referring in particular to fig1 , an exemplary system 10 constructed in accordance with the principles of the present invention comprises a driver assembly 12 which includes a controller 14 , a syringe 16 , and a motor 18 . typically , the motor will drive a lead screw 20 as shown in fig2 and 3a in order to advance a carriage 22 which is coupled to a plunger 24 of the syringe . the plunger 24 , in turn , may either be advanced in a distal direction ( to the right in fig2 ) in order to deliver inflation medium from a barrel 26 of the syringe or may be retracted in a proximal direction in order to draw new inflation medium into the barrel , as will be described in more detail below . referring now to fig1 , and 5 , a connector 28 at a distal end of the syringe barrel 26 may be removably connected to a y - fitting 32 which has two ports which are connected to a first one - way valve 34 and a second one - way valve 48 , respectively . the first one - way valve 34 , in turn , is removably connected to a connecting tube 38 which connects , at its distal end , to a pressure sensor 36 . pressure sensor 36 , in turn , is connected to cable 30 which provides a pressure signal to the controller 14 within the delivery assembly 12 . the pressure sensor 36 is further removably connected to a catheter 40 which in turn delivers inflation medium to the expandable and inflatable bladder 42 . the first one - way valve 34 is oriented so that it allows flow from the syringe 16 , which is caused by advancement of the plunger 24 , to pass through the fitting 32 , through the fitting 34 , to the tube 38 , through the pressure sensor 36 , and finally through the catheter 40 into the inflatable bladder . the one - way valve 34 will prevent any backflow from the bladder 42 or elsewhere back into the syringe 16 , thus reducing the risk of contamination . the second one - way valve 48 , in contrast , is oriented to cause inflation medium from a refill source 52 connected by a connecting tube 50 to flow back into the syringe barrel 26 when the plunger is retracted in order to draw the medium into the syringe . a needle 54 which is connectable to the tubing 15 is configured to be inserted into the source of saline or other inflation medium 52 so that the syringe maybe refilled between successive activations to deliver the inflation medium to the inflatable bladder 42 . the controller 14 will be programed to allow convenient refilling performed by the user . a cover 56 is provided to maintain sterility of the needle between successive uses . another cover 57 is provided to cover and maintain sterility of the syringe during use . fig3 a and 3b illustrate certain control and other features present on the driver assembly 12 of the systems of the present invention . a battery cover 62 can be removed to replace batteries as shown also in fig2 . a touch screen or other display 70 may be provided on the enclosure of the driver as a user interface . the display 70 will include , either virtually or mechanically , a power switch 72 , a status light 74 , a ready light 76 , an incrementing key 78 , a decrementing key 80 , a run / stop key 82 , and a syringe operation indicator 84 . the syringe maybe removed and replaced on the top of the driver assembly 12 . in particular , the syringe is held in place by a securing strap 92 . the plunger 24 is engaged by a slot 90 in the carriage 22 , as best seen in fig4 b . similarly , the syringe barrel flange 88 is held in another slot 88 , as best seen in fig4 a . the position of the plunger maybe monitored , when the top 57 is in place , with a travel indicator 86 on the display panel 70 . the carriage 22 maybe released from the lead screw 20 by a carriage release button 94 . referring now to fig6 , the inflation control system 10 of the present invention may be used by first connecting the catheter 40 to the pressure sensor 36 which in turn has been coupled to the driver 12 , as described above . after making sure that the syringe 10 has a sufficient volume of inflation medium , the drive 12 may be turned on using switch 82 which will initiate the sequence of operations illustrated in fig6 . initially , the pressure from sensor 36 is checked . if the pressure exceeds the high pressure threshold level p h , the driver will be stopped and an alert or alarm raised since high pressure should not be present at this point in the protocol . assuming that the initial pressure check is successful , the controller 14 will initiate power to the motor 18 in order to rotate the lead screw 20 which advances the carriage 22 which in turn drives the plunger 24 at a relatively low rate , typically the volumetric flow ranges set forth about . the pressure sensor 36 will monitor pressure while the syringe is delivering fluid , and the controller 14 will allow continued delivery for so long as the pressure does not exceed the high threshold value p h , again typically within the ranges set forth above . assuming that no high pressure is detected , the syringe will be driven for a time sufficient to transfer the desired incremental volume v i to the bladder 42 . typically the volume will be from about 1 cc to 10 cc and it will take from 5 seconds to 60 seconds to complete the delivery . if , however , the pressure sensor detects a pressure above the high threshold level p h , the controller will stop the pump and continue to monitor the pressure . for so long as the pressure remains above a low pressure threshold p l , which is typically 5 to 10 mmhg lower than the high pressure threshold p h , the pump will remain stopped . as soon as the pressure falls below this lower pressure threshold p l , the pump will be restarted and the inflation medium will continue to be delivered for so long as the pressure remains below the high pressure threshold p h . pumping will continue until the entire incremental volume v i has been delivered , at which time the pumping is stopped and not restarted until after the passage of a preselected time interval until the scheduled delivery of the successive incremental volumes v i + 1 , i + 2 , . . . , typically in the time ranges set forth above . such successive incremental volume deliveries will continue until the total cumulative volume v t of inflation medium has been delivered to the inflatable bladder . such total volume may take days or even weeks . in some instances , it may be desirable to divide the delivery of the total volume of inflation medium into stages , for example 2 , 3 , 4 , 5 , or even more stages , where the time between successive stages is greater than the normal time between the delivery of the incremental volumes .
a tissue expansion system includes driver assembly having a syringe pump and a controller held in a common enclosure . the driver assembly is connected to both an inflatable bladder and an inflation medium source . fluid is delivered from the driver assembly to the inflatable bladder through a pressure sensor . the pump is actuated to deliver predetermined incremental volumes of the inflation medium to the inflatable bladder at spaced apart time intervals . pressure is monitored and the pumping is interrupted if the pressure exceeds a predetermined high threshold value . pumping is recommenced when the pressure falls below a lower threshold value until the total incremental delivery volume has been reached .