Dissecting Cardiovascular Responses to a Fixed-Interval Volitional Sighing Protocol Using a Mixed Modeling Approach.

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Function
• Respiratory Regulation

Background:

• Sighing elicits a sympathetic cardiovascular response, similar to exercise.
• This response has potential for use in graded stress testing to identify preclinical cardiovascular changes.
• Current methods for assessing cardiovascular stress reactivity may not be universally accessible or sensitive to early dysfunction.

Purpose of the Study:

• To introduce and validate the fixed-interval volitional sighing (FIVS) protocol for cardiovascular stress testing.
• To characterize cardiovascular and autonomic responses to FIVS at varying sighing frequencies.
• To explore sex-based differences in responses to the FIVS protocol.

Main Methods:

• Developed the fixed-interval volitional sighing (FIVS) protocol, pacing sighs at 30-second and 15-second intervals.
• Recruited 250 healthy college students (65% female) to undergo baseline and FIVS tasks.
• Continuously measured heart rate (HR), blood pressure, and respiration, analyzing responses using mixed models.

Main Results:

• FIVS significantly increased HR, low-frequency heart rate variability (LF-HRV), pulse transit time variability (PTTv), mean arterial pressure (MAP), and low-frequency blood pressure variability (LF-BPV).
• Responses were more pronounced with shorter sighing intervals (15s vs. 30s), indicating a dose-dependent effect.
• Males showed greater increases in sympathetic indices (HR, LF-HRV, LF-BPV, PTTv) compared to females, who had smaller decreases in high-frequency HRV (HF-HRV).

Conclusions:

• Volitional sighing, via the FIVS protocol, effectively induces sympathetic activation and cardiovascular changes.
• The FIVS protocol demonstrates graded responses based on sighing frequency and intensity.
• Detected sex differences suggest FIVS can identify individual variations in cardiovascular reactivity, potentially serving as an accessible stress test for early dysfunction detection.