Cardiovascular and neuroendocrine responses to left lateral position in non-obese young males

Area of Science:

• Cardiovascular Physiology
• Human Physiology
• Hemodynamics

Background:

• Previous research indicated heart distension in the left lateral position (LAT) compared to the supine (SUP) position.
• Cardiopulmonary low-pressure receptor stimulation was hypothesized to induce peripheral vasodilation, potentially altering cardiovascular dynamics.

Purpose of the Study:

• To test the hypothesis that LAT increases cardiac output.
• To investigate if mean arterial pressure is maintained or decreased in LAT via vasodilation.
• To determine the hydrostatic reference point for arterial pressure measurements in SUP and LAT.

Main Methods:

• Twelve healthy young males participated in the study.
• Cardiac output was measured using foreign gas rebreathing.
• Arterial pressures were measured at the brachial artery and finger; hydrostatic reference points were determined using magnetic resonance imaging.

Main Results:

• Cardiac output, heart rate, and plasma vasoactive hormone concentrations remained unchanged between SUP and LAT.
• Mean arterial pressures at the brachial and finger levels were unaffected by the positional change.
• The hydrostatic reference point for arterial pressure measurement was located 1/3 of the anteroposterior chest diameter below the sternum in SUP and 2.5 cm below the midsternal level in LAT.

Conclusions:

• Thirty minutes in the left lateral position did not significantly affect cardiac output, mean arterial pressures, or vasoactive hormone release in young males.
• The findings suggest that positional changes alone do not elicit significant compensatory cardiovascular responses in healthy individuals.
• Accurate determination of hydrostatic reference points is crucial for consistent arterial pressure measurements across different body positions.