Important influence of respiration on human R-R interval power spectra is largely ignored

TLDR

Frequency‑domain analyses of R‑R intervals are widely used to estimate autonomic neural traffic to the human heart. The study aimed to determine how breathing frequency and tidal volume influence R‑R interval power spectra in nine healthy subjects using fast‑Fourier transform. We recorded R‑R intervals while subjects breathed at seven rates (6–24 breaths/min) and two tidal volumes (1,000 and 1,500 ml) and surveyed the literature to assess current respiratory‑control practices. R‑R interval power at respiratory and low frequencies decreased with higher breathing rates and increased with larger tidal volumes, while average R‑R intervals were unchanged; a review showed only 51 % of studies controlled respiratory rate, 11 % tidal volume, and 11 % both, highlighting that breathing parameters strongly affect R‑R power spectra yet are largely ignored.

Abstract

Frequency-domain analyses of R-R intervals are used widely to estimate levels of autonomic neural traffic to the human heart. Because respiration modulates autonomic activity, we determined for nine healthy subjects the influence of breathing frequency and tidal volume on R-R interval power spectra (fast-Fourier transform method). We also surveyed published literature to determine current practices in this burgeoning field of scientific inquiry. Supine subjects breathed at rates of 6, 7.5, 10, 15, 17.1, 20, and 24 breaths/min and with nominal tidal volumes of 1,000 and 1,500 ml. R-R interval power at respiratory and low (0.06–0.14 Hz) frequencies declined significantly as breathing frequency increased. R-R interval power at respiratory frequencies was significantly greater at a tidal volume of 1,500 than 1,000 ml. Neither breathing frequency nor tidal volume influenced average R-R intervals significantly. Our review of studies reporting human R-R interval power spectra showed that 51% of the studies controlled respiratory rate, 11% controlled tidal volume, and 11% controlled both respiratory rate and tidal volume. The major implications of our analyses are that breathing parameters strongly influence low-frequency as well as respiratory frequency R-R interval power spectra and that this influence is largely ignored in published research.