Title :
Variability of the maximal amplitudes of impedance cardiogram and of its first derivative during supine, standing, paced breathing, and exercise maneuvers
Author :
Carrasco-Sosa, Salvador ; Guillen-Mandujano, Alejandra
Author_Institution :
Div. de Cienc. Biologicas y de la Salud, Univ. Autonoma Metropolitana-I, Mexico City, Mexico
Abstract :
Beat-to-beat variability of the maximal amplitudes of thoracic impedance (ΔZmax) and of its first derivative (dZ/dtmax) remain unexplored. We examined the effects of four maneuvers eliciting different sympathetic activity levels on ΔZmax and dZ/dtmax time-frequency spectral measures. Seventeen healthy subjects performed 5-min maneuvers: lying, controlled breathing, standing (S) and exercise (E). Time-frequency spectra of RR intervals (RR), ΔZmax, dZ/dtmax and respiration (Res) time series were estimated to compute their low-frequency (LFΔZmax, LFdZ/dtmax) and high-frequency powers (HFRR, HFΔZmax, HFdZ/dtmax, HFRes) and the time-frequency coherences of HFRes with HFΔZmax and HFdZ/dtmax. HFRR and RR level decreased in S and E. LFΔZmax was negligible. HFΔZmax was maximal in E and showed significant coherences with HFRes. LFdZ/dtmax was maximal in E and decreased in S. HFdZ/dtmax was much greater than LFdZ/dtmax and showed significant coherences with HFRes. Because LFdZ/dtmax power is cardiac sympathetic activity and stroke volume dependent, it can be considered a noninvasive index of global left ventricular systolic function. HFdZ/dtmax power is originated by thoracic volume changes. The mechanical respiratory effect is the main source of ΔZmax and dZ/dtmax time series variability.
Keywords :
electrocardiography; medical signal detection; pneumodynamics; time series; beat-to-beat variability; exercise maneuver; frequency spectral measures; global left ventricular systolic function; impedance cardiogram; maximal amplitude variability; mechanical respiratory effect; paced breathing maneuver; standing maneuver; stroke volume dependence; supine maneuver; sympathetic activity level; thoracic impedance; thoracic volume changes; time series; Abstracts; Discrete wavelet transforms; Protocols;
Conference_Titel :
Computing in Cardiology Conference (CinC), 2014
Print_ISBN :
978-1-4799-4346-3