Respiratory modulation of human autonomic rhythms

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 280; no. 6; p. H2674
• Main Authors: Badra, L J, Cooke, W H, Hoag, J B, Crossman, A A, Kuusela, T A, Tahvanainen, K U, Eckberg, D L
• Format: Journal Article
• Language: English
• Published: United States 01-06-2001
• Subjects: Adult; Apnea - metabolism; Autonomic Nervous System - drug effects; Autonomic Nervous System - physiology; Baroreflex - drug effects; Baroreflex - physiology; Blood Pressure - drug effects; Blood Pressure - physiology; Diastole - drug effects; Diastole - physiology; Female; Fourier Analysis; Heart Rate - physiology; Humans; Hyperventilation - metabolism; Male; Oxygen - metabolism; Oxygen - pharmacology; Periodicity; Plethysmography; Pulmonary Gas Exchange; Respiration; Respiratory Physiological Phenomena - drug effects; Signal Processing, Computer-Assisted; Supine Position; Systole - drug effects; Systole - physiology; Vagus Nerve - physiology; NASA Discipline Cardiopulmonary; Non-NASA Center
• ISSN: 0363-6135
• DOI: 10.1152/ajpheart.2001.280.6.h2674

We studied the influence of three types of breathing [spontaneous, frequency controlled (0.25 Hz), and hyperventilation with 100% oxygen] and apnea on R-R interval, photoplethysmographic arterial pressure, and muscle sympathetic rhythms in nine healthy young adults. We integrated fast Fourier transform power spectra over low (0.05-0.15 Hz) and respiratory (0.15-0.3 Hz) frequencies; estimated vagal baroreceptor-cardiac reflex gain at low frequencies with cross-spectral techniques; and used partial coherence analysis to remove the influence of breathing from the R-R interval, systolic pressure, and muscle sympathetic nerve spectra. Coherence among signals varied as functions of both frequency and time. Partialization abolished the coherence among these signals at respiratory but not at low frequencies. The mode of breathing did not influence low-frequency oscillations, and they persisted during apnea. Our study documents the independence of low-frequency rhythms from respiratory activity and suggests that the close correlations that may exist among arterial pressures, R-R intervals, and muscle sympathetic nerve activity at respiratory frequencies result from the influence of respiration on these measures rather than from arterial baroreflex physiology. Most importantly, our results indicate that correlations among autonomic and hemodynamic rhythms vary over time and frequency, and, thus, are facultative rather than fixed.