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

T Technology (General)

McCaughey, Euan James ; Gollee, Henrik

University:University of Glasgow

Department:School of Engineering

关键词: Spinal cord injury, tetraplegia, electrical stimulation, abdominal functional electrical stimulation, ventilator weaning;   

Others  :  http://theses.gla.ac.uk/5471/1/2014mccaugheyphd.pdf

来源: University of Glasgow

【 摘 要 】

An injury to the cervical region of the spinal cord can cause paralysis affecting all fourlimbs, termed tetraplegia. People with tetraplegia also have paralysis or impaired functionof the major respiratory muscles, namely the diaphragm and intercostal and abdominalmuscles. This often reduces respiratory function, with associated respiratory complications aleading cause of morbidity and mortality for this population. Abdominal Functional ElectricalStimulation (AFES), the application of electrical pulses to the abdominal muscles causingthem to contract, has been shown to improve respiratory function in tetraplegia. Despite thesepositive 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 achievedby addressing two primary objectives. Firstly, the development of new technologies andprotocols to optimise AFES for use in a clinical setting. Secondly, the clinical evaluation ofthese technologies and protocols with tetraplegic patients.For research purposes, AFES has typically been applied manually, requiring an operatorto synchronise stimulation with respiratory activity. One important step necessary for theclinical introduction of AFES is the development of an automated AFES device that canapply stimulation in synchrony with the users respiratory activity, with different stimulationparameters applied for different breath types such as a quiet breath and a cough. In thisthesis, the signal from a non-intrusive respiratory effort belt, worn around the chest, wasused to develop a statistical classifcation algorithm capable of classifying respiratory activityin real-time, and applying AFES in synchrony with the user's respiratory activity. Theeffectiveness of AFES can also be enhanced by stimulating at the abdominal muscle motorpoints. In this thesis the positions of the abdominal motor points were located systematicallyfor 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 whowould 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 toimprove the respiratory function of the acute ventilator dependant and sub-acute tetraplegicpopulations was demonstrated. In the first study, conducted with 10 acute ventilatordependant tetraplegics, AFES was applied on alternate weeks for a total duration of eightweeks. 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 frommechanical ventilation on average 11 days faster than matched historic controls.Previous work, which investigated the effect of a three week AFES training programme onthe respiratory function of people with sub-acute tetraplegia, suggested that an extendedAFES 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 ledto an acute increase in respiratory function, with a longitudinal improvement in respiratoryfunction observed throughout the study. In a single participant case study, the feasibilityof combining AFES with assisted coughing delivered by mechanical insufflation-exsufflationwas demonstrated for the first time. This was shown to lead to an acute improvement inrespiratory function at six of the eight assessment sessions, indicating that this techniquecould be used to aid secretion removal.This thesis highlights the feasibility and effectiveness of AFES to improve the respiratoryfunction of the acute ventilator dependant and sub-acute tetraplegic populations. The clinicalprotocols that enable AFES to be used with these patient groups, and the technologicaldevelopments detailed throughout this thesis, are an important step towards the introductionof AFES as a regular treatment modality.