Method and Apparatus for Saving Energy in an Implantable Stimulator
Publication Date: 2003-Dec-11
The IP.com Prior Art Database
John D. H. King: INVENTOR [+2]
A neurostimulator conserves energy while delivering adequate comfort and therapy to a patient by randomly removing electric stimulation pulses from sequences of removable pulses that are separated by permanent pulses.
Background & Summary
Neurostimulation uses high frequencies of electric pulses for sensory
stimulation. Patients tend to feel more
comfortable when stimulated at higher frequencies. These high frequencies can lead to rapid use of the scarce
available energy in the neurostimulator.
Often, this rapid use of energy necessitates explantation of an
implanted device simply to replace a battery.
Or, in the case of rechargeable systems, a rapid use of energy can
necessitate recharging intervals that are more frequent than is desirable. In order to extend battery life, lower
frequencies can be used, but these lower frequencies often cause discomfort and
decreased therapeutic benefit to a patient.
Therefore, a need exists for a method that permits a stimulation
frequency most preferred by a patient while saving power and therefore
extending battery life or permitting less frequent recharging.
The present method and apparatus addresses the above and other needs by randomly removing electrical pulses from an electrical stimulation pulse train sent from a neurostimulator to a patient’s tissue. In one embodiment, the present method employs an algorithm that randomly removes pulses in order to avoid a pattern of removal that may create an uncomfortable or otherwise recognizable sensation for the patient. In order to avoid the possibility of large numbers of subsequent pulses being removed, the pulse train is divided into protected and unprotected regions. Pulses are only removed from the unprotected regions. The number of individual pulses in each protected region is specified as a first variable in the algorithm. The number of individual pulses in each unprotected region is specified as a second variable in the algorithm. Finally, the percentage of pulses randomly removed from each unprotected region is specified as a third variable in the algorithm. Pulses are randomly removed using a random number generator.
For way of example, a recurring pulse train may consist of five protected pulses followed by five unprotected pulses with a 20% removal rate. This would result in a recurring pulse train of five pulses followed by four out of the next five scheduled pulses. A random number generator determines which one of the five unprotected pulses is removed. This method of random removal thus employs an algorithm that conserves energy in a neurostimulator by decreasing its average pulse rate while providing adequate comfort and therapy to a patient.
Description of Invention
A representative implantable neural stimulator is described, e.g., in International Publication No. WO 02/09808 A1, incorporated herein by reference. In particular, FIGS. 4A, 4B and 4C of the referenced International Publication depict an implantable pulse generator that may be used to practice the present method and apparatus in the context of providing spinal cord stimulation. It is to be understood, however, that other ty...