INFLUENCE OF RESPIRATION ON METABOLIC, HEMODYNAMIC, PSYCHOMETRIC, ANDR-R INTERVAL POWER SPECTRAL PARAMETERS

Because respiration modulates autonomic activity, we determined the ma gnitude of perturbation of changing breathing frequency and tidal volu me on metabolic, hemodynamic, psychometric, and R-R interval power spe ctral parameters. Seated subjects breathed at three different rates an d five different volumes with each of the different rates. Breathing r ates and volumes were percentages of the subject's resting breathing p attern and, therefore, identical across all subjects. Increases in rat e and volume resulted in significant perturbations in end-tidal CO2 pr oduction, CO2 production, ventilatory equivalent for O-2, comfort leve ls, and R-R interval power spectra (P < 0.05). The magnitude of the pe rturbations in the above parameters indicated a substantial upset in a ll subjects' metabolic, hemodynamic, and comfort homeostasis, precipit ating a significant loss of vagal tone. The implications of our findin gs are that imposed breathing patterns used to modulate autonomic outf low should be tailored to the individual's resting breathing pattern. These data further support the urgent need for concomitant metabolic a nd respiratory measurements when analyzing and interpreting heart rate variability data.