Methods and devices to decrease tissue trauma during surgery

Abstract

Methods and devices are disclosed to reduce tissue trauma when a physician retracts a patient's tissues for surgery. In one part, methods and devices are disclosed for controlling retraction force and pace. In another part, methods and devices are disclosed for oscillating force when opening. In another part, methods and devices are disclosed for detecting trauma during retraction. In another part, methods and devices are disclosed for balancing forces on multiple retraction elements. In another part, methods and devices are disclosed for reducing forces in multiple dimensions. In another part, methods and devices are disclosed for engaging ribs. In another part, methods and devices are disclosed to compensate for deformation of a retractor under load. In another part, methods and devices are disclosed that combine these methods and devices. In another part, methods and devices are disclosed for controlling pressure inside inflatable devices used for deforming biological tissues.

What is claimed is: 
     
         1 . A fluidic system for deforming a biological tissue, comprising:
 an inflatable device comprising a wall configured to be pressed against biological tissue to apply a pressure through the wall to the biological tissue;   a tube attached to the inflatable device, the inflatable device attached at a distal end of the tube and in fluid communication with the tube;   a pump in fluid communication with a proximal end of the tube configured to inflate the inflatable device; and   a compliance flow control device, comprising:
 a pressure release device configured to decrease fluid pressure at the proximal end of the tube; and 
 a controller communicatively coupled to the pressure relief device and configured to receive signals from measuring devices associated with the biological tissue, determine if fluid pressure at the proximal end of the tube should be decreased based on the received signals, and in response cause the pressure relief device to decrease fluid pressure at the proximal end of the tube. 
   
     
     
         2 . The device of  claim 1 , wherein the controller is further configured to control the rate of pumping of the pump. 
     
     
         3 . The device of  claim 1 , wherein the pressure-release device is comprised of a valve that is normally closed and, on signal from the controller, releases fluid from the fluidic system through a path of low fluid resistance. 
     
     
         4 . The device of  claim 1 , wherein the pressure release device is configured to be inactivated after a predetermined period of time. 
     
     
         5 . The device of  claim 4 , wherein when the pressure release device is inactivated, the controller is configured to cause the pump to turn on and re-pressurize the fluidic system to the pressure at which the compliance flow control device activated the pressure release device; and the pump resumes inflating the inflatable device. 
     
     
         6 . The device of  claim 5 , wherein the pump is configured to pause after reaching a predetermined pressure to allow stress relaxation of the biological tissue before further inflating the inflatable device. 
     
     
         7 . The device of  claim 1 , wherein the compliance flow control device further composes:
 a first pressure measuring device in fluid communication with the proximal end of the tube   a controller configured to:
 receive a signal from the first pressure measuring device; perform a plurality of measurements based on the pressure signal over time; 
 compare a substantially instantaneous measurement of the pressure signal to a variance in the plurality of measurements over an interval of time preceding the instantaneous measurement; and 
 detect rupture based on the comparison. 
   
     
     
         8 . The device of  claim 7 , wherein the plurality of measurements are comprised of a plurality of first time derivatives of the first signal. 
     
     
         9 . The device of  claim 7 , wherein the plurality of measurements are comprised of a plurality of second time derivatives of the first signal. 
     
     
         10 . The device of  claim 7 , wherein the variance is comprised of a root-mean-square of the plurality of measurements. 
     
     
         11 . The device of  claim 7 , wherein the control system is further configured to determine if the ratio between the variance in the plurality of measurements and the substantially instantaneous measurement exceed a threshold value. 
     
     
         12 . The device of  claim 1 , wherein the compliance flow control device further composes:
 a first flow measuring device located at the outlet of the pump;   a second flow measuring device located at the proximal end of the tube in fluid communication with the inflatable device;   the controller being in communication with the first flow measuring device and the second flow measuring device and adapted to compare the flows measured by the first measuring device and the second flow measuring device; and   flow measured by second flow measuring device being substantially greater than flow measured by the first flow measuring device indicates rupture of either the biological tissue or the wall of the inflatable device.   
     
     
         13 . The device of  claim 1 , wherein the compliance flow control device further composes:
 a differential pressure measuring device in fluid communication with the fluid at two different points inside the fluidic system such that first pressure measuring point is closer to the pump and second pressure measuring point is further from the pump;   a fluid path having fluid resistance separating the first and second points inside the fluidic system; and   wherein the controller is further configured to receive signals from the differential pressure measuring device.   
     
     
         14 . The device of  claim 1 , wherein the compliance flow control device further comprises:
 a first differential pressure measuring device in fluid communication with the fluid at first and second pressure measuring points inside the fluidic system such that first pressure measuring point is closer to the pump and second pressure measuring point is further from the pump;   a first fluid path having high fluid resistance separating the first and second points inside the fluidic system;   a second differential pressure measuring device in fluid communication with the fluid at third and fourth pressure measuring points inside the fluidic system such that the third pressure measuring point is further than the second measuring point from the pump and fourth pressure measuring point is further than the third pressure measuring point from the pump;   a second fluid path having high fluid resistance separating the third and fourth points inside the fluidic system; and   a comparator adapted to determine the nearly instantaneous ratio of the signals from the two differential pressure measuring devices.   wherein the controller is further configured to receive the signal from the comparator.   
     
     
         15 . The device of  claim 14 , wherein the controller is further configured to perform a plurality of measurements based on the ratio of the second differential pressure signal to the first differential pressure signal over time; and compare a substantially instantaneous measurement of the ratio to a variance in the plurality of measurements over an interval of time preceding the instantaneous measurement; and detect rupture based on the comparison. 
     
     
         16 . The device of  claim 15 , wherein the plurality of measurements are comprised of a plurality of first time derivatives of the ratio. 
     
     
         17 . The device of  claim 15 , wherein the plurality of measurements are comprised of second time derivatives of the ratio. 
     
     
         18 . The device of  claim 15 , wherein the variance is comprised of a root-mean-square of the plurality of measurements. 
     
     
         19 . The device of  claim 15 , wherein the control system is further configured to determine if the ratio exceeds a threshold value. 
     
     
         20 . A method of deforming a biological tissue, comprising:
 pump a fluid from a proximal end of a tube to a distal end of a tube, the distal end of the tube in fluid communication with an inflatable device to inflate a wall of inflatable device against biological tissue to apply a pressure through the wall to the biological tissue;   receiving signals at a controller from measuring devices associated with the biological tissue;   determining in the controller if fluid pressure at the proximal end of a tube should be decreased based on the received signals;   if the fluid pressure should be decreased, the controller causing the pressure relief device to decrease fluid pressure at the proximal end of the tube.