Spinal Cord Stimulation for Respiratory Muscle Activation
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Solution Overview
Problem
Current inspiratory muscle pacing techniques for ventilator-dependent tetraplegics are limited in achieving full-time ventilatory support due to insufficient inspired volume generation and co-activation of non-respiratory muscles, with only about 50% of patients achieving full-time support and many requiring mechanical ventilation.
Innovation Solution
High frequency electrical stimulation of the spinal cord tracts at the upper thoracic level to activate diaphragm, intercostal, and accessory muscles, which mimics physiological breathing patterns and reduces non-respiratory muscle contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional phrenic nerve pacing is used to activate diaphragm, then ventilatory support is provided, but inspired volume is insufficient and non-respiratory muscles are co-activated
Solution Approach 1:
The patent uses the spinal cord as an intermediary structure to deliver stimulation. By placing electrodes on the spinal cord surface, the stimulation is transmitted through spinal pathways to activate respiratory motorneuron pools, which then selectively activate respiratory muscles without co-activating non-respiratory muscles. This intermediary approach solves the problem of non-selective muscle activation in conventional PNP.
Solution Approach 2:
The patent applies stimulation at a specific location (spinal cord surface) with specific characteristics (high frequency, brief duration) to achieve selective activation of respiratory muscles. The local application of high-frequency stimulation to the spinal cord creates a focused effect that activates only respiratory motorneuron pools while leaving non-respiratory motorneuron pools unaffected.
2Reliability
If phrenic nerve pacing is applied at low frequency, then diaphragm activation is achieved, but muscle fiber damage occurs
Solution Approach 1:
The patent fundamentally changes the stimulation parameters from low frequency (conventional PNP) to high frequency (brief duration). This parameter change achieves two things: (1) it maintains effective diaphragm activation through high-frequency spinal cord stimulation, and (2) it prevents muscle fiber damage by using brief stimulation duration. The high-frequency, brief-duration paradigm eliminates the harmful effects of low-frequency stimulation while maintaining therapeutic efficacy.
3Reliability
If mechanical ventilation is used to maintain ventilatory requirements, then basic physiologic needs are met, but multiple handicaps and complications occur
Solution Approach 1:
The patent enables the patient's own respiratory muscles to perform the ventilatory function that would otherwise require mechanical ventilation. By activating the patient's diaphragm, intercostal, and accessory muscles through spinal cord stimulation, the system allows the respiratory system to serve itself, eliminating the need for external mechanical ventilators and their associated complications such as tracheostomy, respiratory tract infections, and mobility restrictions.
4Quantity of substance
If high frequency spinal cord stimulation is applied, then inspired volume increases to 80% of inspiratory capacity, but stimulation complexity increases
Solution Approach 1:
The spinal cord serves as a natural intermediary that simplifies the stimulation system. By stimulating the spinal cord rather than individual nerves or muscles, the system achieves complex respiratory muscle activation (diaphragm, intercostal, and accessory muscles) through a single stimulation site. This intermediary approach reduces device complexity compared to multi-site or multi-nerve stimulation systems while achieving high inspired volume.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method achieves inspired volumes up to 80% of inspiratory capacity, allowing for prolonged ventilatory support without fatigue, and reduces unwanted muscle contractions, enabling ventilator-free time for extended periods.
Implementation Method 1
A stimulus delivered to the spinal cord may result in the generation of action potentials by the stimulated spinal cord
Implementation Method 2
processing of the stimulus within the motorneuron pools resulting in a more physiological pattern of activation
Data Source
AI summary
A method of electrically stimulating the inspiratory muscles in a subject is provided. The method includes positioning one or more electrodes at one or more levels of the upper thoracic spinal cord of the subject and operating the electrode to deliver high frequency electrical stimulation to the spinal cord tracts at the level or levels. The high frequency electrical stimulation of the spinal cord results in the coordinated activation of the diaphragm, intercostal muscles, and accessory muscles in the subject to effect artificial ventilation in the subject.