An Investigation into the Factors Influencing Aerobic Power among Patients with Ankylosing Spondylitis with Special Reference to Respiratory Muscle Performance and Perceived Exertional Dyspnoea

[摘要] This thesis embraces a series of related studies spanning fourteen months. An initial questionnaire-based survey identified the presence of undue breathlessness perceived in a significant proportion of patients with ankylosing spondylitis (AS). The finding was substantiated by an oxygen-cost diagram study comprising matched healthy controls. Measurements of respiratory muscle strength and endurance were made in a subsequent study. Although maximal strength of the respiratory muscles was preserved in the AS patients, their respiratory muscle endurance during work requiring high inspiratory pressures was clearly impaired. Upright symptom-limited exercise confirmed that exercise tolerance and aerobic power were commonly curtailed among the AS patients. Relative to matched controls, ventilatory response and heart rate response to exercise in the AS patients were raised. However, the elevated ventilatory and heart rate responses were not accompanied by abnormalities in pulmonary gas exchange, breathing reserve, or other cardiocirculatory indices. Although the AS subjects perceived a higher degree of breathing effort for an equivalent level of work rate or ventilation, they were not ventilatory limited. By contrast, the finding of a greater magnitude of leg fatigue perceived among the AS subjects despite achieving a lower work rate strongly suggested a significant element of peripheral musculoskeletal deconditioning. The elevated heart rate response was compatible with an element of cardiac deconditioning secondary to a relative lack of physical activity. Finally, the relative contribution of pulmonary factors, chest restriction, and muscular function to the reduction in aerobic power among the AS patients was quantitively examined. Peripheral muscle strength was found to exert the strongest influence on aerobic power in the AS patients. The addition of lean body mass further improved the variability explained by the regression model derived. No significant influence of impaired respiratory muscle endurance on aerobic power was observed. Vital capacity and limited chest expansion exerted only weak influences on aerobic power in the AS subjects. The results from the studies comprising this thesis thus emphasise the importance of physical activity in this condition. Suggestions for further interventions/strategies of clinical value were made.

[发布机构] University:University of Glasgow

[关键词] Medicine, Physiology