IMPORTANT INFLUENCE OF RESPIRATION ON HUMAN R-R INTERVAL POWER SPECTRA IS LARGELY IGNORED

Frequency-domain analyses of R-R intervals are used widely to estimate levels of autonomic neural traffic to the human heart. Because respir ation modulates autonomic activity, we determined for nine healthy sub jects the influence of breathing frequency and tidal volume on R-R int erval 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 volum es 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 signific antly greater at a tidal volume of 1,500 than 1,000 ml. Neither breath ing frequency nor tidal volume influenced average R-R intervals signif icantly. Our review of studies reporting human R-R interval power spec tra showed that 51% of the studies controlled respiratory rate, 11% co ntrolled tidal volume, and 11% controlled both respiratory rate and ti dal volume. The major implications of our analyses are that breathing parameters strongly influence low-frequency as well as respiratory fre quency R-R interval power spectra and that this influence is largely i gnored in published research.