System dynamics of active and passive postural changes: Insights from principal dynamic modes analysis of baroreflex loop

• Published in: Computers in biology and medicine Vol. 100; pp. 27 - 35
• Main Authors: Shahzad, Tariq, Saleem, Saqib, Usman, Saeeda, Mirza, Jawad, Islam, Qamar-ul, Ouahada, Khmaies, Marwala, Tshilidzi
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.09.2018; Elsevier Limited
• Subjects: Adult; Associated nonlinear function; Baroreceptors; Baroreflex; Baroreflex - physiology; Blood pressure; Blood Pressure - physiology; Cardiac arm; Cardiovascular system; Datasets; Electrocardiography; Feedback; Female; Frequencies; Heart rate; Heart Rate - physiology; Humans; Hypotension; Male; Mechanical arm; Models, Cardiovascular; Physiology; Posture; Posture - physiology; Pressure sensors; Principal dynamic modes; R-R interval; Reflexes; System dynamics; System identification; Time series; R-R interval; Mechanical arm; Cardiac arm; Baroreflex; Blood pressure; Principal dynamic modes; Associated nonlinear function
• ISSN: 0010-4825; 1879-0534; 1879-0534
• DOI: 10.1016/j.compbiomed.2018.06.022

The baroreflex being a key modulator of cardiovascular control ensures adequate blood pressure regulation under orthostatic stress which otherwise may cause severe hypotension. Contrary to conventional baroreflex sensitivity indices derived across a-priori traditional frequency bands, the present study is aimed at proposing new indices for the assessment of baroreflex drive which follows active (supine to stand-up) and passive (supine to head-up tilt) postural changes. To achieve this, a novel system identification approach of principal dynamic modes (PDM) was utilized to extract data-adaptive frequency components of closed-loop interactions between beat-to-beat interval and systolic blood pressure recorded from 10 healthy humans. We observed that the gain of low-pass global PDM of cardiac arm (:feedback reflex loop, mediated by pressure sensors to adjust heart rate in response to arterial blood pressure), and 0.2 Hz global PDM of mechanical arm (:feed-forward pathways, originating changes in arterial blood pressure in response to heart rate variations) may function as potential markers to distinguish active and passive orthostatic tests in healthy subjects. •Arterial baroreflex ensures blood pressure regulation.•Novel indices are proposed for baroreflex role in orthostatic tests.•Cardiac and mechanical arms of baroreflex interact in a closed-loop fashion.•Both arms contribute along different frequency dynamics for postural challenges.