Abdominal functional electrical stimulation to improve respiratory function in acute and sub-acute tetraplegia

McCaughey, Euan James (2014) Abdominal functional electrical stimulation to improve respiratory function in acute and sub-acute tetraplegia. PhD thesis, University of Glasgow.

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Abstract

An injury to the cervical region of the spinal cord can cause paralysis affecting all four limbs, termed tetraplegia. People with tetraplegia also have paralysis or impaired function of the major respiratory muscles, namely the diaphragm and intercostal and abdominal muscles. This often reduces respiratory function, with associated respiratory complications a leading cause of morbidity and mortality for this population. Abdominal Functional Electrical Stimulation (AFES), the application of electrical pulses to the abdominal muscles causing them to contract, has been shown to improve respiratory function in tetraplegia. Despite these positive results, further work is needed to establish AFES as a standard clinical treatment. The aim of this thesis is to support the clinical introduction of AFES. This was achieved by addressing two primary objectives. Firstly, the development of new technologies and protocols to optimise AFES for use in a clinical setting. Secondly, the clinical evaluation of these technologies and protocols with tetraplegic patients. For research purposes, AFES has typically been applied manually, requiring an operator to synchronise stimulation with respiratory activity. One important step necessary for the clinical introduction of AFES is the development of an automated AFES device that can apply stimulation in synchrony with the users respiratory activity, with different stimulation parameters applied for different breath types such as a quiet breath and a cough. In this thesis, the signal from a non-intrusive respiratory effort belt, worn around the chest, was used to develop a statistical classifcation algorithm capable of classifying respiratory activity in real-time, and applying AFES in synchrony with the user's respiratory activity. The effectiveness of AFES can also be enhanced by stimulating at the abdominal muscle motor points. In this thesis the positions of the abdominal motor points were located systematically for the frst time, in ten able bodied and five tetraplegic participants. To aid the clinical introduction of AFES it is necessary to establish the patient groups who would benefit most from this intervention, and to develop appropriate clinical protocols. This is addressed in two clinical studies, where the feasibility and effectiveness of AFES to improve the respiratory function of the acute ventilator dependant and sub-acute tetraplegic populations was demonstrated. In the first study, conducted with 10 acute ventilator dependant tetraplegics, AFES was applied on alternate weeks for a total duration of eight weeks. This resulted in acute improvements in breathing and led to a longitudinal increase in respiratory function over the study duration. It was found that participants weaned from mechanical ventilation on average 11 days faster than matched historic controls. Previous work, which investigated the effect of a three week AFES training programme on the respiratory function of people with sub-acute tetraplegia, suggested that an extended AFES training programme may be more effective. In the second clinical study in this thesis, a continuous eight week AFES training protocol (combined with a six week control period) was evaluated with three sub-acute tetraplegic participants. The application of AFES led to an acute increase in respiratory function, with a longitudinal improvement in respiratory function observed throughout the study. In a single participant case study, the feasibility of combining AFES with assisted coughing delivered by mechanical insufflation-exsufflation was demonstrated for the first time. This was shown to lead to an acute improvement in respiratory function at six of the eight assessment sessions, indicating that this technique could be used to aid secretion removal. This thesis highlights the feasibility and effectiveness of AFES to improve the respiratory function of the acute ventilator dependant and sub-acute tetraplegic populations. The clinical protocols that enable AFES to be used with these patient groups, and the technological developments detailed throughout this thesis, are an important step towards the introduction of AFES as a regular treatment modality.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Spinal cord injury, tetraplegia, electrical stimulation, abdominal functional electrical stimulation, ventilator weaning
Subjects: T Technology > T Technology (General)
Colleges/Schools: College of Science and Engineering > School of Engineering
Funder's Name: UNSPECIFIED
Supervisor's Name: Gollee, Dr. Henrik
Date of Award: 2014
Depositing User: Mrs Marie Cairney
Unique ID: glathesis:2014-5471
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 04 Sep 2014 08:59
Last Modified: 04 Sep 2014 11:05
URI: http://theses.gla.ac.uk/id/eprint/5471

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