Low energy implantable devices and methods of use

Abstract

Systems, devices, and methods for delivering one or more electrical pulses to a target region within a patient's body are disclosed herein. An implantable neurostimulator for delivering such one or more electrical pulses can include a hermetic housing made of a biocompatible material, an energy storage feature, and at least one lead. The implantable neurostimulator can further include stimulation circuitry that can include a first circuit and a second circuit. The first circuit can include an adjustable resistance element having a first terminal and a second terminal, a first switch coupled to the first terminal of the adjustable resistance element and selectively coupleable with a stimulation-voltage node and a ground node, a second switch selectively coupling the a first one of the plurality of electrodes to one of: the second terminal of the adjustable resistance element; and the stimulation-voltage node.

What is claimed is: 
     
         1 . An implantable neurostimulator for delivering one or more electrical pulses to a target region within a patient's body, the implantable neurostimulator comprising:
 a hermetic housing comprising a biocompatible material;   an energy storage feature configured to power the implantable neurostimulator;   at least one lead coupled to the hermetic housing and comprising a plurality of electrodes located proximate to a distal end of the at least one lead; and   stimulation circuitry comprising:
 a first circuit comprising:
 an adjustable resistance element having a first resistance and comprising a first terminal and a second terminal; 
 a first switch coupled to the first terminal of the adjustable resistance element, the first switch selectively coupleable with a stimulation-voltage node and a ground node; 
 a second switch selectively coupling a first one of the plurality of electrodes to one of: the second terminal of the adjustable resistance element; and the stimulation-voltage node; and 
 
 a second circuit selectively coupleable to a second one of the plurality of electrodes. 
   
     
     
         2 . The implantable neurostimulator of  claim 1 , wherein the adjustable resistance element comprises a variable resistor comprising at least one of: a potentiometer; or a rheostat. 
     
     
         3 . The implantable neurostimulator of  claim 1 , wherein the adjustable resistance element comprises at least one of: a digital resistor; or a bank of resistors switchably connectable to generate a desired combined resistance. 
     
     
         4 . The implantable neurostimulator of  claim 1 , further comprising a processor configured to control the first and second switches to generate a stimulation pulse. 
     
     
         5 . The implantable neurostimulator of  claim 4 , wherein the second circuit comprises: a second adjustable resistance element having a second resistance and comprising a first terminal and a second terminal; a third switch coupled to the first terminal of the second adjustable resistance element, the third switch selectively coupleable with the stimulation-voltage node and the ground node; and a fourth switch selectively coupling the second one of the plurality of electrodes to one of: the second terminal of the second adjustable resistance element; and the stimulation-voltage node. 
     
     
         6 . The implantable neurostimulator of  claim 5 , wherein the processor is further configured to control the third and fourth switches in connection with the control of the first and second switches to generate the stimulation pulse. 
     
     
         7 . The implantable neurostimulator of  claim 6 , further comprising a first capacitor located between the second switch and the first one of the plurality of electrodes and a second capacitor located between the fourth switch and the second one of the plurality of electrodes. 
     
     
         8 . The implantable neurostimulator of  claim 7 , wherein the processor is configured to control the first, second, third, and fourth switches to selectively charge and discharge at least one of the first and second capacitors. 
     
     
         9 . The implantable neurostimulator of  claim 8 , wherein the processor is configured to adjust the resistance of at least one of the adjustable resistance element and the second adjustable resistance element to control a rate of at least one of the charging and the discharging of the at least one of the first and second capacitors. 
     
     
         10 . The implantable neurostimulator of  claim 9 , wherein the processor is further configured to repeatedly determine an impedance of tissue in the target region of the patient's body. 
     
     
         11 . The implantable neurostimulator of  claim 10 , wherein the processor is configured to repeatedly determine the impedance of tissue in the target region of the patient's body based on a current through the adjustable resistance element and a voltage of the stimulation-voltage node. 
     
     
         12 . The implantable neurostimulator of  claim 10 , wherein the processor is further configured to control the stimulation circuitry to deliver a stimulation pulse having a desired amplitude. 
     
     
         13 . The implantable neurostimulator of  claim 12 , wherein controlling the stimulation circuitry to deliver a stimulation pulse having a desired amplitude comprises controlling the stimulation circuitry to deliver a plurality of stimulation pulses with progressively increasing amplitudes until the stimulation pulse having the desired amplitude is delivered. 
     
     
         14 . A method of delivering stimulation to a target tissue of a patient, the method comprising:
 coupling a first electrode of a lead comprising a plurality of electrodes to a first circuit of a stimulation circuitry an implantable pulse generator;   coupling a second electrode of the lead to a second circuit of the stimulation circuitry of the implantable pulse generator;   delivering a first phase of a stimulation pulse via implementing of a first switch configuration in the first circuit and in the second circuit of the stimulation circuitry, wherein the first circuit comprises:
 an adjustable resistance element comprising a first terminal and a second terminal; 
 a first switch coupled to the first terminal of the adjustable resistance element, the first switch selectively coupleable with a stimulation-voltage node and a ground node; 
 a second switch selectively coupling the a first one of the plurality of electrodes to one of: the second terminal of the adjustable resistance element; and the stimulation-voltage node; 
 wherein the first switch configuration couples the first switch of the first circuit to a ground node and the second circuit to a stimulation voltage node, 
   implementing a second switch configuration corresponding to an interphase delay in the first circuit and in the second circuit;   delivering a second phase of the stimulation pulse via implementing of a third switch configuration, wherein the third switch configuration couples both the first circuit and the second circuit to a node; and   adjusting a resistance of the adjustable resistance element in the first circuit to control a current of the second phase of the stimulation pulse.   
     
     
         15 . The method of  claim 14 , further comprising measuring an impedance of the target tissue prior to delivering the second phase of the stimulation pulse. 
     
     
         16 . The method of  claim 15 , wherein the adjustable resistance element is adjusted according to the measured impedance of the target tissue. 
     
     
         17 . The method of  claim 16 , further comprising controlling a current of the first phase of the stimulation pulse via at least one of: controlling a voltage of the stimulation voltage node; or adjusting the resistance of the adjustable resistance element. 
     
     
         18 . The method of  claim 17 , wherein a second direction of the current of the stimulation pulse in the second phase is in a direction opposite to a first direction of the current of the stimulation pulse in the first phase. 
     
     
         19 . The method of  claim 17 , wherein the adjustable resistance element comprises a plurality of resistors switchably connectable to generate a desired combined resistance, and wherein adjusting the resistance of the adjustable resistance element comprises changing a switch configuration of at least one of the plurality of resistors. 
     
     
         20 . The method of  claim 19 , wherein the node comprises a common voltage node. 
     
     
         21 . The method of  claim 19 , wherein the node comprises the stimulation voltage node. 
     
     
         22 . The method of  claim 21 , wherein the voltage of the stimulation voltage node is set to a first voltage during the first phase and to a second voltage during the second phase. 
     
     
         23 . The method of  claim 14 , wherein the second switch configuration comprises opening of at least one switch of the stimulation circuitry. 
     
     
         24 . The method of  claim 14 , wherein a charge of the first phase of the stimulation pulse is equal to a charge of the second phase of the stimulation pulse. 
     
     
         25 . A method of delivering stimulation to a target tissue of a patient with an implantable pulse generator, the method comprising:
 determining a desired value of a current of desired stimulation pulse;   delivering a first stimulation pulse having a first current, wherein the first current of the first stimulation pulse has a value less than the desired value of the current of the desired stimulation pulse;   measuring a first impedance of the target tissue of the patient at the first current of the first stimulation pulse; and   delivering a second stimulation pulse having a second current set based on the first impedance.   
     
     
         26 . The method of  claim 25 , wherein the second current is equal to the desired value of the current of the desired stimulation pulse. 
     
     
         27 . The method of  claim 25 , wherein the second current is less than the desired value of the current of the desired stimulation pulse. 
     
     
         28 . The method of  claim 27 , further comprising: measuring a second impedance of the target tissue of the patient at the second current; and delivering a third stimulation pulse having a third current set based on the second impedance. 
     
     
         29 . The method of  claim 28 , wherein the third current is greater than the second current, and wherein the second current is greater than the first current. 
     
     
         30 . The method of  claim 28 , wherein each of the first stimulation pulse, the second stimulation pulse, and the third stimulation pulse comprise a first pulse delivery phase having a first phase current and a second pulse delivery phase having a second phase current. 
     
     
         31 . The method of  claim 30 , wherein the first phase current is controlled via at least one of: control of a voltage of a node selectably coupleable to the target tissue of the patient via stimulation circuitry of the implantable pulse generator; or control of a resistance of an adjustable resistance element of the stimulation circuitry. 
     
     
         32 . The method of  claim 31 , wherein the second phase current is controlled via control of the resistance of the adjustable resistance element of the stimulation circuitry. 
     
     
         33 . The method of  claim 29 , wherein the third current is equal to the desired value of the current of the desired stimulation pulse. 
     
     
         34 . A method of delivering stimulation to a target tissue of a patient with an implantable pulse generator, the method comprising:
 determining a desired value of a current of a desired stimulation pulse;   iteratively:
 delivering a test stimulation pulse with stimulation circuitry having a setting to deliver a current less than the desired value of the current of the desired stimulation pulse; 
 measuring an impedance of the target tissue of the patient during delivery of the test stimulation pulse; and 
 until the current of the test stimulation pulse approximately matches the desired value of the current of the desired stimulation pulse, updating the setting of the stimulation circuitry to deliver an increased stimulation current. 
   
     
     
         35 . The method of  claim 34 , wherein each of the stimulation pulses comprises a first pulse delivery phase having a first phase current and a second pulse delivery phase having a second phase current. 
     
     
         36 . The method of  claim 35 , wherein a second direction of the current of the stimulation pulse in the second phase is in a direction opposite to a first direction of the current of the stimulation pulse in the first phase. 
     
     
         37 . The method of  claim 35 , wherein the current of the test stimulation pulse approximately matches the desired value of the current of the desired stimulation pulse when at least one of: the first phase current; or the second phase current approximately matches the desired value of the current of the desired stimulation pulse. 
     
     
         38 . The method of  claim 35 , wherein the at least one of: the first phase current; or the second phase current approximately matches the desired value of the current of the desired stimulation pulse when the current of the at least one of: the first phase current; or the second phase current is within predetermined range about the desired value of the current of the desired stimulation pulse. 
     
     
         39 . The method of  claim 34 , further comprising: repeatedly delivering stimulation pulses with stimulation circuitry having the setting to match the setting of the test stimulation pulse approximately matching the desired value of the current of the desired stimulation pulse; determining a change in the impedance of the target tissue; and adjusting the setting of the stimulation circuitry based on the changed impedance of the target tissue. 
     
     
         40 . The method of  claim 39 , wherein updating the setting of the stimulation circuitry comprises updating a resistance of an adjustable resistance element. 
     
     
         41 . The method of  claim 39 , wherein updating the setting of the stimulation circuitry comprises updating the voltage of a voltage node selectively coupled to the stimulation circuitry.