[Show abstract][Hide abstract] ABSTRACT: Linear measures of heart rate variability (HRV) during ECG stress test has been widely questioned due to the high signal non-stationary. Such limitations can be overcome by nonlinear measures of HRV based on typical properties of chaotic systems and deterministic fractal. Very few paper addressed such issue and aim of the paper is to describe fractal behavior of HRV during exercise. A fractal analysis by Higuchi's algorithm (FD) has been performed on 26 cardiac patients during resting, stress, early and late recovery phases of ECG stress test. Results showed a significant FD increasing values from resting to stress phase that was not recovered at all immediately after the exercise, and it was slightly recovered both during early and late recovery phase. The performance of fractal analysis of HRV during and after high intensity exercise suggests that it could be a useful index assessing relevant information about underlying physiological recovery.
2014 8th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO); 05/2014
[Show abstract][Hide abstract] ABSTRACT: Arm reaching movements (ARM) are mainly used in rehabilitative settings, as robot mediated therapies, virtual reality and motion capture systems in exergaming. ARM typical consist of gaussian-like bell shaped velocity profile. No previous paper addressed in details their relationships with amplitude and speed of the movement and aim of the paper is to study existing correlations between quantitative kinematics indexes (KI) and to describe their relationships with the amplitude and the velocity of the movement in normal subjects. We studied about one thousands of horizontal and vertical ARM of 10 normal subjects at four amplitude's values (15-20-25- 30°) and at three different target velocity (20-30- 40°/s), quantitatively evaluated by symmetry, skewness, kurtosis and smoothness indexes. KI showed extremely low correlations to each other, clearly describing different ARM features, higher correlations with the velocity than with the amplitude of the movement, and in vertical antigravitary rather than horizontal ARM. Among all KI, smoothness showed the higher correlations' values, following an exponential growth relationship both with velocity and amplitude in horizontal and vertical ARM.
Medical Measurements and Applications Proceedings (MeMeA), 2013 IEEE International Symposium on; 01/2013
[Show abstract][Hide abstract] ABSTRACT: The use of electrocardiogram as biometric has raised attention in the last decade and a wide variety of ECG features were explored to verify the feasibility of such a signal. In this work the authors aim to describe a simple template based approach to the electrocardiographic biometric identification using the morphology of individual's heartbeat. The developed algorithm was tested on different recordings made available in the Physionet public database Fantasia: two different sets of heartbeats were extracted from individual recordings one was used for the template building while the second for the tests. The performances of the algorithm are encouraging with a true acceptance rate of 99.4%, however, the procedure needs to be tested on different recordings of the same individual, or during the course of a whole day or physical activity.
Medical Measurements and Applications Proceedings (MeMeA), 2013 IEEE International Symposium on; 01/2013
[Show abstract][Hide abstract] ABSTRACT: Although symbolic dynamics analysis (SDA) has been proposed for encoding words of different length and symbols, the resulting rapidly growing number of patterns has limited its clinical use. Aim of this study is to propose new SDA indices tested on a clinical data-set. We studied 40 ECG Holter of normal (NR), post-MI (MI), heart failure (HF) and transplanted (TR) subjects. RR differences were encoded into 5 symbols, deriving 3, 5 and 7 length words classified by a dominance's criterion in pattern words with a predominant vagal content (V), decelerating content (D), accelerating content (A), sympathetic content (S) and without variability content (0). Their distributions were then quantified by Kurtosis an Chi-square indexes. Results showed an optimum word-length of 3, where both Kurtosis (2.2±0.6; 2.2±0.9; 3.1±0.9; 4.0±0.4) and Chi-square (7±5; 8±5; 26±17; 106±42, respectively for N, MI, HF and TR) showed very significant p
Computing in Cardiology Conference (CinC), 2013; 01/2013
[Show abstract][Hide abstract] ABSTRACT: Functional recovery of limb mobility of patients with spinal or cerebral injuries can take great advantage of the basic role played by sensorial and proprioceptive stimulations. On this base the Institute of Biomedical Problems of the Russian Academy of Sciences have recently developed the “Regent Suit” (RS), an experimental medical device derived from a suits worn by astronauts for therapeutical purposes during space flights. Although preliminary studies describe rehabilitation outcome of the RS in stroke, EMG changes induced by the suit are not known. Aim of the paper is to describe the effects of RS on lower limb EMG patterns on normal subjects. We studied 30 EMG gait analysis of 5 normal subjects without and with RS. Timing of maximum muscle effort over the gait cycle has been detected by the dominant peak phase of the Gaussian decomposition of the EMG envelope. Results showed a significant anticipatory effect on Soleus and Vastus Lateralis and a delay on the Tibialis Anterior and Semitendinosus due to RS elastic force recall facilitating the agonist muscle activation step. Comprehension of these EMG patterns modifications is at the base of a correct clinical use of the device, for both valid rehabilitative protocols and quantitative outcome evaluation.
Medical Measurements and Applications Proceedings (MeMeA), 2013 IEEE International Symposium on; 01/2013
[Show abstract][Hide abstract] ABSTRACT: Variations in kinematic performances and muscle activations, underlying improvements in muscle function and strength, in response to upper arm training of patients with congenital or acquired brain injuries, are still poorly understood. One of the most interesting features of a robot-mediated therapy is the ability to quantify the performance of the rehabilitation tasks proposed to the patient. Although the shoulder is the most complex joint in the body, both for the range of freedom of movements and for the muscular-tendon structure, not so many commercial or research devices have been proposed to study its movements and no study have proposed a standardized, quantitative kinematic and electromyographic assessment. This study aimed to develop a quantitative assessment of kinematics and electromyographic pattern of the arm's muscles involved in reaching robot-assisted movements by means of indices effectively describing the main pattern features in ten normal subjects. Each subject underwent a specific eight sequences motor task protocol. The system automatically classify each movement detecting its start/end times, extract main kinematic indexes plotting activation and deactivation graphs related to eight emg channels. Results showed that particularly movement smoothness indexes and timing of emg patterns may provide an effective upper arm reaching movement assessment.
Biomedical Robotics and Biomechatronics (BioRob), 2012 4th IEEE RAS & EMBS International Conference on; 01/2012
[Show abstract][Hide abstract] ABSTRACT: Fetal heart rate variability is surely one of the most important parameters to monitor fetal wellbeing. Linear studies, widely employed to study fetal heart variability and its correlations with the development of the autonomous nervous system, have shown some limitations in highlight dynamics potentially relevant. During the last decades, therefore, nonlinear analysis methods have gained a growing interest to analyze the chaotic nature of cardiac activity. Techniques investigating nonlinear dynamics have been already successfully employed in adults, to analyze different physiological and pathological states. Concerning fetal monitoring, instead, a smaller number of papers is available in the literature; even if symbolic dynamics was recently employed to quantify fetal heart rate regularity, demonstrating that the use of this technique may lead to a better and more differentiated understanding of normal fetal physiological development. In this work, we applied the symbolic dynamics to analyze fetal heart rate variability in healthy fetuses at the end of a physiological pregnancy. Our results confirmed the potentiality of the technique to highlight differences between signals characterized by more or less variability.
Studies in health technology and informatics 01/2012; 180:123-7.
[Show abstract][Hide abstract] ABSTRACT: Cardiovascular oscillations following spontaneous ventricular premature complexes (VPC) are described by the so-called heart rate turbulence (HRT) onset (TO) and slope (TS). Since HRT is a marker of baroreflex sensitivity, it can be hypothesized to be affected by the preceding VPC sympatovagal balance (pHF). The aim of this study is to investigate the relationship between HRT parameters and pHF in heart failure (HF) patients. We studied 75 24h ECG Holter recording of HF patients (62±9 years) performing a Spearman correlation analysis between TO, TS and pHF values. According to risk stratification standards, each post-VPC response was classified in 0-normal type or 1-abnormal category. Results showed a 53%, 27%,5%,6% of post-VPC respectively 0, 1a, 1b, 2-category, and a remaining 9% unclassified T0=0 values. pHF showed a moderate to good significant (p
[Show abstract][Hide abstract] ABSTRACT: Visually-impaired people can develop several unhealthy behaviors, including the lack of physical activity or sports, due to the incomplete maturity in the control of their body in the space. This research focuses on the creation of an "exergame" - a videogame especially designed to stimulate physical exercise - that, through voice commands, allows the visually impaired users to practice physical activity and train their abilities. This tool has been developed starting from an existing dance-game, by generating some appropriate interfaces that also involve the sensory channel of sight. Our research aims to study the effects related to this exergame on the motor control mechanism in a blind children's group, aged between 8 and 13 years: it focuses also on the joint use of movement analysis systems and of videogames in order to stimulate the physical activity in these subjects.
Studies in health technology and informatics 01/2012; 180:1212-4.
[Show abstract][Hide abstract] ABSTRACT: Robot-mediated therapy has been a very dynamic area of research in recent years. It promises improvement in sensorimotor as well as cognitive processes and has several advantages, among them the most important is perhaps the possibility to quantify the performances of the rehabilitation task proposed to the patient. Robotics devices are in fact capable to guide or perturb movements of a patient's limb and can record mechanical quantities such as position, velocity and forces applied. The kinematics quantitative assessments allow to estimate patient's progress, whilst the clinical traditional scales permit only quantitative evaluations. Different systems for robot-aided neurorehabilitation are currently available for upper limb rehabilitation. However, none study indicated a standardized quantitative kinetic evaluation of robot assisted upper arm free reaching three-dimensional movements. In this paper a quantitative kinematic assessment of robot assisted upper arm free reaching movements is proposed. Advised indexes can be useful for describing normal patterns and for implementing and testing rehabilitative strategies patients oriented.
Medical Measurements and Applications Proceedings (MeMeA), 2011 IEEE International Workshop on; 07/2011
[Show abstract][Hide abstract] ABSTRACT: In this paper we describe an Italian experience of fetal home monitor, organized using a portable phonocardiography system (product by Pentavox, Hungary), and the method utilized to evaluate its effectiveness in providing quality services and patient satisfaction. Patient satisfaction is an important dimension in the evaluation of quality care delivery. We used phonocardiography technique in our experience of fetal home monitoring as it is non invasive and passive in nature, low-cost and easy to use. A lightweight portable phonocardiograph (Fetaphon-home) was assigned to six selected patients, without effective pregnancy risk to monitor fetal heartbeat, uterine contractions and fetal movements at home or wherever they need it. The selected patients were instructed by trained personnel in the use of the monitoring device. Patients were asked to perform the recording two times a week and to transmit 20-min signal to the reference centre. The home monitoring sessions were performed in addition to the routine surveillance at a gynecologist's office; thus, the home monitoring did not replace clinic visits. The women were requested to fill a satisfaction questionnaire in order to evaluate their quality of life and anxiety state. Preliminary results have shown that home fetal surveillance appreciably reduces the need of travel for patients and consequently their stress. Furthermore, our results suggest that, after a short training, pregnant women are able to record and transmit long traces without troubles. Use of telemedicine system was generally well accepted by pregnant women since it increased the possibility of fetal long-term home surveillance which in turn could increase the efficiency of the service offered to them.
Studies in health technology and informatics 01/2010; 155:176-81.
[Show abstract][Hide abstract] ABSTRACT: Cardiovascular oscillations following spontaneous ventricular premature complexes (VPC) are characterized by a short-term heart rate fluctuation known as heart rate turbulence (HRT) described by the so-called turbulence onset (TO) and slope (TS). Despite a recent written consensus on the standard of HRT measurement, reproducibility data are lacking. Aim of the paper was a reproducibility study of HRT indexes in heart failure patients (HF). Eleven HF patients underwent two 24h ECG Holter recordings, spaced 7 ± 5 days. A paired t test was used to assess the clinical stability of patients during the study period and the number of PVC in Holter recordings' couples. Both TO and TS indexes were calculated for each isolated VPC, and due to their skewed distribution, reproducibility of median and mean TO and TS was studied by Bland-Altman technique. Results showed that median HRT indexes might be preferred to commonly suggested mean values and that, although TO showed lower bias value than TS, TS can be considered much more reproducible than TO, comparing limits of agreements with normal values. This preliminary results suggest the use of medians instead of mean HRT indexes values and a reliability of the turbulence slope greater than the turbulence onset index.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2010; 2010:2573-6.
[Show abstract][Hide abstract] ABSTRACT: We propose an approach based on time reversibility analysis to characterize the cardiovascular regulation and its nonlinearities as derived from 24 hours Holter recordings of heart period variability in a healthy population (n=12, age: median=43 years, range=34-55 years) and in a pathological group of age-matched chronic heart failure (CHF) patients (n=13, primarily in NYHA class II, age: median=37 years, range=33-56 years, ejection fraction: median=25%, range=13-30%). Two indices capable of detecting nonlinear irreversible dynamics according to different strategies of phase-space reconstruction (i.e. a fixed two-dimensional phase-space reconstruction and an optimal selection of the embedding dimension, respectively) are tested and compared with a more traditional nonlinear index based on local nonlinear prediction. Results showed that nonlinear dynamics owing to time irreversibility at short time scales are significantly present during daytime in healthy subjects, more frequently present in the CHF population and less frequently during night-time in both groups, thus suggesting their link with a dominant sympathetic regulation and/or with a vagal withdrawal. On the contrary, nonlinear dynamics owing to time irreversibility at longer, dominant time scales were insignificantly present in both groups. During daytime in the healthy population, irreversibility was mostly due to the presence of asymmetric patterns characterized by bradycardic runs shorter than tachycardic ones. Nonlinear dynamics produced by mechanisms different from those inducing temporal irreversibility were significantly detectable in both groups and more frequently during night-time. The present study proposes a method to distinguish different types of nonlinearities and assess their contribution over different temporal scales. Results confirm the usefulness of this method even when applied in uncontrolled experimental conditions such as those during 24 hours Holter recordings.
Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 05/2009; 367(1892):1359-75. · 2.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We studied 54 patients with hypoxemic chronic obstructive pulmonary disease (COPD). The Mini Mental State Examination and the Mental Deterioration Battery were used for neuropsychological assessment. Heart rate variability (HRV) was assessed based on 24-h Holter ECG recording. Mann-Whitney test was used to compare HRV parameters of patients performing normally or abnormally on individual neuropsychological tasks. Spearman's rho was used to investigate the correlations between HRV parameters and neuropsychological scores, indexes of health status or COPD severity. Patients with defective performance at copying drawings with landmarks (CDL) test (N = 23) had lower very low frequency (VLF) power with respect to patients with normal performance (N = 31) (24 h: median 213; interquartile range 120-282 vs. 309; 188-431 ms2, p = 0.043; daytime: 202; 111-292 vs. 342; 194-397 ms2, p = 0.039). The CDL score correlated with the VLF power (24 h: rho = 0.27, p = 0.049; daytime: rho = 0.30, p = 0.028), and the normalized low frequency/high frequency (LF/HF) ratio (24 h: rho = 0.27, p = 0.05; daytime: rho = 0.33, p = 0.015). Sympathetic modulation decreased for increasing severity of COPD. In conclusion, drawing impairment correlates with depressed sympathetic modulation in patients with COPD, and both might be indexes of COPD severity.
Brain and Cognition 04/2009; 70(1):163-70. · 2.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Non-linear parameters obtained from heart rate variability (HRV) analysis has recently been recognized to provide valuable information for physiological interpretation of heart rate fluctuation. Among the numerous non-linear parameters related to the fractal behaviour of the HRV signal, two classes have gained wide interest in the last years: the beta exponent based on the 1/f-like relationship, starting from the spectral power, and that based on fractal dimension. In order to evaluate the relationship between lesion's severity and fractal behaviour, 20 first-ever stroke subjects and 10 healthy subjects were studied. Patients were divided in two groups according to single or multiple medium cerebral artery lesions. All subjects underwent 24-hour Holter recording analysed by fractal and 1/f-like techniques. Differently from methods usually used in literature to evaluate the fractal dimension (FD), in this work the FD was extracted by using the Higuchi's algorithm that permits to calculate the parameter directly from the HRV sequences in the time domain. Results show that fractal analysis contains relevant information related to different HRV dynamics that permits to separate normal subjects from stroke patients. FD is also able to distinguish between normal and stroke subjects with different lesion's severity.
Studies in health technology and informatics 02/2009; 150:794-8.
[Show abstract][Hide abstract] ABSTRACT: We exploited time irreversibility analysis to characterize short heart period sequences (256 samples) derived from 24h Holter recordings in normal healthy (NO) subjects and chronic heart failure (CHF) patients. We found a significant presence of irreversible dynamics over short time scales, whereas over dominant, longer time scales irreversibility was marginal. Over short time scales in NO subjects the percentage of irreversible dynamics was larger during daytime than during nighttime, thus indicating a larger presence of non linear dynamics during daytime. Same circadian variation was detected in CHF patients but the percentage of irreversible series was higher. In NO subjects during daytime the non linear behavior was mostly the result of bradycardic runs shorter than tachycardic ones. In CHF population this pattern was as present as the reverse pattern (i.e. tachycardic runs shorter than bradycardic ones). Time irreversibility analysis provides useful and reliable indexes even in uncontrolled experimental conditions and during daily activities.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2008; 2008:2116-9.
[Show abstract][Hide abstract] ABSTRACT: We propose an integrated approach based on uniform quantization over a small number of levels for the evaluation and characterization of complexity of a process. This approach integrates information-domain analysis based on entropy rate, local nonlinear prediction, and pattern classification based on symbolic analysis. Normalized and non-normalized indexes quantifying complexity over short data sequences ( approximately 300 samples) are derived. This approach provides a rule for deciding the optimal length of the patterns that may be worth considering and some suggestions about possible strategies to group patterns into a smaller number of families. The approach is applied to 24 h Holter recordings of heart period variability derived from 12 normal (NO) subjects and 13 heart failure (HF) patients. We found that: (i) in NO subjects the normalized indexes suggest a larger complexity during the nighttime than during the daytime; (ii) this difference may be lost if non-normalized indexes are utilized; (iii) the circadian pattern in the normalized indexes is lost in HF patients; (iv) in HF patients the loss of the day-night variation in the normalized indexes is related to a tendency of complexity to increase during the daytime and to decrease during the nighttime; (v) the most likely length L of the most informative patterns ranges from 2 to 4; (vi) in NO subjects classification of patterns with L=3 indicates that stable patterns (i.e., those with no variations) are more present during the daytime, while highly variable patterns (i.e., those with two unlike variations) are more frequent during the nighttime; (vii) during the daytime in HF patients, the percentage of highly variable patterns increases with respect to NO subjects, while during the nighttime, the percentage of patterns with one or two like variations decreases.
Chaos An Interdisciplinary Journal of Nonlinear Science 04/2007; 17(1):015117. · 1.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To evaluate the relationship between lesion's severity and nonlinear indexes of HRV, 20 first-ever stroke subjects and 10 healthy subjects were studied. All patients, divided in two groups according to presence of single or multiple medium cerebral artery lesion, underwent to a 24-hour Hotter ECG recording. All RR time series were analyzed by Poincare Plot, fractal dimension, power-law behaviour, spectral and time- domain techniques. A direct relationship between increasing lesion's severity and progressive collapsing of PPlots and FD index was observed, while lower significance were found for beta exponent, spectral and time-domain parameters. These results suggest that PPlots and FD analysis contains relevant information related to different HRV dynamics in normal and stroke subjects with different lesion's severity.
[Show abstract][Hide abstract] ABSTRACT: We assessed the clinical correlates of a comprehensive set of non-linear heart rate variability (HRV) indices computed from 24-h Holter recordings for 200 stable chronic heart failure (CHF) patients [median age (lower quartile, upper quartile) 54 (47, 58) years, LVEF 23% (19%, 28%)]. A total of 19 non-linear indices belonging to six major families, namely symbolic dynamics, entropy, empirical mode decomposition, fractality-multifractality, unpredictability and Poincaré plots, were considered. Most indices showed a significant association with ejection fraction and with the severity of symptoms, while only two (one each from the fractality and Poincaré plot families) showed an association with aetiology. Only one symbolic dynamics variable was associated with the presence of non-sustained ventricular tachycardia and two symbolic dynamics variables were associated with the rate of ventricular ectopic events. Our results demonstrate the existence of selective links between non-linear indexes of HRV and the clinical status and functional impairment of CHF patients. This indicates that further studies should be designed to investigate the physiopathological mechanisms involved in such links.