Nonlinear measures of heart rate time series: influence of posture and controlled breathing

• Published in: Autonomic neuroscience Vol. 83; no. 3; pp. 148 - 158
• Main Authors: Radhakrishna, R.K.A., Narayana Dutt, D., Yeragani, Vikram Kumar
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 02-10-2000; Elsevier
• Subjects: Adult; Autonomic Nervous System - physiology; Biological and medical sciences; Blood vessels and receptors; Breathing; Chaos; Female; Fundamental and applied biological sciences. Psychology; Heart Rate - physiology; Heart rate variability; Humans; Male; Models, Cardiovascular; Nonlinear; Nonlinear Dynamics; Posture; Posture - physiology; Predictive Value of Tests; Reference Values; Reproducibility of Results; Respiration; Signal Processing, Computer-Assisted; Spectral; Time Factors; Vertebrates: cardiovascular system; Chaos; Nonlinear; Spectral; Breathing; Heart rate variability; Posture; Human; Heart rate; Time series; Nonlinearity; Respiration; Spectral analysis
• ISSN: 1566-0702; 1872-7484
• DOI: 10.1016/S1566-0702(00)00173-9

In this study, we investigated measures of nonlinear dynamics and chaos theory in regards to heart rate variability in 27 normal control subjects in supine and standing postures, and 14 subjects in spontaneous and controlled breathing conditions. We examined minimum embedding dimension (MED), largest Lyapunov exponent (LLE) and measures of nonlinearity (NL) of heart rate time series. MED quantifies the system’s complexity, LLE predictability and NL, a measure of deviation from linear processes. There was a significant decrease in complexity (
P<0.00001), a decrease in predictability (
P<0.00001) and an increase in nonlinearity (
P=0.00001) during the change from supine to standing posture. Decrease in MED, and increases in NL score and LLE in standing posture appear to be partly due to an increase in sympathetic activity of the autonomous nervous system in standing posture. An improvement in predictability during controlled breathing appears to be due to the introduction of a periodic component.