|Institution:||University of Birmingham|
|Keywords:||RC1200 Sports Medicine|
|Full text PDF:||http://etheses.bham.ac.uk/6756/|
Introduction: Sympathetic nerve activity (SNA) undergoes physiological modulation by respiration but it remains unclear whether this process is altered by age and hypertension. Aims: To establish relationship between respiration and neural regulation of the cardiovascular system in aging and hypertension. Methods: Multiunit muscle SNA, BP, respiratory parameters and heart rate were recorded at rest in young and older healthy men and hypertensive patients, then repeated in hypertensive group after acute and long-term device-guided slow deep-breathing (SDB) training. Results: Muscle SNA was higher in older subjects but showed similar modulation by respiration in both age groups. In young acute SDB reduced SNA, with no effect on sympathetic and cardiac baroreflex sensitivity. The sympathoinhibition was not related to changes in baroreflex sensitivity, but it reflected increases in lung inflation afferent input and/or reduction in central respiratory-sympathetic coupling. Long-term SDB training inhibited muscle SNA in hypertensive patients and led to acute increase in heart rate variability and longer-term BP reduction. There were no changes in baroreflex sensitivity, cardiac structure/function or arterial stiffness in response to SDB training. Conclusions: The study provides new mechanistic insights into sympathetic regulatory pathways in hypertension and aging, which may help to establish anti-hypertensive strategy based on respiratory modulation.