to the elastomeric membrane. In this embodiment, the corrected position of the driven member relative to the elastomeric membrane that is determined by the algorithm corresponds to a corrected position for the driven member at the start of a pump cycle, i.
When the control unit determines that the pressure at the outlet of the pump is greater than the pressure at the inlet, the control unit advances the driven member into the chamber to a position determined by the algorithm, and when the control unit determines that the pressure at the outlet is lower than the pressure at the inlet, the control unit retracts the driven member away from the chamber to a position determined by the algorithm. In either case, the driven member is always in contact with the elastomeric membrane during any segment of a pump cycle.
The algorithm employs a first lookup table in which a first value is indicated as a function of a pressure measured by the sensor monitoring the inlet pressure, and a second lookup table in which a second value is indicated as a function of a pressure measured by the sensor monitoring the outlet pressure. The correction factor is determined by combining the first value and the second value obtained from the first and second lookup tables.
The lookup tables are preferably empirically determined. The algorithm preferably uses a pressure measured by the sensor monitoring the outlet pressure after the driven member has exerted a force on the elastomeric membrane and the fluid has been displaced and forced into the fluid line toward the patient, in determining the correction factor for the next pump cycle. After the driven member has exerted a force on the elastomeric membrane and the fluid is forced from the chamber, the control unit uses the algorithm to determine the actual fluid volume delivered to the patient, and then calculates a correction factor that determines how the timing of the next pump cycle is to be modified to maintain a desired delivery rate of the fluid to the patient.
The pump preferably includes an inlet valve and an outlet valve. The correction factor that corresponds to a difference between a targeted intake fluid volume, and an actual intake fluid volume is determined by sampling a first pressure proximate the inlet port after the chamber has been filled with the targeted intake volume by moving the driven member to a first position, and then moving the driven member to a second position, such that the volume of the chamber is decreased.
The inlet pressure sensor determines a second pressure proximate the inlet port that exceeds the first pressure proximate the inlet port by a predetermined amount. The algorithm determines the actual intake fluid volume as a function of the first pressure proximate the inlet port, the second pressure proximate the inlet port, the first position of the driven member, and the second position of the driven member; and determines a difference between the targeted intake fluid volume and the actual intake fluid volume.
Preferably, the predetermined amount is about 1 psi. The difference between the targeted intake fluid volume and the actual intake fluid volume is used to increase the accuracy of the fluid infusion by adding the difference between the targeted intake fluid volume and the actual intake fluid volume to a targeted intake fluid volume of a subsequent pump cycle.
Preferably, the functional relationships between the intake fluid volume, the proximate pressure, and the position of the driven member are empirically determined. The algorithm can compensate for calibration differences between an inlet pressure sensor and an outlet pressure sensor. The steps employed to accomplish this function include opening the inlet valve while the outlet valve is closed, thus filling the pumping chamber with fluid, and closing the inlet valve when the chamber is filled with a desired volume of fluid.
The next step determines a pressure proximate the inlet port and a pressure proximate the outlet port using the inlet and outlet pressure sensors.
A position of the elastomeric membrane is adjusted such that a pressure of the fluid within the chamber is equivalent to the pressure proximate the outlet port; and the outlet valve is then opened. Next, the outlet pressure sensor is used to determine if a pressure spike accompanies the opening of the outlet valve the pressure spike being indicative of a calibration difference between the inlet pressure sensor and the outlet pressure sensor.
The pressure spike is used by the algorithm to compensate for the calibration difference in the next pump cycle. In an alternate embodiment, the pump includes only a pressure sensor in fluid communication with an outlet side of the pump, and a first pump cycle is uncompensated. Two outlet pressure readings are taken during each cycle—one at a beginning of the pump cycle when the chamber is full of fluid, and one just as the fluid is finishing being expelled from the chamber.
In the next pump cycle, the position of the driven member is adjusted relative to the chamber to compensate for any differential pressure between the two readings taken in the previous pump cycle. Another aspect of the present invention is directed to a method that includes steps generally consistent with the functions implemented by the components of the apparatus described above. A further aspect of the present invention is directed to an algorithm that includes steps also generally consistent with the description set forth above.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:. The present invention employs an algorithm to compensate for a differential pressure between the inlet and outlet of a cassette type infusion pump to enhance the accuracy of the pump, particularly at low flow rates.
The algorithm used in this embodiment has been empirically determined for these specific products. However, it should be noted that a similar algorithm can be empirically determined for other designs of infusion cassettes and infusion pumps. The present invention is thus not in any way limited to the specific design of the pump and cassette discussed below.
The plurality of samples are averaged to minimize any pressure sensing variations. This embodiment of the present invention provides for monitoring the distal outlet and proximal inlet pressures of the pump cassette, determining the differential pressure between the two, and adjusts the pumping cycle to compensate for this differential pressure. The pumping cycle is adjusted by increasing or decreasing the pressure of the medicinal fluid within the pump cassette, and if required, changing the timing of the pump cycle.
Prior to the initiation of each pump cycle, the differential pressure is again determined. A correction factor is determined by the algorithm, and the pressure of the medicinal fluid within the pump cassette is adjusted accordingly. As the fluid leaves the pump cassette, its pressure is also used to determine the actual volume of fluid being delivered by the current pump cycle.
This information is used by the algorithm to determine how the timing of the next pump cycle should be varied to achieve a desired flow rate. Preferably, the timing is changed by varying the duration of the delivery stroke of the pump.
This pressure compensation process is repeated for each cycle. Further details of the preferred embodiment are as follows. With reference to FIG. A source 12 of medicinal fluid A and a source 14 of medicinal fluid B are both coupled in fluid communication with a proximal end 16 of a cassette The flow of medicinal fluid A into the cassette is selectively controlled by a supply valve 20 , and the flow of medicinal fluid B is selectively controlled by a supply valve If cassette 15 is to be used to pump only one of these two medicinal fluid at a time, only the appropriate supply valve 18 or 20 is opened to select the medicinal fluid to be pumped.
The selected medicinal fluid or fluids then flow s through an air sensor 22 and into a mixing chamber The EFM demodulator also decodes part of the CD signal and routes it to the proper circuits, separating audio, parity and control subcode data.
After demodulating, a CIRC error corrector takes each audio data frame, stores it in a SRAM memory and verifies that it has been read correctly, if it is not, it takes the parity and correction bits and fixes the data, then it moves it out to a DAC to be converted to an analog audio signal. If the data missing is enough to make recovery impossible, the correction is made by interpolating the data from subsequent frames so the missing part is not noticed.
Each player has a different interpolation ability. If too many data frames are missing or unrecoverable, the audio signal may be impossible to fix by interpolation, so an audio mute flag is raised to mute the DAC to avoid invalid data to be played back. The Redbook standard dictates that, if there is invalid, erroneous or missing audio data, it cannot be output to the speakers as digital noise, it has to be muted.
The Audio CD format requires every player to have enough processing power to decode the CD data; this is normally made by application-specific integrated circuits ASICs. ASICs do not work by themselves, however; they require a main microcomputer or microcontroller to orchestrate the entire machine. As it was easy to manufacture and to use, most CD player manufacturers stayed with the tray style ever since. However, there have been some notable exceptions to this common CD tray design.
During the launch of the first prototype "Goronta" CD player  by Sony at the Japanese Audio Fair in , Sony showcased the vertical loading design. For the early vertical loading players, Alpine sourced their AD player designs for Luxman,  Kenwood and Toshiba using their Aurex brand.
Kenwood added their "Sigma Drive" outputs to this design as a modification. A picture of this early design can be seen on the Panasonic Web site. The holder is closed manually by hand, by motor after pressing a button, or completely automatically.
Some CD players combine vertical loading with slot loading due to the disc being drawn further into the disc holder as it closes. The design had a clamp on the lid which meant the user had to close this over the CD when it was placed inside the machine.
Top-loading was adopted on various equipment designs such as mini systems and portable CD players, but among stereo component CD players, only a handful of top-loading models have been made. They more closely mimic the physical arrangement and ergonomics of record turntables used in those applications. The Philips CD of was the first player to adopt tray loading with a sliding play mechanism.
Basically as the tray came out to collect the CD, the entire player's transport system also came out as one unit. The Meridians and players were of this type. They were also the first to use a design in which the audio electronics were in a separate enclosure from the CD drive and pickup mechanism. A similar mechanism is used in slim optical disc drives also known as slim internal DVD drive, optical drive or DVD burner , which were once commonly used in laptop computers.
Slot loading is the preferred loading mechanism for car audio players. There is no tray that pops out, and a motor is used to assist disc insertion and removal. Some slot-loading mechanisms and changers can load and play back Mini-CDs without the need of an adapter but they may work with limited functionality A disc changer will refuse to operate the changer until the Mini CD is removed for example.
Non-circular CDs cannot be used on such loaders because they cannot handle non-circular discs. When inserted, such discs may become stuck and damage the mechanism. The swing-arm mechanism has a distinctive advantage over the other in that it does not "skip" when the rail becomes dirty. The swing arm mechanisms tend to have a much longer life than their radial counterparts.
The swing-arm mechanism uses a magnetic coil wound over a permanent magnet to provide the tracking movement to the laser assembly in a similar way a hard drive moves its head across the data tracks. It also uses another magnetic movement mechanism attached to the focusing lens to focus the laser beam on the disc surface.
By operating the tracking or the focus actuators, the laser beam can be positioned on any part of the disc. This mechanism employs a single laser beam and a set of four photodiodes to read, focus and keep track of the data coming from the disc.
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Wikimedia Commons. You may review Classicus Electronicus on Bandcamp. You may review Different States of Mine on Bandcamp. The final organization of the album was completed in It will be replaced by a larger collection of my earlier work that includes the tracks from this album.
LP published in by Deep Distance, England. Service Manual. Nakamichi Corporation. Burstein, Herman Audio USA September : 40—43, 45— Hoff, Philip Consumer Electronics for Engineers. Wiley Series in Practical Strategy. Cambridge University Press. Jones, Doug; Manquen, Dale Magnetic Recording and Playback". Handbook for Sound Engineers, Fourth Edition. Kimizuka, Masanori National Museum of Nature and Science. Survey Reports on the Systemization of Technologies. Mallinson, John C.
The Foundations of Magnetic Recording. Roberson, Howard Audio USA September : 44— Rumsey, Francis; McCormick, Tim Sound and Recording: An Introduction. Taylor and Francis. Stark, Craig a. Watkinson, John The Art of Sound Reproduction. Both solenoids and are preferably powered using constant current sources to minimize force variations due to changes in temperature due to power dissipation during operation.
In the preferred system, control solenoid is powered to provide a maximum fluid pressure of about mmHg, while relief solenoid is powered to provide a maximum fluid pressure of about mmHg. As a result, if fluid pressure within tubing segment 36a exceeds about mmHg, control pad and anvil are forced away from segment 36a, increasing fluid flow and decreasing pressure at the irrigation site Relief pad is forced back towards relief solenoid only if pressure in tubing segment 36a exceeds about mmHg.
As a result, relief pad operates as a backup to the pressure relief functions of control pad It will be understood that the forces provide to the solenoids and could be varied as desired.
In addition, the relative force levels provided by the solenoids and could be reversed, i. In operation, the control pad is moved into position a in close proximity with the exposed portion 36a of outflow line 36 whenever the lever is depressed and the race moves towards the pump head Both solenoids and are powered on when lever reaches its final position locking cassette 40 in place.
Mechanism , also moved by the lever , moves the plunger of control solenoid towards or away from the segment 36a and, thereby, also moves the control pad between its rearward, or retracted, position and its forward position indicated at a.
In the forward position, the control solenoid can act with precision over the best portion of its operating range to compress segment 36a against relief pad , thereby regulating fluid flow and pressure at the irrigation site In the rearward position, control pad is retracted from segment 36a so that the cassette 40 can be removed easily.
It will be understood that although the valve assembly described above is particularly advantageous in irrigation systems according to the present invention, it may also be used in any application in which fluid flow is to be restricted using a pinch-type valve operating on a fluid line.
Outflow Tubing Segment. Referring now to FIGS. The preferred tubing segment 36a is flattened to enhance control over pressure in the outflow line 36 and, as a result, also at the irrigation site Although the preferred segment 36a takes the profile described below, it will be understood, however, that segment 36a of the outflow tubing line 36 can take many forms including a standard circular cross-sectional shape.
The profile of the preferred segment 36a has interior corners , preferably with a radius of less than 0. The wall thickness of the tubing should be thin, preferably between about 0.
The wall should be soft, with a durometer of between about 40 to 50 Shore A. An extruded or molded silicone material is preferred, but other low durometer thermoplastics such as polyvinyl chloride may be used. The preferred profile provides advantages by lowering the occlusion force, i.
The profile also reduces the tendency of the tubing to form a "dog bone" shaped profile when the tubing is occluded. The preferred segment 36a may include at least one projection formed in the interior wall surface of the tubing 36a. One preferred projection is seen in greater detail as enlarged in FIG. The projection is provided to prevent the total occlusion of the tubing in the event suction in the outflow line 36 attempts to completely flatten the tube 36a.
A radius of between about 0. The preferred projections extend generally parallel to the axis of the tubing segment 36a see FIG. Although one projection provides some of the benefits described above, it is more preferred to provide at least two projections on opposing sides of the tubing segment 36a.
The preferred projections are also offset from each other along the longer transverse axis of the tubing segment 36a, i. The preferred offset between projections is approximately 0. Referring to the partial view in partial cross-section of FIG. Each fitting includes a pair of nipples which are inserted into the tubing 36 or 36a. Fittings preferably include slots which cooperate with notches 92 in cassette 40 see FIG. In the preferred embodiment, segment 36a is held straight within cassette 40 as best seen in FIG.
Both tubing segment 36a and standard round tubing 36 are connected to fittings using any suitable method including clamps, adhesives, etc. It will be understood that although the flattened tubing segment described above is particularly advantageous in tubing sets and irrigation systems according to the present invention, it may also be used in any application in which fluid flow is to be restricted using a pinch-type valve operating on a fluid line.
Pressure Sensing Line Coupling. As discussed above, fitting 66 connects pressure-sensing line 38 to the fluid control module 24 and port completes the line of connection. The pressure-sensing line 38 preferably terminates in an adapter located loosely within a hole in interior wall 88 of cassette A preferred fitting 66 is attached to one end of the adapter , and located within hole 96 in side wall Hole 96 is preferably oversized to allow fitting 66 to move both axially as well as radially within hole A spring is preferably located between a washer surrounding hole and a flange on the periphery of fitting Spring resiliently biases the fitting 66 towards wall 94 and allows the fitting 66 to "float" within hole 96 in wall 94 of cassette The portion of the side wall 94 immediately adjacent the hole 96 acts as a stop against the flange to limit the axial movement of the fitting 66 under the urging of spring When the cassette 40 is inserted into the cassette-receiving passageway 98 in fluid control module 24, the fitting 66 contacts port A seal , located within a substantially planar region in fitting 66, is pressed against the outer face of port because of the biasing of fitting 66 towards wall 94 by spring in the preferred embodiment.
As a result, fitting 66 and port form a face seal to seal the pressure sensing line 38 with the pressure sensing monitor in the fluid control module Seal can be an O-ring or gasket. A length of tubing , conveniently fitted over a barb , conveys pressure information from pressure sensing line 38 to a pressure transducer in fluid control module 24 so that the valve assembly and motor can be properly controlled to provide the desired pressure in the outflow line 36 and, therefore, at the irrigation site In the preferred coupling, seal is located at the bottom of an opening which widens to form a frustrum of a cone as indicated at surface as shown in FIG.
That construction aids in guiding fitting 66 over port so that the outer face of port is in proper alignment with seal Alternately, it will be understood that shapes of fitting 66 and port could be switched and still provide the desired guiding function. Pressure Control Scheme. As described above, the pump head and race operate on inflow tubing segment 34a to pump fluid towards the irrigation site at a desired flow rate.
Flow rate through and fluid pressure at the irrigation site 22 are both at least partially controlled by the speed of pump head Pressure at the irrigation site and flow rate are also partially controlled by the action of control pad and, more specifically, anvil , which compresses against relief pad to restrict flow through the tubing segment 36a.
By restricting or allowing outflow from the irrigation site 22, pressure at the irrigation site 22 can be increased or decreased. Likewise, pressure at the irrigation site 22 can also be increased or decreased by changing the speed of the motor driving pump head The pressure sensing line 38 and corresponding monitoring equipment within fluid control module 24 provide feedback to the system which is used to control the movement of control pad as well as the speed of the pump head Pressure relief functions are accomplished using the maximum forces provided by the control and relief solenoids and as described in detail above.
These functions will typically activate only if the pressure monitoring and control system operating on the pump speed and control pad movement malfunctions.-CASSETTE GENÉTICO DE RESISTENCIA. White y col. J Bacteriol ; S CHMIDT F, K LOPFER-K AUL I. Evolutionary relation-ship between Tn like elements and pBP, a.