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Leg elevation compared with Trendelenburg position: effects on autonomic cardiac control
G J McHugh1, B J Robinson, D C Galletly
1Section of Anaesthesia, Wellington School of Medicine, New Zealand.
British Journal of Anaesthesia
|December 1, 1994
Summary
Body position changes, including head-down tilt and leg elevation, do not significantly alter heart rate variability or cardiac autonomic control in healthy males. These findings suggest parasympathetic cardiac control remains stable across different resting postures.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Function
- Human Physiology Research
Background:
- Understanding the impact of body positioning on cardiovascular regulation is crucial for various physiological and clinical contexts.
- Autonomic nervous system (ANS) modulates heart rate and vascular function, and its response to postural changes warrants investigation.
- Previous research has explored postural effects on circulation, but detailed analysis of spectral components of heart rate and vascular variability is less common.
Purpose of the Study:
- To investigate the effects of head-down tilt and leg elevation on heart rate variability (HRV) and finger plethysmographic amplitude variability.
- To compare autonomic cardiac control across three distinct body positions: head-down tilt, supine, and supine with leg elevation.
- To determine if these postural changes significantly alter parasympathetic cardiac control compared to a standard resting supine position.
Main Methods:
- Study involved 12 healthy male volunteers.
- Measurements included spectral analysis of heart rate and finger plethysmographic amplitude variability.
- Three body positions were tested: 10° head-down tilt, horizontal supine, and supine with 50 cm leg elevation.
Main Results:
- No statistically significant differences were observed in any time or frequency domain measures of heart rate variability between the three positions.
- Similarly, no significant differences were found in spectral components of finger plethysmographic amplitude variability across the tested body positions.
- The dominant parasympathetic cardiac control remained unaltered in head-down tilt and leg elevation positions compared to the supine position.
Conclusions:
- Neither 10° head-down tilt nor 50 cm leg elevation significantly alters heart rate variability or finger plethysmographic amplitude variability in healthy males.
- These postural changes do not induce significant modifications in the dominant parasympathetic cardiac control.
- The findings suggest that the resting supine position is a reliable baseline for assessing cardiac autonomic function, unaffected by moderate head-down tilt or leg elevation.