Valsalva maneuver: shortest optimal expiratory strain duration

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Function
• Respiratory Mechanics

Background:

• The Valsalva maneuver (VM) is a standard test for assessing autonomic nervous system (ANS) function.
• Understanding the impact of expiratory strain (ES) duration on hemodynamic responses is crucial for accurate interpretation.

Purpose of the Study:

• To quantify the perceived difficulty of performing the VM with varying ES durations.
• To determine the consistency of hemodynamic responses during the VM across different ES durations.

Main Methods:

• Thirty-four healthy subjects performed the VM with 10, 12, and 15-second ES durations in random order.
• Subjects rated the difficulty of each trial on a 1-10 scale.
• Continuous, non-invasive blood pressure and heart rate (HR) were recorded to analyze Valsalva ratio (VR), early and late phase II (IIE, IIL), tachycardia latency (TL), bradycardia latency (BL), and overshoot latency (OV-L).

Main Results:

• Perceived difficulty significantly increased with longer ES durations (p<0.001).
• Hemodynamic responses (IIE, TL, BL, OV-L, VR) and their variability remained consistent across ES durations.
• Late phase II (IIL) response increased significantly with longer ES durations and was poorly delineated in some trials at 10 seconds ES.

Conclusions:

• A 10-second ES duration during the VM is perceived as low difficulty in healthy individuals.
• This ES duration yields consistent hemodynamic responses for most parameters, except for the IIL phase.
• The absence or poor delineation of the IIL phase at 10 seconds ES should not be mistaken for sympathetic vasoconstrictor dysfunction.