Skip to main content
  • Poster presentation
  • Open access
  • Published:

Computational model of human ventilation for electrical stimulation following cervical spinal cord injury

Towards the development of an implantable stimulator for respiratory pacing, we have developed a computational model of the human ventilatory system to simulate breathing maneuvers. Following cervical spinal cord injury, control of breathing is lost or diminished. If the loss is severe, patients are dependent on mechanical ventilators or electrical stimulators to regain functional breathing. Existing electrical stimulation based respiratory pacing systems typically activate only the diaphragm and cannot adapt to muscle fatigue, changes in respiratory demands, or changes in electrode quality over time. This model will be used to test stimulation controllers that can adapt to such conditions. The model was developed in Simulink/SimMechanics implementing the physiologically realistic muscle model from MSMS [1, 2] using published parameters for muscle geometry [3, 4]. Diaphragm geometry was modeled as a pulley system in one dimension. Ventilatory compliance was modeled as a damped spring with non-linear stiffness. Integrated phrenic drive was modeled as either a spaced sawtooth (tidal breathing) or a step function (maximal inspiration). The model was able to reproduce tidal breathing and maximal inspiration for uninjured subjects (see Figure 1). When simulating electrical stimulation without fatigue, maximal inspiration was similar but tidal breathing was higher due to the recruitment of larger motor units first. When simulating electrical stimulation as well as fatigue (50% reduction in maximal force and a decrease in the power of the fast motor units), tidal breathing was similar to the uninjured case (see Figure 1). Thus, even with fatigue, electrically stimulated muscles are strong enough to produce the submaximal contractions needed for tidal breathing. In the future, this model will be enhanced to incorporate additional muscles of respiration as well as atrophy associated with spinal cord injury and will be used to iteratively develop adaptive controllers to achieve functional ventilation and to promote weaning from a mechanical ventilator.

Figure 1
figure 1

Diaphragm displacement during tidal breathing (grey lines) and maximal inspiration (black lines). Uninjured curves (solid lines) reproduce published experimental data. When simulating electrical stimulation (reverse recruitment) and fatigue (a 50% reduction in maximal muscle force), tidal breathing results are similar to uninjured simulations due to increased force generated by the larger motor units being recruited first (dashed lines).

References

  1. Cheng EJ, Brown IE, Loeb GE: Virtual muscle: a computational approach to understanding the effects of muscle properties on motor control. J Neurosci Methods. 2000, 101: 117-130. 10.1016/S0165-0270(00)00258-2.

    Article  CAS  PubMed  Google Scholar 

  2. Song D, Raphael G, Lan N, Loeb GE: Computationally efficient models of neuromuscular recruitment and mechanics. J Neural Eng. 2008, 5: 175-184.

    Article  CAS  PubMed  Google Scholar 

  3. Gorman RB, McKenzie DK, Pride NB, Tolman JF, Gandevia SC: Diaphragm length during tidal breathing in patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med. 2002, 166: 1461-1469. 10.1164/rccm.200111-087OC.

    Article  PubMed  Google Scholar 

  4. Stubbings AK, Moore AJ, Dusmet M, Goldstraw P, West TG, Polkey MI, Ferenczi MA: Physiological properties of human diaphragm muscle fibres and the effect of chronic obstructive pulmonary disease. J Physiol. 2008, 586: 2637-2650. 10.1113/jphysiol.2007.149799.

    Article  PubMed Central  CAS  PubMed  Google Scholar 

Download references

Acknowledgements

This work was supported by NIH R01-NS086088.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Brian K Hillen.

Rights and permissions

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Hillen, B.K., Jung, R. Computational model of human ventilation for electrical stimulation following cervical spinal cord injury. BMC Neurosci 15 (Suppl 1), P133 (2014). https://doi.org/10.1186/1471-2202-15-S1-P133

Download citation

  • Published:

  • DOI: https://doi.org/10.1186/1471-2202-15-S1-P133

Keywords