Noninvasive methods to study autonomic nervous control of circulation

Area of Science:

• Physiology
• Autonomic Nervous System Function
• Cardiovascular Regulation

Background:

• The autonomic nervous system regulates skin blood flow and heart rate variability through complex afferent and efferent pathways.
• Understanding the interplay between thermal, postural, and sensory stimulations is crucial for elucidating cardiovascular control mechanisms.

Purpose of the Study:

• To investigate the neural mechanisms mediating thermally entrained oscillations in forearm skin blood flow.
• To examine the effects of postural and thermal stimulations on cardiovascular variability.
• To assess autonomic nervous system function in various clinical populations using heart rate variability analysis.

Main Methods:

• Analysis of forearm skin blood flow oscillations using frequency domain methods (0.01-0.10 Hz).
• Evaluation of heart rate variability (HRV) during thermal, postural, Valsalva, and diving reflex tests.
• Power spectral density analysis of heart rate to quantify respiratory and other influences.

Main Results:

• Nervous afferentation and efferentation mediated thermally entrained skin blood flow oscillations.
• Postural changes altered skin blood flow, with thermal stimulation interacting with this effect.
• Thermal, postural, and sensory stimulations selectively affected HRV at specific frequencies.
• Neonatal heart rate showed frequency-selective thermal entrainment, increasing with maturity.
• Deep breathing and intermittent tilting influenced HRV, with power spectral density being a precise measure.
• Children with juvenile diabetes and rheumatoid arthritis exhibited normal vagal control of HRV.
• Exaggerated sympathetic cardiac inotropic control was observed in various autonomic tests.
• Inhibited vagal modulation and exaggerated sympathetic reactivity were noted in subjects with dystonic symptoms and orthostatic intolerance.

Conclusions:

• Autonomic nervous system pathways significantly modulate cardiovascular responses to thermal and postural challenges.
• HRV analysis provides valuable insights into autonomic function, particularly in clinical populations.
• Specific autonomic dysfunctions, such as in orthostatic intolerance, are characterized by altered sympathetic and vagal modulation.