Obstructive sleep apnoea and the autonomic nervous system.

Area of Science:

• Cardiology
• Sleep Medicine
• Autonomic Neuroscience

Background:

• Obstructive sleep apnoea (OSA) is a common condition with significant cardiovascular implications.
• Recent research has focused on the autonomic nervous system's role in OSA-related haemodynamic changes.
• Established links exist between OSA, hypertension, and cardiovascular morbidity.

Purpose of the Study:

• To investigate the acute and chronic autonomic nervous system changes in obstructive sleep apnoea.
• To explore the mechanisms underlying these autonomic alterations.
• To assess the impact of Continuous Positive Airway Pressure (CPAP) therapy on autonomic function and cardiovascular changes in OSA patients.

Main Methods:

• Utilized advanced physiological monitoring techniques including spectral analysis of heart rate variability and Finapres blood pressure monitoring.
• Measured muscle sympathetic nerve activity.
• Employed radionuclide tests and animal models of obstructive sleep apnoea.

Main Results:

• Acute haemodynamic changes in OSA are linked to heightened sympathetic discharge and fluctuating parasympathetic activity.
• Chronic alterations include impaired baroreceptor and chemoreceptor reflexes, increased daytime sympathetic activity, and abnormal vagal responses.
• Acute autonomic changes are triggered by hypoxaemia, upper airway responses, ventilatory changes, and arousal.

Conclusions:

• CPAP therapy effectively mitigates acute cardiovascular changes and reduces sympathetic over-activity in OSA patients.
• CPAP can restore abnormal vagal responses and decrease chronic sympathetic activity in compliant patients.
• The long-term impact of CPAP on reducing cardiovascular morbidity in OSA remains to be definitively established.