Model-Based Optimization of Spinal Cord Stimulation for Inspiratory Muscle Activation

Neuromodulation, 2022 · DOI: 10.1111/ner.13415 · Published: December 1, 2022

Simple Explanation

High-frequency spinal cord stimulation (HF-SCS) is being explored as a way to help people with spinal cord injuries who need ventilators to breathe. The study uses computer models to figure out the best way to use electrical stimulation to activate the muscles that help with breathing. The models test different electrode designs to see which ones are best at activating the nerves and muscles needed for breathing. The goal is to find the ideal setup for stimulating these muscles effectively. The modeling and experimental results support the potential advantages of a lead design with longer contacts and larger edge-to-edge contact spacing to maximize inspiratory muscle activation during HF-SCS at the T2 spinal level.

Study Duration

Not specified

Participants

Three adult mongrel male dogs

Evidence Level

Not specified

Key Findings

1
Model results suggested that within physiological stimulation amplitudes, HF-SCS activates both axons in the ventrolateral funiculi (VLF) and inspiratory intercostal motoneurons.
2
A lead design with longer contacts (6 mm) and large rostrocaudal contact spacing (12 mm) would lead to optimal recruitment of both VLF fibers and motoneurons.
3
In vivo results were in excellent agreement with computational model predictions, supporting the potential advantages of a lead design with longer contacts and larger edge-to-edge contact spacing.

Research Summary

This study used computational models and experimental testing to investigate HF-SCS recruitment of axons in the VLF and motoneurons innervating the inspiratory intercostal muscles. The study evaluated HF-SCS recruitment with various lead designs and stimulation configurations, and tested two of these lead designs via in vivo canine experiments. The results suggest that maximal inspiratory activity is produced with monopolar, bipolar, or tripolar stimulation configurations applied with wire electrode leads with longer contacts (e.g., 6 mm length) and larger edge-to-edge contact spacing (e.g., 12 mm).

Practical Implications

Improved HF-SCS Technologies

The results of this study will help improve the efficacy of HF-SCS technologies for inspiratory muscle pacing.

Optimal Lead Design

A lead design with longer contacts and larger edge-to-edge contact spacing may improve inspiratory activity generated during ventral HF-SCS.

Mechanisms of Spinal Cord Stimulation

The findings provide insight into the mechanisms of action of ventral HF-SCS to activate the inspiratory muscles and optimize lead design.

Study Limitations

1
Computational model did not consider the downstream effects of HF-SCS on the neural circuits responsible for inspiration.
2
The study did not consider additional neural elements, such as afferent fibers and interneurons making direct synaptic connections onto the intercostal motoneurons.
3
Secondary effects of the stimulation, such as the activation of limb muscles, were not fully explored.

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