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Porta A, Gelpi F, Bari V, Cairo B, De Maria B, Tonon D, Rossato G, Faes L. Concomitant evaluation of cardiovascular and cerebrovascular controls via Geweke spectral causality to assess the propensity to postural syncope. Med Biol Eng Comput 2023; 61:3141-3157. [PMID: 37452270 PMCID: PMC10746785 DOI: 10.1007/s11517-023-02885-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Accepted: 07/05/2023] [Indexed: 07/18/2023]
Abstract
The evaluation of propensity to postural syncope necessitates the concomitant characterization of the cardiovascular and cerebrovascular controls and a method capable of disentangling closed loop relationships and decomposing causal links in the frequency domain. We applied Geweke spectral causality (GSC) to assess cardiovascular control from heart period and systolic arterial pressure variability and cerebrovascular regulation from mean arterial pressure and mean cerebral blood velocity variability in 13 control subjects and 13 individuals prone to develop orthostatic syncope. Analysis was made at rest in supine position and during head-up tilt at 60°, well before observing presyncope signs. Two different linear model structures were compared, namely bivariate autoregressive and bivariate dynamic adjustment classes. We found that (i) GSC markers did not depend on the model structure; (ii) the concomitant assessment of cardiovascular and cerebrovascular controls was useful for a deeper comprehension of postural disturbances; (iii) orthostatic syncope appeared to be favored by the loss of a coordinated behavior between the baroreflex feedback and mechanical feedforward pathway in the frequency band typical of the baroreflex functioning during the postural challenge, and by a weak cerebral autoregulation as revealed by the increased strength of the pressure-to-flow link in the respiratory band. GSC applied to spontaneous cardiovascular and cerebrovascular oscillations is a promising tool for describing and monitoring disturbances associated with posture modification.
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Affiliation(s)
- Alberto Porta
- Department of Biomedical Sciences for Health, University of Milan, 20133, Milan, Italy.
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Via R. Morandi 30, San Donato Milanese, 20097, Milan, Italy.
| | - Francesca Gelpi
- Department of Biomedical Sciences for Health, University of Milan, 20133, Milan, Italy
| | - Vlasta Bari
- Department of Biomedical Sciences for Health, University of Milan, 20133, Milan, Italy
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Via R. Morandi 30, San Donato Milanese, 20097, Milan, Italy
| | - Beatrice Cairo
- Department of Biomedical Sciences for Health, University of Milan, 20133, Milan, Italy
| | | | - Davide Tonon
- Department of Neurology, IRCCS Sacro Cuore Don Calabria Hospital, 37024, Negrar, Verona, Italy
| | - Gianluca Rossato
- Department of Neurology, IRCCS Sacro Cuore Don Calabria Hospital, 37024, Negrar, Verona, Italy
| | - Luca Faes
- Department of Engineering, University of Palermo, 90128, Palermo, Italy
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2
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Thuptimdang W, Chalacheva P, Coates TD, Khoo MC. McDAPS: A multi-channel physiological signals display and analysis system for clinical researchers. SOFTWAREX 2023; 23:101482. [PMID: 38009083 PMCID: PMC10673622 DOI: 10.1016/j.softx.2023.101482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/28/2023]
Abstract
We introduce McDAPS, an interactive software for assessing autonomic imbalance from non-invasive multi-channel physiological recordings. McDAPS provides a graphical user interface for data visualization, beat-to-beat processing and interactive analyses. The software extracts beat-to-beat RR interval systolic blood pressure, diastolic blood pressure, the pulse amplitude of photoplethysmogram and the pulse-to-pulse interval. The analysis modules include stationary and time-varying power spectral analyses, moving-correlation analysis and univariate analyses. Analyses can also be performed in batch mode if multiple datasets have to be processed in the same way. The program exports results in standard CSV format. McDAPS runs in MATLAB, and is supported on MS Windows and MAC OS systems. The MATLAB source code is available at https://github.com/thuptimd/McDAPS.git.
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Affiliation(s)
- Wanwara Thuptimdang
- Institute of Biomedical Engineering, Department of Biomedical Sciences and Biomedical Engineering, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand
| | - Patjanaporn Chalacheva
- Biomedical Engineering Department, Carnegie Mellon University, Pittsburgh, PA, United States of America
| | - Thomas D. Coates
- Hematology Section, Cancer and Blood Disease Institute, Children’s Hospital Los Angeles, University of Southern California Keck School of Medicine, Los Angeles, CA, United States of America
| | - Michael C.K. Khoo
- Department of Biomedical Engineering, University of Southern California, Los Angeles, United States of America
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3
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O'Leary DS, Mannozzi J, Augustyniak RA, Ichinose M, Spranger MD. Hypertension depresses arterial baroreflex control of both heart rate and cardiac output during rest, exercise, and metaboreflex activation. Am J Physiol Regul Integr Comp Physiol 2022; 323:R720-R727. [PMID: 36121147 PMCID: PMC9602692 DOI: 10.1152/ajpregu.00093.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 08/24/2022] [Accepted: 09/08/2022] [Indexed: 01/19/2023]
Abstract
Rapid regulation of arterial blood pressure on a beat-by-beat basis occurs primarily via arterial baroreflex control of cardiac output (CO) via rapid changes in heart rate (HR). Previous studies have shown that changes in HR do not always cause changes in CO, because stroke volume may vary. Whether these relationships are altered in hypertension is unknown. Using the spontaneous baroreflex sensitivity (SBRS) approach, we investigated whether baroreflex control of HR and CO were impaired after the induction of hypertension in conscious, chronically instrumented canines at rest, during mild exercise, and during exercise with metaboreflex activation (induced via reductions in hindlimb blood flow) both before and after induction of hypertension (induced via a modified Goldblatt approach-unilateral reduction in renal blood flow to ∼30% of control values until systolic pressure ≥ 140 mmHg and a diastolic pressure ≥ 90 mmHg for >30 days). After induction of hypertension, SBRS control of both HR and CO was reduced in all settings. In control, only about 50% of SBRS changes in HR caused changes in CO. This pattern was sustained in hypertension. Thus, in hypertension, the reduced SBRS in the control of HR caused reduced SBRS control of CO and this likely contributes to the increased incidence of orthostatic hypotension seen in hypertensive patients.
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Affiliation(s)
- Donal S O'Leary
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Joseph Mannozzi
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Robert A Augustyniak
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Masashi Ichinose
- Human Integrative Physiology Laboratory, School of Business Administration, Meiji University, Tokyo, Japan
| | - Marty D Spranger
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
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4
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Padhye N, Rios D, Fay V, Hanneman SK. Pressure Injury Link to Entropy of Abdominal Temperature. ENTROPY (BASEL, SWITZERLAND) 2022; 24:1127. [PMID: 36010790 PMCID: PMC9407490 DOI: 10.3390/e24081127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 08/05/2022] [Accepted: 08/08/2022] [Indexed: 06/15/2023]
Abstract
This study examined the association between pressure injuries and complexity of abdominal temperature measured in residents of a nursing facility. The temperature served as a proxy measure for skin thermoregulation. Refined multiscale sample entropy and bubble entropy were used to measure the irregularity of the temperature time series measured over two days at 1-min intervals. Robust summary measures were derived for the multiscale entropies and used in predictive models for pressure injuries that were built with adaptive lasso regression and neural networks. Both types of entropies were lower in the group of participants with pressure injuries (n=11) relative to the group of non-injured participants (n=15). This was generally true at the longer temporal scales, with the effect peaking at scale τ=22 min for sample entropy and τ=23 min for bubble entropy. Predictive models for pressure injury on the basis of refined multiscale sample entropy and bubble entropy yielded 96% accuracy, outperforming predictions based on any single measure of entropy. Combining entropy measures with a widely used risk assessment score led to the best prediction accuracy. Complexity of the abdominal temperature series could therefore serve as an indicator of risk of pressure injury.
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5
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Taboni A, Fagoni N, Fontolliet T, Vinetti G, Ferretti G. Dynamics of cardiovascular and baroreflex readjustments during a light-to-moderate exercise transient in humans. Eur J Appl Physiol 2022; 122:2343-2354. [PMID: 35861802 PMCID: PMC9561001 DOI: 10.1007/s00421-022-05011-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 07/07/2022] [Indexed: 12/02/2022]
Abstract
Purpose We hypothesised that, during a light-to-moderate exercise transient, compared to an equivalent rest-to-exercise transient, (1) a further baroreflex sensitivity (BRS) decrease would be slower, (2) no rapid heart rate (HR) response would occur, and (3) the rapid cardiac output (CO) response would have a smaller amplitude (A1). Hence, we analysed the dynamics of arterial baroreflexes and the HR and CO kinetics during rest-to-50 W (0–50 W) and 50-to-100 W (50–100 W) exercise transients. Methods 10 subjects performed three 0–50 W and three 50–100 W on a cycle ergometer. We recorded arterial blood pressure profiles (photo-plethysmography) and R-to-R interval (RRi, electrocardiography). The former were analysed to obtain beat-by-beat mean arterial pressure (MAP) and stroke volume (SV). CO was calculated as SV times HR. BRS was measured by modified sequence method. Results During 0–50 W, MAP transiently fell (− 9.0 ± 5.7 mmHg, p < 0.01) and BRS passed from 15.0 ± 3.7 at rest to 7.3 ± 2.4 ms mmHg−1 at 50 W (p < 0.01) promptly (first BRS sequence: 8.1 ± 4.6 ms mmHg−1, p < 0.01 vs. rest). During 50–100 W, MAP did not fall and BRS passed from 7.2 ± 2.6 at 50 W to 3.3 ± 1.3 ms mmHg−1 at 100 W (p < 0.01) slowly (first BRS sequence: 5.3 ± 3.1 ms mmHg−1, p = 0.07 vs. 50 W). A1 for HR was 9.2 ± 6.0 and 6.0 ± 4.5 min−1 in 0–50 W and 50–100 W, respectively (p = 0.19). The corresponding A1 for CO were 2.80 ± 1.54 and 0.91 ± 0.55 l∙min−1 (p < 0.01). Conclusion During 50–100 W, with respect to 0–50 W, BRS decreased more slowly, in absence of a prompt pressure decrease. BRS decrease and rapid HR response in 50–100 W were unexpected and ascribed to possible persistence of some vagal tone at 50 W. Supplementary Information The online version contains supplementary material available at 10.1007/s00421-022-05011-4.
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Affiliation(s)
- Anna Taboni
- Department of Anaesthesiology, Pharmacology, Intensive Care, and Emergencies, University of Geneva, Geneva, Switzerland
| | - Nazzareno Fagoni
- Department of Anaesthesiology, Pharmacology, Intensive Care, and Emergencies, University of Geneva, Geneva, Switzerland.,Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy.,AAT Brescia, Department of Anaesthesiology, Intensive Care and Emergency Medicine, Spedali Civili University Hospital, Brescia, Italy
| | - Timothée Fontolliet
- Department of Anaesthesiology, Pharmacology, Intensive Care, and Emergencies, University of Geneva, Geneva, Switzerland
| | - Giovanni Vinetti
- Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy. .,Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.
| | - Guido Ferretti
- Department of Anaesthesiology, Pharmacology, Intensive Care, and Emergencies, University of Geneva, Geneva, Switzerland.,Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy
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6
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Thuptimdang W, Shah P, Khaleel M, Sunwoo J, Veluswamy S, Kato RM, Coates TD, Khoo MCK. Vasoconstriction Response to Mental Stress in Sickle Cell Disease: The Role of the Cardiac and Vascular Baroreflexes. Front Physiol 2021; 12:698209. [PMID: 34803725 PMCID: PMC8599360 DOI: 10.3389/fphys.2021.698209] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 10/15/2021] [Indexed: 11/13/2022] Open
Abstract
Recent studies have shown that individuals with sickle cell disease (SCD) exhibit greater vasoconstriction responses to physical autonomic stressors, such as heat pain and cold pain than normal individuals, but this is not the case for mental stress (MTS). We sought to determine whether this anomalous finding for MTS is related to inter-group differences in baseline cardiac and vascular autonomic function. Fifteen subjects with SCD and 15 healthy volunteers participated in three MTS tasks: N-back, Stroop, and pain anticipation (PA). R-R interval (RRI), arterial blood pressure and finger photoplethysmogram (PPG) were continuously monitored before and during these MTS tasks. The magnitude of vasoconstriction was quantified using change in PPG amplitude (PPGa) from the baseline period. To represent basal autonomic function, we assessed both cardiac and vascular arms of the baroreflex during the baseline period. Cardiac baroreflex sensitivity (BRSc) was estimated by applying both the "sequence" and "spectral" techniques to beat-to-beat measurements of systolic blood pressure and RRIs. The vascular baroreflex sensitivity (BRSv) was quantified using the same approaches, modified for application to beat-to-beat diastolic blood pressure and PPGa measurements. Baseline BRSc was not different between SCD and non-SCD subjects, was not correlated with BRSv, and was not associated with the vasoconstriction responses to MTS tasks. BRSv in both groups was correlated with mean PPGa, and since both baseline PPGa and BRSv were lower in SCD, these results suggested that the SCD subjects were in a basal state of higher sympathetically mediated vascular tone. In both groups, baseline BRSv was positively correlated with the vasoconstriction responses to N-back, Stroop, and PA. After adjusting for differences in BRSv within and between groups, we found no difference in the vasoconstriction responses to all three mental tasks between SCD and non-SCD subjects. The implications of these findings are significant in subjects with SCD since vasoconstriction reduces microvascular flow and prolongs capillary transit time, increasing the likelihood for vaso-occlusive crisis (VOC) to be triggered by exposure to stressful events.
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Affiliation(s)
- Wanwara Thuptimdang
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States
| | - Payal Shah
- Hematology Section, Children's Center for Cancer, Blood Disease and Bone Marrow Transplantation, Children's Hospital Los Angeles, University of Southern California Keck School of Medicine, Los Angeles, CA, United States
| | - Maha Khaleel
- Hematology Section, Children's Center for Cancer, Blood Disease and Bone Marrow Transplantation, Children's Hospital Los Angeles, University of Southern California Keck School of Medicine, Los Angeles, CA, United States
| | - John Sunwoo
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States
| | - Saranya Veluswamy
- Hematology Section, Children's Center for Cancer, Blood Disease and Bone Marrow Transplantation, Children's Hospital Los Angeles, University of Southern California Keck School of Medicine, Los Angeles, CA, United States
| | - Roberta M Kato
- Division of Pulmonology, Children's Hospital Los Angeles, University of Southern California Keck School of Medicine, Los Angeles, CA, United States
| | - Thomas D Coates
- Hematology Section, Children's Center for Cancer, Blood Disease and Bone Marrow Transplantation, Children's Hospital Los Angeles, University of Southern California Keck School of Medicine, Los Angeles, CA, United States
| | - Michael C K Khoo
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States
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7
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Brusaca LA, Barbieri DF, Beltrame T, Milan-Mattos JC, Catai AM, Oliveira AB. Cardiac autonomic responses to different tasks in office workers with access to a sit-stand table - a study in real work setting. ERGONOMICS 2021; 64:354-365. [PMID: 32985949 DOI: 10.1080/00140139.2020.1830184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 09/23/2020] [Indexed: 06/11/2023]
Abstract
The aim of this study was to characterise the cardiac autonomic modulation of different office tasks performed by office workers with access to a sit-stand table. Heart rate variability (HRV) of 24 office workers was measured for two hours during three days in the last week of sit-stand table use. HRV indexes and the percentage of heart rate reserve (%HRR) were calculated during computer and non-computer work tasks while sitting or standing, non-computer tasks away from the work desk, and informal work breaks. All cardiac autonomic responses demonstrated a statistically significant interaction effect between the tasks (all p < 0.05) except for the logarithmically-transformed high frequency power (ln HF ms2; p = 0.14). Tasks performed while standing and away from the desk had higher sympathetic modulation; in addition, the observed higher %HRR demonstrated that these tasks were more physically demanding in comparison to other tasks. Practitioner Summary: Prior reports indicated benefits based on alternated body postures using sit-stand table. Nevertheless, the cardiac autonomic responses of different tasks performed by office workers are unknown. This cross-sectional study showed that different tasks stimulate the cardiac autonomic nervous system in different ways, which could bring positive effects to the cardiovascular system.
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Affiliation(s)
- Luiz Augusto Brusaca
- Department of Physical Therapy, Clinical and Occupational Kinesiology Laboratory, Federal University of São Carlos, Sao Carlos, Brazil
| | - Dechristian França Barbieri
- Department of Physical Therapy, Clinical and Occupational Kinesiology Laboratory, Federal University of São Carlos, Sao Carlos, Brazil
| | - Thomas Beltrame
- Department of Physical Therapy, Cardiovascular Physical Therapy Laboratory, Federal University of São Carlos, Sao Carlos, Brazil
- The Institute of Computing, University of Campinas - UNICAMP, São Paulo, Brazil
- Department of Physical Therapy, Universidade Ibirapuera - UNIB, São Paulo, Brazil
| | - Juliana Cristina Milan-Mattos
- Department of Physical Therapy, Cardiovascular Physical Therapy Laboratory, Federal University of São Carlos, Sao Carlos, Brazil
| | - Aparecida Maria Catai
- Department of Physical Therapy, Cardiovascular Physical Therapy Laboratory, Federal University of São Carlos, Sao Carlos, Brazil
| | - Ana Beatriz Oliveira
- Department of Physical Therapy, Clinical and Occupational Kinesiology Laboratory, Federal University of São Carlos, Sao Carlos, Brazil
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8
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Reyes Del Paso GA, Contreras-Merino AM, de la Coba P, Duschek S. The cardiac, vasomotor, and myocardial branches of the baroreflex in fibromyalgia: Associations with pain, affective impairments, sleep problems, and fatigue. Psychophysiology 2021; 58:e13800. [PMID: 33645659 DOI: 10.1111/psyp.13800] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Revised: 02/08/2021] [Accepted: 02/15/2021] [Indexed: 12/22/2022]
Abstract
This study investigated the cardiac, vasomotor, and myocardial branches of the baroreflex in fibromyalgia using the spontaneous sequence method. Systolic blood pressure (SBP), interbeat interval (IBI), stroke volume (SV), pre-ejection period (PEP), and total peripheral resistance (TPR) were continuously recorded in 40 fibromyalgia patients and 30 healthy individuals during a cold pressor test and a mental arithmetic task. Sequences of covariation between SBP and IBI (cardiac branch), SV and PEP (myocardial branch), and TPR (vasomotor branch) were identified. Baroreflex sensitivity (BRS) was represented by the slope of the regression line between values in the sequences; baroreflex effectiveness (BEI) was indexed by the proportion of progressive SBP changes that elicited reflex responses. Patients exhibited lower BRS in the three branches, lower BEI in the cardiac and vasomotor branches, and reduced reactivity in cardiac BRS and BEI, SBP, IBI, SV, and PEP. Moreover, BRS and BEI were inversely related to clinical pain, cold pressor pain, depression, trait anxiety, sleep problems, and fatigue. Reduced function of the three baroreflex branches implies diminished resources for autonomic inotropic, chronotropic, and vascular regulation in fibromyalgia. Blunted stress reactivity indicates a limited capacity for autonomic cardiovascular adjustment to situational requirements. The associations of BRS and BEI with pain perception may reflect the antinociceptive effects arising from baroreceptor afferents, where reduced baroreflex function may contribute to the hyperalgesia characterizing fibromyalgia. The associations with affective impairments, sleep problems, and fatigue suggest that baroreflex dysfunctions are also involved in the secondary symptoms of the disorder.
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Affiliation(s)
| | | | | | - Stefan Duschek
- Institute of Psychology, UMIT - University for Health Sciences, Medical Informatics and Technology, Hall in Tirol, Austria
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9
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Krohova J, Faes L, Czippelova B, Pernice R, Turianikova Z, Wiszt R, Mazgutova N, Busacca A, Javorka M. Vascular resistance arm of the baroreflex: methodology and comparison with the cardiac chronotropic arm. J Appl Physiol (1985) 2020; 128:1310-1320. [PMID: 32213110 DOI: 10.1152/japplphysiol.00512.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Baroreflex response consists of cardiac chronotropic (effect on heart rate), cardiac inotropic (on contractility), venous (on venous return) and vascular (on vascular resistance) arms. Because of the simplicity of its measurement, the cardiac chronotropic arm is most often analyzed. The aim was to introduce a method to assess the vascular baroreflex arm and to characterize its changes during stress. We evaluated the effect of orthostasis and mental arithmetics (MA) in 39 (22 women, 17 men; median age: 18.7 yr) and 36 (21 women, 15 men; 19.2 yr) healthy volunteers, respectively. We recorded systolic (SBP) and mean (MBP) blood pressure by volume-clamp method and R-R interval (RR) by ECG. Cardiac output (CO) was recorded by impedance cardiography. From MBP and CO, peripheral vascular resistance (PVR) was calculated. The directional spectral coupling and gain of cardiac chronotropic (SBP to RR) and vascular (SBP to PVR) arms were quantified. The strength of the causal coupling from SBP to PVR was significantly higher than that of SBP to RR coupling over the whole protocol (P < 0.001). Along both arms, the coupling was higher during orthostasis compared with the supine position (P < 0.001 and P = 0.006); no MA effect was observed. No significant changes in the spectral gain (ratio of RR or PVR change to a unit SBP change) across all phases were found (0.111 ≤ P ≤ 0.907). We conclude that changes in PVR are tightly coupled with SBP oscillations via the baroreflex, providing an approach for baroreflex vascular arm analysis with the potential to reveal new aspects of blood pressure dysregulation.NEW & NOTEWORTHY Baroreflex response consists of several arms, but the cardiac chronotropic arm (blood pressure changes evoking heart rate response) is usually analyzed. This study introduces a method to assess the vascular baroreflex arm with the continuous noninvasive measurement of peripheral vascular resistance as an output considering causality in the interaction between oscillations and slower dynamics of vascular tone changes. We conclude that although vascular baroreflex arm involvement becomes dominant during orthostasis, gain of this interaction is relatively stable.
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Affiliation(s)
- J Krohova
- Department of Physiology and Biomedical Centre Martin (BioMed Martin), Jessenius Faculty of Medicine, Comenius University, Martin, Slovakia
| | - L Faes
- Department of Engineering, University of Palermo, Palermo, Italy
| | - B Czippelova
- Department of Physiology and Biomedical Centre Martin (BioMed Martin), Jessenius Faculty of Medicine, Comenius University, Martin, Slovakia
| | - R Pernice
- Department of Engineering, University of Palermo, Palermo, Italy
| | - Z Turianikova
- Department of Physiology and Biomedical Centre Martin (BioMed Martin), Jessenius Faculty of Medicine, Comenius University, Martin, Slovakia
| | - R Wiszt
- Department of Physiology and Biomedical Centre Martin (BioMed Martin), Jessenius Faculty of Medicine, Comenius University, Martin, Slovakia
| | - N Mazgutova
- Department of Physiology and Biomedical Centre Martin (BioMed Martin), Jessenius Faculty of Medicine, Comenius University, Martin, Slovakia
| | - A Busacca
- Department of Engineering, University of Palermo, Palermo, Italy
| | - M Javorka
- Department of Physiology and Biomedical Centre Martin (BioMed Martin), Jessenius Faculty of Medicine, Comenius University, Martin, Slovakia
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10
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Porta A, Elstad M. Editorial: Probing the Cardiac Arm of the Baroreflex and Complementary Branches. Front Neurosci 2020; 13:1422. [PMID: 31998069 PMCID: PMC6967736 DOI: 10.3389/fnins.2019.01422] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 12/16/2019] [Indexed: 11/19/2022] Open
Affiliation(s)
- Alberto Porta
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.,Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy
| | - Maja Elstad
- Division of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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11
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De Maria B, Bari V, Sgoifo A, Carnevali L, Cairo B, Vaini E, Catai AM, de Medeiros Takahashi AC, Dalla Vecchia LA, Porta A. Concomitant Evaluation of Heart Period and QT Interval Variability Spectral Markers to Typify Cardiac Control in Humans and Rats. Front Physiol 2019; 10:1478. [PMID: 31849718 PMCID: PMC6897045 DOI: 10.3389/fphys.2019.01478] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 11/18/2019] [Indexed: 02/04/2023] Open
Abstract
The variability of heart period, measured as the time distance between two consecutive QRS complexes from the electrocardiogram (RR), was exploited to infer cardiac vagal control, while the variability of the duration of the electrical activity of the heart, measured as the time interval from Q-wave onset to T-wave end (QT), was proposed as an indirect index of cardiac sympathetic modulation. This study tests the utility of the concomitant evaluation of RR variability (RRV) and QT variability (QTV) markers in typifying cardiac autonomic control of humans under different experimental conditions and of rat groups featuring documented differences in resting sympatho-vagal balance. We considered: (i) 23 healthy young subjects in resting supine position (REST) undergoing head-up tilt at 45° (T45) and 90° (T90) followed by recovery to the supine position; (ii) 9 Wistar (WI) and 14 wild-type Groningen (WT) rats in unstressed conditions, where the WT animals were classified as non-aggressive (non-AGG, n = 9) and aggressive (AGG, n = 5) according to the resident intruder test. In humans, spectral analysis of RRV and QTV was performed over a single stationary sequence of 250 consecutive values. In rats, spectral analysis was iterated over 10-min recordings with a frame length of 250 beats with 80% overlap and the median of the distribution of the spectral markers was extracted. Over RRV and QTV we computed the power in the low frequency (LF, from 0.04 to 0.15 Hz in humans and from 0.2 to 0.75 Hz in rats) band (LFRR and LFQT) and the power in the high frequency (HF, from 0.15 to 0.5 Hz in humans and from 0.75 to 2.5 Hz in rats) band (HFRR and HFQT). In humans the HFRR power was lower during T90 and higher during recovery compared to REST, while the LFQT power was higher during T90. In rats the HFRR power was lower in WT rats compared to WI rats and the LFQT power was higher in AGG than in non-AGG animals. We concluded that RRV and QTV provide complementary information in describing the functioning of vagal and sympathetic limbs of the autonomic nervous system in humans and rats.
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Affiliation(s)
| | - Vlasta Bari
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy
| | - Andrea Sgoifo
- Stress Physiology Laboratory, Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parma, Italy.,Microbiome Research Hub, University of Parma, Parma, Italy
| | - Luca Carnevali
- Stress Physiology Laboratory, Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parma, Italy.,Microbiome Research Hub, University of Parma, Parma, Italy
| | - Beatrice Cairo
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | - Emanuele Vaini
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy
| | | | | | | | - Alberto Porta
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy.,Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
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Milan-Mattos JC, de Oliveira Francisco C, Ferroli-Fabrício AM, Minatel V, Marcondes ACA, Porta A, Beltrame T, Parizotto NA, Ferraresi C, Bagnato VS, Catai AM. Acute effect of photobiomodulation using light-emitting diodes (LEDs) on baroreflex sensitivity during and after constant loading exercise in patients with type 2 diabetes mellitus. Lasers Med Sci 2019; 35:329-336. [PMID: 31203569 DOI: 10.1007/s10103-019-02815-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 05/23/2019] [Indexed: 10/26/2022]
Abstract
To evaluate the photobiomodulation (PBM) effect on the cardiovascular autonomic control, analyzed by baroreflex sensitivity (sequence method), during constant load exercise and recovery in diabetic men, we evaluated 11 men with type 2 diabetes (DM2) (40-64 years). The constant workload exercise protocol (TECC) was performed on two different days, 14 days apart from each other, to guarantee PBM washout period. After PBM by light-emitting diode (LED) irradiation (150 J or 300 J or placebo), 10 min of rest (REST) was performed. After this period, the volunteer was positioned on a cycloergometer to start the test (1-min rest, 3-min free-load heating, 6-min constant workload-EXERCISE, 6-min free-load cool-down, 1-min rest) followed by a sitting period of 10 min (RECOVERY). The constant workload corresponded to 80%VO2GET (gas exchange threshold) identified by a previous cardiopulmonary exercise test (CPET). PBM was applied in continuous mode, contact technique, bilaterally, on both femoral quadriceps and gastrocnemius muscle groups. The electrocardiogram R-R intervals (BioAmp FE132) and the peripheral pulse pressure signals (Finometer PRO) were collected continuously throughout the protocol. Stable sequences of 256 points were chosen at REST, EXERCISE, and RECOVERY. The baroreflex sensitivity (BRS) was computed in time domain according to the sequence method (αseq). The comparison between therapies (150 J/300 J/placebo) and condition (REST, EXERCISE, and RECOVERY) was performed using the ANOVA two-way repeated measures test. There was no interaction between therapy and conditions during the TECC. There was only the condition effect (p < 0.001), showing that the behavior of αseq was similar regardless of the therapy. Photobiomodulation with 150 J or 300 J applied previously to a moderate-intensity TECC in DM2 was not able to promote cardiovascular autonomic control changes leading to an improvement in BRS.
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Affiliation(s)
- Juliana Cristina Milan-Mattos
- Cardiovascular Physical Therapy Laboratory, Department of Physical Therapy, Federal University of São Carlos, São Carlos, Brazil.
| | - Cristina de Oliveira Francisco
- Cardiovascular Physical Therapy Laboratory, Department of Physical Therapy, Federal University of São Carlos, São Carlos, Brazil
| | | | | | - Ana Carolina Aparecida Marcondes
- Cardiovascular Physical Therapy Laboratory, Department of Physical Therapy, Federal University of São Carlos, São Carlos, Brazil
| | - Alberto Porta
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.,Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy
| | - Thomas Beltrame
- Computing Institute, Campinas State University, Campinas, Brazil
| | - Nivaldo Antônio Parizotto
- Cardiovascular Physical Therapy Laboratory, Department of Physical Therapy, Federal University of São Carlos, São Carlos, Brazil.,Post-Graduation Program in Biotecnology, Araraquara University - UNIARA, Araraquara, Brazil.,Post-Graduation Program in Biomedical Engineering, Universidade Brasil, São Paulo, Brazil
| | - Cleber Ferraresi
- Post-Graduation Program in Biomedical Engineering, Universidade Brasil, São Paulo, Brazil
| | | | - Aparecida Maria Catai
- Cardiovascular Physical Therapy Laboratory, Department of Physical Therapy, Federal University of São Carlos, São Carlos, Brazil
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13
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De Maria B, Bari V, Cairo B, Vaini E, Esler M, Lambert E, Baumert M, Cerutti S, Dalla Vecchia L, Porta A. Characterization of the Asymmetry of the Cardiac and Sympathetic Arms of the Baroreflex From Spontaneous Variability During Incremental Head-Up Tilt. Front Physiol 2019; 10:342. [PMID: 31001137 PMCID: PMC6454064 DOI: 10.3389/fphys.2019.00342] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Accepted: 03/13/2019] [Indexed: 11/13/2022] Open
Abstract
Hysteresis of the baroreflex (BR) is the result of the different BR sensitivity (BRS) when arterial pressure (AP) rises or falls. This phenomenon has been poorly studied and almost exclusively examined by applying pharmacological challenges and static approaches disregarding causal relations. This study inspects the asymmetry of the cardiac BR (cBR) and vascular sympathetic BR (sBR) in physiological closed loop conditions from spontaneous fluctuations of physiological variables, namely heart period (HP) and systolic AP (SAP) leading to the estimation of cardiac BRS (cBRS) and muscle sympathetic nerve activity (MSNA) and diastolic AP (DAP) leading to the estimation of vascular sympathetic BRS (sBRS). The assessment was carried out in 12 young healthy subjects undergoing incremental head-up tilt with table inclination gradually increased from 0 to 60°. Two analytical methods were exploited and compared, namely the sequence (SEQ) and phase-rectified signal averaging (PRSA) methods. SEQ analysis is based on the detection of joint causal schemes representing the HP and MSNA burst rate delayed responses to spontaneous SAP and DAP modifications, respectively. PRSA analysis averages HP and MSNA burst rate patterns after aligning them according to the direction of SAP and DAP changes, respectively. Since cBRSs were similar when SAP went up or down, hysteresis of cBR was not detected. Conversely, hysteresis of sBR was evident with sBRS more negative when DAP was falling than rising. sBR hysteresis was no longer visible during sympathetic activation induced by the orthostatic challenge. These results were obtained via the SEQ method, while the PRSA technique appeared to be less powerful in describing the BR asymmetry due to the strong association between BRS estimates computed over positive and negative AP variations. This study suggests that cBR and sBR provide different information about the BR control, sBR exhibits more relevant non-linear features that are evident even during physiological changes of AP, and the SEQ method can be fruitfully exploited to characterize the BR hysteresis with promising applications to BR branches different from cBR and sBR.
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Affiliation(s)
| | - Vlasta Bari
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy
| | - Beatrice Cairo
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | - Emanuele Vaini
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy
| | - Murray Esler
- Human Neurotransmitters Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia
| | - Elisabeth Lambert
- Human Neurotransmitters Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia.,Faculty of Health, Arts and Design, Iverson Health Innovation Research Institute, Swinburne University of Technology, Hawthorn, VIC, Australia
| | - Mathias Baumert
- School of Electrical and Electronic Engineering, The University of Adelaide, Adelaide, SA, Australia
| | - Sergio Cerutti
- Department of Electronics Information and Bioengineering, Politecnico di Milano, Milan, Italy
| | | | - Alberto Porta
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy.,Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
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14
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de Oliveira Gois M, Porta A, Simões RP, Kunz VC, Driusso P, Hirakawa HS, De Maria B, Catai AM. The additional impact of type 2 diabetes on baroreflex sensitivity of coronary artery disease patients might be undetectable in presence of deterioration of mechanical vascular properties. Med Biol Eng Comput 2019; 57:1405-1415. [PMID: 30843124 DOI: 10.1007/s11517-019-01966-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Accepted: 02/21/2019] [Indexed: 01/14/2023]
Abstract
Both deterioration of the mechanical vascular properties of barosensitive vessels and autonomic derangement lead to modification of baroreflex sensitivity (BRS) in coronary artery disease (CAD) individuals. Type 2 diabetes (T2D) reduces BRS as well even in absence of cardiac autonomic neuropathy. The aim of the study is to clarify whether, assigned the degree of mechanical vascular impairment and without cardiac autonomic neuropathy, the additional autonomic dysfunction imposed in CAD patients by T2D (CAD-T2D) decreases BRS further. We considered CAD (n = 18) and CAD-T2D (n = 19) males featuring similar increases of average carotid intima media thickness (ACIMT) and we compared them to age- and gender-matched healthy (H, n = 19) subjects. BRS was computed from spontaneous beat-to-beat variability of heart period (HP) and systolic arterial pressure (SAP) at supine resting (REST) and during active standing (STAND). BRS was estimated via methods including time domain, spectral, cross-spectral, and model-based techniques. We found that (i) at REST BRS was lower in CAD and CAD-T2D groups than in H subjects but no difference was detected between CAD and CAD-T2D individuals; (ii) STAND induced an additional decrease of BRS visible in all the groups but again BRS estimates of CAD and CAD-T2D patients were alike; (iii) even though with different statistical power, BRS markers reached similar conclusions with the notable exception of the BRS computed via model-based approach that did not detect the BRS decrease during STAND. In presence of a mechanical vascular impairment, indexes estimating BRS from spontaneous HP and SAP fluctuations might be useless to detect the additional derangement of the autonomic control in CAD-T2D without cardiac autonomic neuropathy compared to CAD, thus limiting the applications of cardiovascular variability analysis to typify CAD-T2D individuals. Graphical abstract Graphical representation of the baroreflex sensitivity (BRS) estimated from spontaneous fluctuations of heart period and systolic arterial pressure via transfer function (TF) in low frequency (LF) band (from 0.04 to 0.15 Hz). BRS was reported as a function of the group (i.e., healthy (H), coronary artery disease (CAD) and CAD with type 2 diabetes (CAD-T2D) groups) at REST (black bars) and during STAND (white bars). Values are shown as mean plus standard deviation. The symbol "*" indicates a significant difference between conditions within the same group (i.e., H, CAD, or CAD-T2D) and the symbol "§" indicates a significant difference between groups within the same experimental condition (i.e., REST or STAND). BRS cannot distinguish CAD and CAD-T2D groups both at REST and during STAND, while it is useful to distinguish experimental conditions and separate pathological groups from H subjects.
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Affiliation(s)
| | - Alberto Porta
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy.
| | | | - Vandeni Clarice Kunz
- Adventist University Center of São Paulo, Campus Engenheiro Coelho, São Paulo, Brazil
| | - Patricia Driusso
- Department of Physical Therapy, Federal University of São Carlos, São Carlos, São Paulo, Brazil
| | | | | | - Aparecida Maria Catai
- Department of Physical Therapy, Federal University of São Carlos, São Carlos, São Paulo, Brazil
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15
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Petelczyc M, Bruhn S, Weippert M. Coupling of local muscle deoxygenation and autonomic control depends on exercise intensity-insights from transfer entropy analysis. Physiol Meas 2018; 39:125005. [PMID: 30524086 DOI: 10.1088/1361-6579/aaec9a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE We analyzed the driving component between the periods of adjacent heartbeats (R-R intervals) and vastus lateralis-deoxygenation (%HHb) during incremental cycling. Considering a tight matching of local metabolism with systemic and local perfusion, a coupling between indices of cardiovascular control (R-R variability) and %HHb is suggested. Further, an intensity-dependent coupling between R-R variability and %HHb was hypothesized, because a multitude of feedback and feedforward mechanisms to autonomic cardiovascular control as well as local vasodilating mechanisms are associated with muscle metabolism and thus exercise intensity. APPROACH Ten male triathletes (age: 34 ± 8 years) completed a test, including baseline (BAS, 50 W), a 25 W * min-1 ramp incremental phase until exhaustion and a recovery period (REC, 50 W). R-R intervals, %HHb and respiratory responses were simultaneously recorded. Five corresponding data segments were selected: BAS, before the first ventilatory threshold (preGET), between GET and the respiratory compensation point (preRCP), above RCP (postRCP), and REC. Bivariate transfer entropy (BTE) was applied to determine the signal coupling between R-R and %HHb. MAIN RESULTS During preGET and preRCP, the analysis yielded the dominating direction from %HHb to R-R intervals, while for postRCP the direction was reversed. No significant signal coupling was detectable for the BAS and REC segments. SIGNIFICANCE Assuming that %HHb is related to the metabolic state of the working muscle, BTE results support the role of metaboreceptors in the systemic blood flow regulation at lower exercise intensities, while other mechanisms (e.g. baroreceptor and mechanoreceptor feedback, central command) that modulate cardiovascular control may override this coupling at higher intensities.
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Affiliation(s)
- M Petelczyc
- Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-662, Poland. Authors contributed equally to this manuscript
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Porta A, Bari V, De Maria B, Cairo B, Vaini E, Perseguini NM, Milan-Mattos J, Rehder-Santos P, Minatel V, Takahashi ACM, Catai AM. Comparison between probabilistic and Wiener-Granger causality in assessing modifications of the cardiac baroreflex control with age. Physiol Meas 2018; 39:104004. [PMID: 30207986 DOI: 10.1088/1361-6579/aae0ec] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
BACKGROUND Probabilistic causality (PC) is a framework for checking that the occurrence of a cause raises the probability of the effect by comparing the probability of the effect conditioned and unconditioned to the cause. Even though it is less frequently utilized with respect to the more traditional model-based Wiener-Granger causality (WGC) that is based on the predictability improvement of an effect resulting from the inclusion of the presumed cause in the multivariate linear regression model, PC has the advantage of being model-free. OBJECTIVE The aim of the study is to apply the PC framework to assess the evolution of cardiac baroreflex control with age from spontaneous fluctuations of heart period (HP) and systolic arterial pressure (SAP) and to compare it to the more common WGC approach. APPROACH We studied 100 healthy humans (54 males, age: 21-70 years, 20 subjects for each 10 years bin). HP and SAP were extracted on a beat-to-beat basis from 5 min recordings of electrocardiogram and plethysmographic arterial pressure at rest in supine position (REST) and during active standing (STAND) under spontaneous breathing. The WGC ratio (WGCR) was computed as the log ratio of the prediction error variance of the autoregressive model on HP to that on HP with exogenous SAP. The PC ratio (PCR) was computed as the probability of observing an HP ramp given an associated parallel SAP variation divided by the probability of observing an HP ramp. MAIN RESULTS The WGCR and PCR suggested the gradual impairment of cardiac baroreflex with age, especially during STAND. Moreover, they were significantly associated both at REST and during STAND but the degree of the PCR-WGCR association was weak. SIGNIFICANCE PC can be effectively exploited to assess modification of the cardiovascular control during senescence even though a limited agreement was observed with WGC.
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Affiliation(s)
- Alberto Porta
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy. Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy. Address for correspondence: Università degli Studi di Milano, Dipartimento di Scienze Biomediche per la Salute, IRCCS Policlinico San Donato, Laboratorio di Modellistica di Sistemi Complessi, Via F. Fellini 4, 20097, San Donato Milanese, Milano, Italy
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Porta A, Bari V, De Maria B, Cairo B, Vaini E, Malacarne M, Pagani M, Lucini D. On the Relevance of Computing a Local Version of Sample Entropy in Cardiovascular Control Analysis. IEEE Trans Biomed Eng 2018; 66:623-631. [PMID: 29993481 DOI: 10.1109/tbme.2018.2852713] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Traditional definition of sample entropy (SampEn), here referred to as global SampEn (GSampEn), provides a conditional entropy estimate that blurs the local statistical properties of the time series. We hypothesized that a local version of SampEn (LSampEn) might be more powerful in the presence of determinism than GSampEn. METHODS LSampEn was computed by calculating the probability of the current sample conditioned on each reference pattern and averaging it over all reference patterns. The improved ability of LSampEn compared to GSampEn was demonstrated by simulating deterministic periodic, deterministic chaotic, and linear stochastic dynamics corrupted by additive noise and over real cardiovascular variability series recorded from 16 healthy subjects (max-min age range: 22-58 years) during incremental bicycle ergometer exercise. RESULTS We found that: i) LSampEn is more robust in describing deterministic periodic or nonlinear features in the presence of additive noise than GSampEn, ii) in association with a surrogate approach, LSampEn is more powerful in detecting nonlinear dynamics than GSampEn, iii) LSampEn and GSampEn are equivalent in the presence of stochastic linear dynamics, and iv) only LSampEn can detect the decrease of complexity of heart period variability during bicycle exercise being a likely hallmark of sympathetic activation. CONCLUSION LSampEn preserves the GSampEn capability in characterizing the complexity of short sequences but improves its reliability in the presence of deterministic patterns featuring sharp state transitions and nonlinear dynamics. SIGNIFICANCE Variations of complexity can be measured with a greater statistical power over short series using LSampEn, especially when nonlinear features are present.
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