Injectable Microstimulators for Minimally Invasive Cough Induction
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Solution Overview
Problem
Current methods for inducing expiratory function in subjects with spinal cord injury (SCI) are invasive, risky, and require active assistance, leading to respiratory complications and infections, as they involve direct implantation of electrodes or external magnetic stimulation with inconvenient equipment.
Innovation Solution
The use of minimally-invasive injectable microstimulators placed adjacent to thoracic spinal nerves to induce forced expiration, which can be remotely activated without lead lines, allowing for efficient implantation and reducing infection risks, and can be used to generate effective coughs similar to more invasive technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct implantation of epidural FES electrodes is used, then expiratory function can be produced, but surgical trauma and infection risk increase
Solution Approach 1:
The invention extracts the stimulation function from the epidural space and relocates it to the paraspinal soft tissue. By placing electrodes in the paraspinal region rather than directly on the epidural space, the patent eliminates the need for major spinal surgery while maintaining expiratory muscle stimulation capability. This extraction of the stimulation function from the dangerous epidural location resolves the contradiction between reliable expiratory function production and avoidance of surgical trauma.
Solution Approach 2:
The paraspinal soft tissue acts as an intermediary medium between the external electrode and the target spinal nerves. Instead of directly stimulating the epidural space (which causes trauma), the patent uses paraspinal electrodes as an intermediary to indirectly stimulate the spinal nerves, thereby achieving expiratory function while avoiding direct surgical trauma to the spinal cord.
2Reliability
If external magnetic stimulation is used, then expiratory function can be produced, but device convenience and usability deteriorate
Solution Approach 1:
The patent replaces the external magnetic field mechanism with a direct electrical stimulation mechanism. Instead of using cumbersome external magnets and magnetic coils that require precise positioning and complex equipment, the invention uses implanted electrical electrodes that deliver stimulation directly to the spinal nerves. This substitution of mechanical/magnetic systems with electrical systems significantly improves device convenience and usability while maintaining expiratory function production.
Solution Approach 2:
The implanted electrodes provide self-contained stimulation capability without requiring external magnetic equipment. The electrodes are integrated with lead wires that connect to a simple external pulse generator, eliminating the need for complex external magnetic stimulation devices. This self-service approach where the implanted electrodes autonomously perform the stimulation function resolves the contradiction between reliable expiratory function and ease of operation.
3Reliability
If invasive electrode implantation is used, then effective cough generation is achieved, but recovery time increases due to surgical trauma
Solution Approach 1:
The invention extracts the electrode implantation from the spinal cord area and relocates it to the paraspinal soft tissue. This extraction allows for minimal invasive placement through small incisions rather than major spinal surgery, thereby achieving effective cough generation while significantly reducing recovery time. The paraspinal location permits electrode placement without disrupting the spinal cord or requiring extensive surgical exposure.
Solution Approach 2:
The patent changes the anatomical parameter of electrode placement from epidural/spinal cord location to paraspinal soft tissue location. This parameter change fundamentally alters the invasiveness level, transforming a major surgery into a minimal invasive procedure. The new placement parameter allows for quicker healing and shorter recovery time while maintaining the effectiveness of cough generation through proper neural stimulation.
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
The microstimulators effectively produce expiratory functions like coughing with reduced risk of infection and trauma, facilitating quicker recovery and equivalent airway pressure generation compared to invasive methods, making them a viable alternative for SCI patients and others with respiratory impairments.
Implementation Method 1
applying a stimulating electrical current from the microstimulator to the thoracic spinal nerve at a sufficient intensity and duration to induce a forced contraction of the intercostal muscle
Implementation Method 2
FMS is achieved by an external application of electromagnetic energy to the spinal cord. For example, maximal expiratory pressure generated by FMS was 83.6±16.4 cm H2O when a magnetic coil was placed at T9 spinous process
Data Source
AI summary
A method of inducing forced expiration in a subject is disclosed. The method can include percutaneously placing an injectable microstimulator adjacent at least one thoracic spinal nerve that innervates an intercostal muscle. For example, the microstimulator is placed within 8 cm externally of a neuroforamen through which the spinal nerve emerges from a thoracic vertebra. The method can also entail applying a stimulating electrical current from the microstimulator to the thoracic spinal nerve at a sufficient intensity and duration to induce a forced contraction of the intercostal muscle innervated by that spinal nerve.