Short Term Heart Rate Variability on the ESA-Short Arm Human Centrifuge
- Paper number
IAC-07-A1.3.-A1.4.03
- Author
Prof. Floris Wuyts, University of Antwerp, Belgium
- Year
2007
- Abstract
The ESA short arm human centrifuge (SAHC - constructed by Verhaert Space (BE)) contains 2 bed nacelles and 2 chairs that are radially oriented. In supine position lying on the horizontally oriented bed, the heart was typically situated at 1.05 m from the center of rotation. Depending on each subject, rotations were set at 24, 29 and 32 rpm to obtain respectively 0.7Gz (radial oriented), 1Gz and 1.2 Gz at heart level. This yielded at the head center values of approximately 0.47, 0.66 and 0.80 Gz and at the feet 1.5, 2.2 and 2.6 Gz respectively. By means of a canopy placed over the upper part of the body, a dark environment was obtained for the subjects. Subjects were equipped with a head set with microphone and head phones to communicate with the operator in the control room. IRB approval was obtained and Informed Consent signed by the subjects. Electrocardiogram, respiration and continuous blood pressure were recorded from 7 healthy male control subjects. A series of 3 imposed and controlled breathing protocols (6, 9 and 15 breaths per minute for 9 breaths) for 180s, was repeated 5 times during 3 different g-load conditions (0.7, 1 and 1.2 Gz). In between, a one minute break was inserted for lower limb exercises. Control measurements in erect and supine position were obtained. The response of the Autonomic Nervous System (ANS) to the orthostatic challenge induced by the different g-loads was assessed through the analysis of heart rate variability (HRV). Hereto, a short-term time domain algorithm [1] was used to compute the amplitude of the respiratory sinus arrhythmia (RSA) which is the high frequency component of HRV and a well recognized marker of vagal control. Our results show that the g-load induced blood pooling induced increased HR (sympathetic activation) and decreased RSA amplitude (vagal withdrawal). As such, the response of the ANS to the orthostatic challenge can be monitored by means of RSA analysis during short (<180s) controlled breathing protocols. The Gz-gradient is an important factor of orthostatic challenge, since at a moderate 1.2 Gz at the heart, yet 2.6 Gz at the feet, HR was significantly increased. This study demonstrates the usefulness of the ESA-SAHC as a model for the adaptation of cardiovascular control to different G-load gradients. This research was supported by the PRODEX program managed by the European Space Agency in collaboration with the Belgian Federal Science Policy Office. [1]. Migeotte et al. Am J Physiol – Heart Circ Physiol, 284, H1995-06,2003.
Authors: F. WUYTS, R. VANSPAUWEN, P. VAN DE HEYNING, P-F. MIGEOTTE#
Antwerp University Research center for Equilibrium and Aerospace. University of Antwerp, Belgium. # Biomedical Physics Laboratory. Universite Libre de Bruxelles, Belgium. Floris.Wuyts@ua.ac.be
- Abstract document