Search

info:eu-repo/semantics/nonPublished

info:eu-repo/semantics/nonPublished

info:eu-repo/semantics/nonPublished

info:eu-repo/semantics/nonPublished

Aims: To improve telemonitoring strategies in heart failure patients, there is a need for novel non-obtrusive sensors that monitor parameters closely related to intracardiac filling pressures. This proof-of-concept study aims to evaluate the responsiveness of cardiac kinetic energy (KE) measured with the Kinocardiograph (KCG), consisting of a seismocardiographic (SCG) sensor and a ballistocardiographic (BCG) sensor, during treatment of patients with acute decompensated heart failure. Methods and results: Eleven patients with acute decompensated heart failure who were hospitalized for treatment with intravenous diuretics received daily KCG measurements. The KCG measurements were compared with the diameter of the inferior vena cava (IVC) and body weight. Follow-up stopped at discharge, that is, in the recompensated state. Median (interquartile range) weight and IVC diameter decreased significantly after diuretic treatment [weight 74.5 (67.6–98.7) to 73.3 (66.7–95.6) kg, P = 0.003; IVC diameter 2.47 (2.33–2.99) to 1.78 (1.65–2.47) cm, P = 0.03]. In contrast with BCG measurements, significant changes in median KE measured with SCG were observed during the passive filling phase of the diastole [SGG: 0.48 (0.39–0.60) to 0.69 (0.56–0.84), P = 0.026; BCG: 0.68 (0.46–0.73) to 0.68 (0.59–0.82), P = 0.062], the active filling phase of the diastole [SCG: 0.38 (0.30–0.61) to 0.31 (0.09–0.47), P = 0.016; BCG: 0.29 (0.17–0.39) to 0.26 (0.20–0.34), P = 0.248], and the ratio between the passive and active filling phases [SCG: 2.76 (1.68–5.30) to 5.02 (3.13–10.17), P = 0.006; BCG: 5.87 (3.57–7.55) to 5.27 (3.95–9.43), P = 0.790]. The correlations between changes in KE during the passive and active filling phases, using SCG, and changes in weight or IVC were non-significant. Systolic KE did not show significant changes. Conclusion: KE measured with the KCG using SCG is highly responsive to changes in fluid status. Future research is needed to confirm its accuracy in a larger study pop, SCOPUS: ar.j, info:eu-repo/semantics/published

Non-invasive remote detection of cardiac and blood displacements is an important topic in cardiactelemedicine. Here we propose kinocardiography (KCG), a non-invasive technique based onmeasurement of body vibrations produced by myocardial contraction and blood flow through thecardiac chambers and major vessels. KCG is based on ballistocardiography and seismocardiographyand measures 12 degrees-of-freedom (DOF) of body motion. The integral of kinetic energy (iK)and maximum Power (Pmax) obtained from the linear and rotational SCG/BCG signals, was computedover the cardiac cycle, and used as a marker of cardiac mechanical function. We showedthat KCG metrics show high repeatability, can be computed on 50 Hz and 1 kHz SCG/BCG signalsindifferently, that most of the metrics were highly similar when computed on different sensors,and with less than 5% of error when computed on record length longer than 60 s. Finally, weshow that KCG metrics allow detecting dobutamine-induced haemodynamic changes with a highaccuracy and present a major improvement over single axis ballistocardiography or seismocardiography.These results suggest that KCG may be a robust and non-invasive method to monitorcardiac inotropic activity., Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished

AIMS: The kinocardiograph (KCG) is an unobtrusive device, consisting of a chest sensor, which records local thoracic vibrations produced in result of cardiac contraction and ejection of blood into the great vessels [seismocardiography (SCG)], and a lower back sensor, which records micromovements of the body in reaction to blood flowing through the vasculature [ballistocardiography (BCG)]. SCG and BCG signals are translated to the integral of cardiac kinetic energy (iK) and cardiac maximum power (Pmax), which might be promising metrics for future telemonitoring purposes in heart failure (HF). As a first step of validation, this study aimed to determine whether iK and Pmax are responsive to exercise-induced changes in the haemodynamic load of the heart in HF patients.METHODS AND RESULTS: Fifteen patients with stable HF with reduced ejection fraction performed a submaximal exercise protocol. KCG and cardiac ultrasound measurements were obtained both at rest and at submaximal exercise. BCG iK over the cardiac cycle (CC) increased significantly (0.0026 ± 0.0017 to 0.0052 ± 0.0061 mJ.s.; P = 0.01) during exercise, in contrast to a non-significant increase in SCG iK CC. BCG Pmax CC increased significantly (0.92 ± 0.89 to 2.03 ± 1.95 mJ/s; P = 0.02), in contrast to a non-significant increase in SCG Pmax CC. When analysing the systolic phase of the CC, similar patterns were found. Cardiac output (CO) ratio (i.e. CO exercise/CO rest) showed a moderate, significant correlation with BCG Pmax CC ratio (r = +0.65; P = 0.008) and with SCG Pmax CC ratio (r = +0.54; P = 0.04).CONCLUSIONS: iK and Pmax measured with the KCG, preferentially using BCG, are responsive to changes in the haemodynamic load of the heart in HF patients. The combination of the BCG and SCG sensor might be of added value to fully understand changes in haemodynamics and to discriminate between an HF patient and a healthy individual.

info:eu-repo/semantics/published

Introduction: Seismocardiography (SCG) records cardiac and blood-induced motions transmitted to the chest surface as vibratory phenomena. Evidences demonstrate that acute myocardial ischemia (AMI) profoundly affects the SCG signals. Multidimensional SCG records cardiac vibrations in linear and rotational dimensions, and scalar parameters of kinetic energy can be computed. We speculate that AMI and revascularization profoundly modify cardiac kinetic energy as recorded by SCG. Methods: Under general anesthesia, 21 swine underwent 90 min of myocardial ischemia induced by percutaneous sub-occlusion of the proximal left anterior descending (LAD) coronary artery and subsequent revascularization. Invasive hemodynamic parameters were continuously recorded. SCG was recorded during baseline, immediately and 80 min after LAD sub-occlusion, and immediately and 60 min after LAD reperfusion. iK was automatically computed for each cardiac cycle (iK CC ) in linear (iK Lin ) and rotational (iK Rot ) dimensions. iK was calculated as well during systole and diastole (iK Sys and iK Dia ,respectively). Echocardiography was performed at baseline and after revascularization, and the left ventricle ejection fraction (LVEF) along with regional left ventricle (LV) wall abnormalities were evaluated. Results: Upon LAD sub-occlusion, 77% of STEMI and 24% of NSTEMI were observed. Compared to baseline, troponins increased from 13.0 (6.5; 21.3) ng/dl to 170.5 (102.5; 475.0) ng/dl, and LVEF dropped from 65.0 ± 0.0 to 30.6 ± 5.7% at the end of revascularization (both p < 0.0001). Regional LV wall abnormalities were observed as follows: anterior MI, 17.6% (three out of 17); septal MI, 5.8% (one out of 17); antero-septal MI, 47.1% (eight out of 17); and infero-septal MI, 29.4% (five out of 17). In the linear dimension, i K L i n C C ,i K L i n S y s ,and i K L i n D i a dropped by 43, 52, and 53%, respectively (p < 0.0001, p < 0.0001, and p = 0.03, respectively) from baseline to the end of reperfusion, SCOPUS: ar.j, info:eu-repo/semantics/published

Recent years have witnessed an upsurge in the usage of ballistocardiography (BCG) and seismocardiography (SCG) to record myocardial function both in normal and pathological populations. Kinocardiography (KCG) combines these techniques by measuring 12 degrees-of-freedom of body motion produced by myocardial contraction and blood flow through the cardiac chambers and major vessels. The integral of kinetic energy (iK) obtained from the linear and rotational SCG/BCG signals, and automatically computed over the cardiac cycle, is used as a marker of cardiac mechanical function. The present work systematically evaluated the test–retest (TRT) reliability of KCG iK derived from BCG/SCG signals in the short term (<15 min) and long term (3–6 h) on 60 healthy volunteers. Additionally, we investigated the difference of repeatability with different body positions. First, we found high short-term TRT reliability for KCG metrics derived from SCG and BCG recordings. Exceptions to this finding were limited to metrics computed in left lateral decubitus position where the TRT reliability was moderate-to-high. Second, we found low-to-moderate long-term TRT reliability for KCG metrics as expected and confirmed by blood pressure measurements. In summary, KCG parameters derived from BCG/SCG signals show high repeatability and should be further investigated to confirm their use for cardiac condition longitudinal monitoring., SCOPUS: ar.j, info:eu-repo/semantics/published

Ballistocardiography (BCG) and seismocardiography (SCG) assess vibrations produced by cardiac contraction and blood flow, respectively, through micro-accelerometers and micro-gyroscopes. BCG and SCG kinetic energies (KE) and their temporal integrals (K) during a single heartbeat are computed in linear and rotational dimensions. Our aim was to test the hypothesis that K from BCG and SCG are related to sympathetic activation during maximal voluntary end-expiratory apnea. Multiunit muscle sympathetic nerve traffic [burst frequency (BF), total muscular sympathetic nerve activity (tMSNA)] was measured by microneurography during normal breathing and apnea ( = 28, healthy men). K of BCG and SCG were simultaneously recorded in the linear and rotational dimension, along with oxygen saturation ([Formula: see text]) and systolic blood pressure (SBP). The mean duration of apneas was 25.4 ± 9.4 s. SBP, BF, and tMSNA increased during the apnea compared with baseline ( = 0.01, = 0.002,and = 0.001, respectively), whereas [Formula: see text] decreased ( = 0.02). At the end of the apnea compared with normal breathing, changes in K computed from BCG were related to changes of tMSNA and BF only in the linear dimension ( = 0.85, < 0.0001; and = 0.72, = 0.002, respectively), whereas changes in linear K of SCG were related only to changes of tMSNA ( = 0.62, = 0.01). We conclude that maximal end expiratory apnea increases cardiac kinetic energy computed from BCG and SCG, along with sympathetic activity. The novelty of the present investigation is that linear K of BCG is directly and more strongly related to the rise in sympathetic activity than the SCG, mainly at the end of a sustained apnea, likely because the BCG is more affected by the sympathetic and hemodynamic effects of breathing cessation. BCG and SCG may prove useful to assess sympathetic nerve changes in patients with sleep disturbances. NEW & NOTEWORTHY Ballistocardiography (BCG) and seismocardiography (SCG) assess vibrations pr

Ballistocardiography (BCG) and seismocardiography (SCG) assess vibrations produced by cardiac contraction and blood flow, respectively, through micro-accelerometers and micro-gyroscopes. BCG and SCG kinetic energies (KE) and their temporal integrals (iK) during a single heartbeat are computed in linear and rotational dimensions. Our aim was to test the hypothesis that iK from BCG and SCG are related to sympathetic activation during maximal voluntary end-expiratory apnea. Multiunit muscle sympathetic nerve traffic [burst frequency (BF), total muscular sympathetic nerve activity (tMSNA)] was measured by microneurography during normal breathing and apnea (n = 28, healthy men). iK of BCG and SCG were simultaneously recorded in the linear and rotational dimension, along with oxygen saturation (SatO2 ) and systolic blood pressure (SBP). The mean duration of apneas was 25.4 9.4 s. SBP, BF, and tMSNA increased during the apnea compared with baseline (P = 0.01, P = 0.002, and P = 0.001, respectively), whereas SatO2 decreased (P = 0.02). At the end of the apnea compared with normal breathing, changes in iK computed from BCG were related to changes of tMSNA and BF only in the linear dimension (r=0.85, P < 0.0001; and r = 0.72, P = 0.002, respectively), whereas changes in linear iK of SCG were related only to changes of tMSNA (r = 0.62, P = 0.01). We conclude that maximal end expiratory apnea increases cardiac kinetic energy computed from BCG and SCG, along with sympathetic activity. The novelty of the present investigation is that linear iK of BCG is directly and more strongly related to the rise in sympathetic activity than the SCG, mainly at the end of a sustained apnea, likely because the BCG is more affected by the sympathetic and hemodynamic effects of breathing cessation. BCG and SCG may prove useful to assess sympathetic nerve changes in patients with sleep disturbances. NEW & NOTEWORTHY Ballistocardiography (BCG) and seismocardiography (SCG) assess vibrations produced, SCOPUS: ar.j, info:eu-repo/semantics/published

To investigate if modern seismocardiography (SCG) and ballistocardiography (BCG) are useful in the detection of hemodynamic changes occurring during simulated obstructive apneic events., info:eu-repo/semantics/published

Non-invasive remote detection of cardiac and blood displacements is an important topic in cardiac telemedicine. Here we propose kino-cardiography (KCG), a non-invasive technique based on measurement of body vibrations produced by myocardial contraction and blood flow through the cardiac chambers and major vessels. KCG is based on ballistocardiography and measures 12 degrees-of-freedom (DOF) of body motion. We tested the hypothesis that KCG reliably assesses dobutamine-induced haemodynamic changes in healthy subjects. Using a randomized double-blinded placebo-controlled crossover study design, dobutamine and placebo were infused to 34 volunteers (25 ± 2 years, BMI 22 ± 2 kg/m², 18 females). Baseline recordings were followed by 3 sessions of increasing doses of dobutamine (5, 10, 20 μg/kg.min) or saline solution. During each session, stroke volume (SV) and cardiac output (CO) were determined by echocardiography and followed by a 90 s KCG recording. Measured linear accelerations and angular velocities were used to compute total Kinetic energy (iK) and power (Pmax). KCG sorted dobutamine infusion vs. placebo with 96.9% accuracy. Increases in SV and CO were correlated to iK (r = +0.71 and r = +0.8, respectively, p < 0.0001). Kino-cardiography, with 12-DOF, allows detecting dobutamine-induced haemodynamic changes with a high accuracy and present a major improvement over single axis ballistocardiography or seismocardiography., info:eu-repo/semantics/published

Objective: To assess if micro-accelerometers and gyroscopes may provide useful information for the detection of breathing disturbances in further studies. Approach: Forty-three healthy volunteers performed a 10 s end-expiratory breath-hold, while ballistocardiograph (BCG) and seismocardiograph (SCG) determined changes in kinetic energy and its integral over time (iK, J • s). BCG measures overall body accelerations in response to blood mass ejection into the main vasculature at each cardiac cycle, while SCG records local chest wall vibrations generated beat-by-beat by myocardial activity. This minimally intrusive technology assesses linear accelerations and angular velocities in 12 degrees of freedom to calculate iK during the whole cardiac cycle. iK produced during systole and diastole were also computed. Main results: The iK during normal breathing was 87.1 [63.3; 132.8] µJ • s for the SCG and 4.5 [3.3; 6.2] µJ • s for the BCG. Both increased to 107.1 [69.0; 162.0] µJ • s and 6.1 [4.4; 9.0] µJ • s, respectively, during breath-holding (p = 0.003 and p < 0.0001, respectively). The iK of the SCG further increased during spontaneous respiration following apnea (from 107.1 [69.0; 162.0] µJ • s to 160.0 [96.3; 207.3] µJ • s, p < 0.0001). The ratio between the iK of diastole and systole increased from 0.35 [0.24; 0.45] during apnea to 0.49 [0.31; 0.80] (p < 0.0001) during the restoration of respiration. Significance: A brief voluntary apnea generates large and distinct increases in SCG and BCG waveforms. iK monitoring during sleep may prove useful for the detection of respiratory disturbances. ClinicalTrials.gov number: NCT03760159, SCOPUS: ar.j, info:eu-repo/semantics/published

Recent studies have demonstrated the possibility to acquire the heartbeat induced vibrations resembling the seismocardiogram (SCG) by the mobile phone accelerometer (m-SCG). As most of ECG-free beat detection algorithms are based on processing one m-SCG component only (e.g. head-to-foot), our aim was to propose an alternative and robust method to extract beat-to-beat systolic complex (SC) from three-axial m-SCG and test its occurrence compared to R peak of ECG. Eleven male subjects (mean age 22±3) were recruited and m-SCG signal (50 Hz) was acquired for 5 minutes by a smartphone positioned on the chest. Newtonian equations of kinematics and continuous wavelet transform were applied to the m-SCG signal to detect beat-by-beat SC occurrence. Data from one subject were discarded due to low quality signal (feasibility 91%). High values of sensitivity (0.995), positive predictive value (0.974) and accuracy (0.96) were obtained. The explored heart rate range (45-101 bpm) was quite wide and acceptable limits of agreement (±1 - ±6 bpm) were achieved., SCOPUS: cp.p, info:eu-repo/semantics/published

Aims. Prolonged immobilization generates cardiac deconditioning, a possible risk factor: efficient countermeasures (CM) are needed to prevent it. We aimed at assessing the effectiveness of high-intensity jump training CM on aortic and mitral flow by Phase-Contrast (PC) MRI during 60 days head-down (-6°) bed-rest (BR). Methods. 23 males (29±6 y, 181±6 cm, 77±7 kg) were enrolled at:envihab research facility in Cologne as part of the European Space Agency BR studies. Participants were randomly allocated to the jump training (JUMP, n = 12) or the control (CTRL, n = 11) groups. Training consisted of 4x10 countermovement jumps and 2x10 hops in a horizontal sledge jump system, with 5-6 sessions/week. PC-MRI images (3T Biograph mMR, Siemens) with interleaved three-directional velocity encoding (VENC: x and y: 80 cm/s; z: 150 cm/s) were obtained (spatial resolution 1.4 x 1.4 mm 2) at the level of the aortic root, and of the mitral plane, before (BCD-4), after 21d (HDT21) and 58d (HDT58), and on the fifth day after BR conclusion (R+4). Velocity images were analysed to compute among others: cardiac output (CO), stroke volume (SV), max blood flow rate (Qpeak), systolic and heart beat duration (RR), rapid filling (Ewave) and early filling peak flow rate (Ef). Results. In CTRL, compared to BCD-4, at HDT58 a significant RR (14%) and systolic (10%) shortening, with a decrease in SV (22%), Qpeak (12%), Ewave (26%), Ef (26%) were observed. In CM, only RR was shortened (8%), together with a decrease in SV (12%), Qpeak (7.5%), Ewave (11%), Ef (15%). Interestingly, at R+4, compared to BCD-4, RR was still decreased by 10% in CTRL, while Ef increased by 18% and by 15%, respectively in CTRL and CM, where also CO (+19%) and SV (+8%) were increased. Conclusions. In this first study addressing aortic and mitral flow using PC-MRI during BR, cardiac deconditioning affected both flows. The applied CM was effective in partially opposing this phenomenon, inducing reduced changes at HDT58., SCOPUS: cp.p, info:eu-repo/semantics/published

info:eu-repo/semantics/published

info:eu-repo/semantics/published

Objective: The aim of this work was to evaluate the potential changes in the ballistocardiogram (BCG) signal induced by different respiratory patterns and posture, by using the dynamic time warping (DTW) technique. Approach: BCG signals were recorded in a group of 20 healthy volunteers, simultaneously with an electrocardiogram (ECG). Two recordings, one in a supine (SUP) and one in a standing (ST) position, including spontaneous breathing, two 1 min apneas (at full and empty-lungs, respectively) and 30 s of Valsalva, were analyzed. A warped averaged waveform was computed for each phase, from which amplitude and temporal parameters were extracted to characterize each condition. Main results: Variations were found in both amplitude and duration of BCG-derived parameters among manoeuvres, especially when compared to spontaneous breathing, suggesting a complex interaction between intra-thoracic pressure changes acting on venous return, together with the autonomic nervous system modulation on heart rate. The effect of a hydrostatic pressure gradient elicited by postural conditions was also evident. Significance: Posture and respiratory manoeuvres affect the BCG signal in different ways, probably as a result of changes induced in preload and afterload. This supports the need to define separate normality ranges for each posture and/or breathing conditions, as well as the importance of applying specific manoeuvres to highlight any pathological response in the computed BCG parameters., SCOPUS: ar.j, info:eu-repo/semantics/published

info:eu-repo/semantics/inPress

The aim of this work was to test if the smartphone's embedded triaxial accelerometer can be used to extract respiratory frequency information from the chest movements during a controlled breathing protocol. Respiratory signals from 10 young volunteers were recorded simultaneously, by two smartphones (iPhone 4s and 6s; sampling frequency ∼100 Hz), positioned one on the sternum and one on the belly, while in supine posture. At the same time, a belt transducer was used to acquire the reference respiratory signal. A controlled breathing protocol, consisting of four consecutive phases of 12 respiratory cycles each (respiratory frequencies at 0.25, 0.17, 0.125 and 0.1 Hz), was imposed through the visualization of a moving bar on a display. After low-pass filtering (fc=0.5 Hz), the respiratory signal was obtained from both smartphones, and respiratory frequency derived for each phase. Compared to the belt transducer, the resulting error was lower than 2% for each imposed respiratory frequency, for both smartphones' positions, with better results obtained for the smartphone positioned above the belly., SCOPUS: cp.p, info:eu-repo/semantics/published

info:eu-repo/semantics/nonPublished

info:eu-repo/semantics/published

Mobile phones offer the possibility to monitor and track health parameters. Our aim was to test the feasibility and accuracy of measuring beat-to-beat heart rate using smartphone accelerometers by recording the vibrations generated by the heart during its function and transmitted to the chest wall, i.e. the so-called seismocardiographic signal (SCG). Methods: 9 healthy male volunteers were studied in supine (SUP) and in standing (ST) posture. A smartphone (iPhone6, Apple) was positioned on the thorax (POS1) to acquire SCG signal. While supine, a second smartphone was positioned on the navel (POS2). The SCG signal was recorded for 3 minutes during spontaneous respiration, synchronous with 3-leads ECG. Using a fully automated algorithm based on amplitude thresholding after rectification, the characteristic peak of the SCG signal (IVC) was detected and used to compute beat-to-beat heart duration, to be compared with the corresponding RR intervals extracted from the ECG. Results: A 100% feasibility of the approach resulted for POS1 in SUP, while 89% in POS2, and 78% for POS1 in ST. In supine, for each smartphones' position, the automated algorithm correctly identified the cardiac beats with >98% accuracy. Linear correlation (r2) with RR was very high (>0.98) in each posture and position, with no bias and narrow limits of agreement. Conclusions: The obtained results proved the feasibility of the proposed approach and the robustness of the applied algorithm in measuring the beat-to-beat heart rate from smartphone-derived SCG, with high accuracy compared to conventional ECG-derived measure., SCOPUS: cp.p, info:eu-repo/semantics/published

Our aim was to assess the effects of 21-days head-down (-6 degrees) bed-rest (BR) and effectiveness of sledge jump countermeasure (CM), on aortic flow and morphology by Phase Contrast (PC) MRI. Male subjects were enrolled at :envihub (DLR, Germany) in control (CTRL, N=12) or countermeasure (CM, N=12) groups. PC-MRI images were obtained before and after 21-days of BR, and analyzed with custom software. Semi-automated region growing and thresholding were applied to segment the aortic lumen, and to compute parameters from velocity images: area lumen (AL), flow velocity, stroke volume (SV), flow rate (Qpeak), time-to-peak flow, systolic duration and heart beat duration (RR). After 21 days, in CTRL significant decreases in SV (14%), Qpeak (5%) and AL (4%) were observed compared to baseline values. Conversely, for CM no changes were observed in these parameters, but only in RR (-8%). Cardiac adaptation to deconditioning due to immobilization resulted in a reduction of SV and Qpeak that might have induced a remodeling process in the ascending aorta, by shrinking of its lumen. The applied CM seemed to counteract at least partially these effects., SCOPUS: cp.p, info:eu-repo/semantics/published

Purpose: High G tolerance is based on the capacity to maintain a sufficient level of arterial pressure (AP) during G load; therefore, we hypothesized that subjects with high G tolerance (H group) would have stronger arterial baroreflex responses compared to subjects with low G tolerance (L group). The carotid baroreflex was evaluated using the neck pressure method (NP), which assesses open-loop responses. Methods: The carotid baroreflex was tested in 16 subjects, n = 8 in the H and L group, respectively, in the supine and upright posture. Heart rate and AP were measured. Results: There were no differences between groups in the maximum slopes of the carotid baroreflex curves. However, the H group had a larger systolic and mean AP (SAP, MAP) increase to the initial hypotensive stimuli of the NP sequence in the upright position compared to the L group, 7.5 ± 6.6 vs 2.0 ± 2.4 and 4.1 ± 3.4 vs 1.1 ± 1.1 mmHg for SAP and MAP, respectively. Furthermore, the L group exhibited an increased latency between stimuli and response in AP in the upright compared to supine position, 4.1 ± 1.0 vs 3.1 ± 0.9 and 4.7 ± 1.1 vs 3.6 ± 0.9 s, for SAP and MAP. No differences in chronotropic responses were observed between the groups. Conclusions: It is concluded that the capacity for reflexive vasoconstriction and maintained speed of the vascular baroreflex during orthostatic stress are coupled to a higher relaxed GOR tolerance., SCOPUS: ar.j, info:eu-repo/semantics/published

Ballistocardiography is recognized as a reliable method for non-invasive assessment of cardiovascular functions. In this work, a wavelet approach was used on the y-axis ballistocardiogram (BCG) to evaluate the respiratory sinus arrhythmia (RSA) phenomenon using a new parameter: the ballistocardiogram amplitude modulation induced by respiration (BAMR). Eamax, local maximum energy of BCGy, was quantified for each cardiac cycle. Then a time series of Eamax was created and analyzed using continuous wavelet transform to provide BAMR values. The ECG was used to compute the RSA amplitude as reference. Data were collected on four subjects participating to an imposed controlled breathing protocol with four different breathing sequences. RSA amplitudes and BAMR present significant changes (p < 0.05) for low breathing rate (0.10 Hz) compared to high breathing rate (0.25 Hz) and a within-subject correlation was observed. This study suggests that BAMR could be used as a relevant alternative to RSA amplitude for HRV investigation., SCOPUS: cp.p, info:eu-repo/semantics/published