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Title: Investigations of respiratory muscle function in children with neuromuscular disease using a novel device
Author: Heraghty, Jane Lesley
ISNI:       0000 0004 6056 6479
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2015
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In progressive neuromuscular diseases such as Duchenne muscular dystrophy (DMD), loss of respiratory muscle strength and endurance leads initially to nocturnal hypercapnia and then daytime respiratory failure. Non-invasive ventilation has improved quality of life and survival but requires overnight sleep assessments and there remains uncertainty about the optimal time to initiate non-invasive ventilation. The aim of this project was to develop a method to identify patients at high risk of nocturnal hypoventilation in a clinic-based setting. The main work was modifying and testing measurements made with a novel device, the respiratory muscle analyser (MicroRMA) that was developed to measure respiratory muscle endurance. The MicroRMA allowed incremental loading of the respiratory muscles after a pre determined number of breaths. The device calculated energy as a product of time, pressure and flow. Protocols were developed in healthy adults, then healthy children to produce a brief and tolerable 6-minute test of respiratory muscle endurance. Several protocols were tested and the outputs of the device compared. The main hypothesis was that children at high risk of nocturnal hypoventilation would be more likely to fail to complete a standardised test protocol or would adapt their respiration to use less cumulative energy to accomplish test completion. Children with neuromuscular weakness had a lower completion rate on some protocols but test failure was not associated with other markers of disease severity, including lower forced vital capacity or nocturnal hypercapnia. Similarly, in children completing the test protocol, no relationship between MicroRMA outputs and disease severity was detected. In addition, handgrip strength was also evaluated in DMD but lower strength was not related to worse nocturnal gas exchange. Finally, overnight oximetry was compared with oxicapnography but, using recommended threshold criteria, only identified half of the children with nocturnal hypercapnia. In conclusion, none of the tests evaluated were able to predict which children with neuromuscular weakness had nocturnal hypercapnia.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available