Biomedical subjects

A Pedotti

Publications and source records attributed to A Pedotti.

At least 19 recordsLinked to original sources

PubMed2006

Oxygen kinetics and debt during recovery from expiratory flow-limited exercise in healthy humans.

In healthy subjects expiratory flow limitation (EFL) during exercise can lower O(2) delivery to the working muscles. We hypothesized that if this affects exercise performance it should influence O(2) kinetics at the end of exercise when the O(2) debt is repaid. We performed an incremental exercise test on six healthy males with a Starling resistor in the expiratory line limiting expiratory flow to approximately 1 l s(-1) to determine maximal EFL exercise workload (W (max)). In two more square-wave exercise runs subjects exercised with and without EFL at W (max) for 6 min, while measuring arterial O(2) saturation (% SaO(2)), end-tidal pressure of CO(2) (P (ET)CO(2)) and breath-by-breath O(2) consumption VO2 taking into account changes in O(2) stored in the lungs. Over the last minute of EFL exercise, mean P (ET)CO(2) (54.7 +/- 9.9 mmHg) was significantly higher (P < 0.05) compared to control (41.4 +/- 3.9 mmHg). At the end of EFL exercise %SaO(2) fell significantly by 4 +/- 3%. When exercise stopped, EFL was removed, and we continued to measure VO2. During recovery, there was an immediate step increase in [Formula: see text] so that repayment of EFL O(2) debt started at a higher VO2 than control. Recovery VO2 kinetics after EFL exercise was best characterized by a double-exponential function with fundamental and slow time constants of 27 +/- 11 and 1,020 +/- 305 s, compared to control values of 41 +/- 10 and 1,358 +/- 320 s, respectively. EFL O(2) debt was 52 +/- 22% greater than control (2.19 +/- 0.58 vs. 1.49 +/- 0.38 l). We conclude that EFL exercise increases the O(2) debt and leads to hypoxemia in part due to hypercapnia.

Carbon Dioxide↗

PubMed2006

Expiratory flow limitation detected by forced oscillation and negative expiratory pressure.

The within-breath change in reactance (Delta(rs)) measured by forced oscillation technique (FOT) at 5 Hz reliably detects expiratory flow limitation in chronic obstructive pulmonary disease (COPD). The present study compared this approach to the standard negative expiratory pressure (NEP) method. In total, 21 COPD patients were studied by applying both techniques to the same breath and in 15 patients the measurements were repeated after bronchodilator. For each patient and condition five NEP tests were performed and independently scored by three operators unaware of the FOT results. In 180 tests, FOT classified 53.3% as flow limited. On average, the operators scored 27.6% of tests flow limited and 47.6% non-flow limited, but could not score 24.8%. The methods disagreed in 7.9% of cases; in 78% of these the NEP scores differed between operators. Bronchodilation reduced NEP and DeltaX(rs) scores, with only the latter achieving significance. Averaging the operators' NEP scores, a threshold between 24.6-30.8% of tidal volume being flow limited by NEP produced 94% agreement between methods. In conclusion, when negative expiratory pressure and forced oscillation technique were both available they showed good agreement. As forced oscillation technique is automatic and can measure multiple breaths over long periods, it is suitable for monitoring expiratory flow limitation continuously and identifying patients' breathing close to the onset of expiratory flow limitation, where intermittent sampling may be unrepresentative.

Forced Expiratory Flow Rates↗

PubMed2006

A neural network based method for optical patient set-up registration in breast radiotherapy.

Patient set-up optimization is required in breast-cancer radiotherapy to fill the accuracy gap between personalized treatment planning and uncertainties in the irradiation set-up. Opto-electronic systems allow implementing automatic procedures to minimize the positional mismatches of light-reflecting markers located on the patient surface with respect to a corresponding reference configuration. The same systems are used to detect the position of the irradiated body surface by means of laser spots; patient set-up is then corrected by matching the control points onto a CT based reference model through surface registration algorithms. In this paper, a non-deterministic approach based on Artificial Neural Networks is proposed for the automatic, real-time verification of geometrical set-up of breast irradiation. Unlike iterative surface registration methods, no passive fiducials are used and true real-time performance is obtained. Moreover, the non-deterministic modeling performed by the neural algorithm minimizes sensitivity to intra-fractional and inter-fractional non-rigid motion of the breast. The technique was validated through simulated activities by using reference CT data acquired on four subjects. Results show that the procedure is able to detect and reduce simulated set-up errors and revealed high reliability in patient position correction, even when the surface deformation is included in testing conditions.

Breast Neoplasms↗

PubMed2006

Noninvasive detection of expiratory flow limitation in COPD patients during nasal CPAP.

The difference between mean inspiratory and expiratory respiratory reactance (delta(rs)) measured with forced oscillation technique (FOT) at 5 Hz allows the detection of expiratory flow limitation (EFL) in chronic obstructive pulmonary disease (COPD) patients breathing spontaneously. This aim of this study was to evaluate whether this approach can be applied to COPD patients during noninvasive pressure support. Delta(rs) was measured in seven COPD patients subjected to nasal continuous positive airway pressure (CPAP) at 0, 4, 8 and 12 cmH2O in sitting and supine positions. Simultaneous recording of oesophageal pressure and the Mead and Whittenberger (M-W) method provided a reference for scoring each breath as flow-limited (FL), non-flow-limited (NFL) or indeterminate (I). For each patient, six consecutive breaths were analysed for each posture and CPAP level. According to M-W scoring, 47 breaths were FL, 166 NFL and 51 I. EFL scoring using FOT coincided with M-W in 94.8% of the breaths. In the four patients who were FL in at least one condition, delta(rs) was reduced with increasing CPAP. These data suggest that the forced oscillation technique may be useful in chronic obstructive pulmonary disease patients on nasal pressure support by identifying continuous positive airway pressure levels that support breathing without increasing lung volume, which in turn increase the work of breathing and reduce muscle effectiveness and efficiency.

Aged↗

PubMed2005

Behavioral outcomes following below-knee amputation in the coordination between balance and leg movement.

Lateral leg movement is accompanied by opposite movements of the supporting leg and trunk segments. This kinematic synergy shifts the center of mass (CM) towards the supporting foot and stabilizes its final position, while the leg movement is being performed. The aim of the present study was to provide insight in the behavioral substitution process responsible for the performance of this kinematic synergy. The kinematic synergy was assessed by the principal component analysis (PCA) applied to both hip joints and supporting ankle joint. Patients after unilateral below-knee amputation and control subjects were asked to perform a lateral leg raising. The first principal component (PC(1)) accounted for more than 99% of the total angular variance for all subjects (amputees and controls). PC(1) thus well represents the possibility to describe this complex multi-joint movement as a one degree of freedom movement with fixed ratios between joint angular time course. In control subjects, the time covariation between joints changes holds during all phases of the leg movement (postural phase, ascending and braking phases). In amputees, PC(1) score decreased during the ascending phase of the movement (i.e. when the body weight transfer is completed, while the movement is initiated). We conclude that a feedback mechanism is involved and discuss the hypothesis that this inter-joint coordination in amputees results from a failure in the pre-setting of the inter-joint coupling.

Adult↗

PubMed2005

Influence of expiratory flow-limitation during exercise on systemic oxygen delivery in humans.

To determine the effects of exercise with expiratory flow-limitation (EFL) on systemic O(2) delivery, seven normal subjects performed incremental exercise with and without EFL at approximately 0.8 l s(-1) (imposed by a Starling resistor in the expiratory line) to determine maximal power output under control (W'(max,c)) and EFL (W'(max,e)) conditions. W'(max,e) was 62.5% of W'(max,c), and EFL exercise caused a significant fall in the ventilatory threshold. In a third test, after exercising at W'(max,e) without EFL for 4 min, EFL was imposed; exercise continued for 4 more minutes or until exhaustion. O(2) consumption (V'(O)(2)) was measured breath-by-breath for the last 90 s of control, and for the first 90 s of EFL exercise. Assuming that the arterio-mixed venous O(2) content remained constant immediately after EFL imposition, we used V'(O)(2) as a measure of cardiac output (Q'(c)). Q'(c) was also calculated by the pulse contour method with blood pressure measured continuously by a photo-plethysmographic device. Both sets of data showed a decrease of Q'(c) due to a decrease in stroke volume by 10% (p < 0.001 for V'(O)(2)) with EFL and remained decreased for the full 90 s. Concurrently, arterial O(2) saturation decreased by 5%, abdominal, pleural and alveolar pressures increased, and duty cycle decreased by 43%. We conclude that this combination of events led to a decrease in venous return secondary to high expiratory pressures, and a decreased duty cycle which decreased O(2) delivery to working muscles by approximately 15%.

Adult↗

PubMed2005

Effect of salbutamol on lung function and chest wall volumes at rest and during exercise in COPD.

BACKGROUND: Inhaled bronchodilators can increase exercise capacity in chronic obstructive pulmonary disease (COPD) by reducing dynamic hyperinflation, but treatment is not always effective. This may reflect the degree to which the abdomen allows dynamic hyperinflation to occur. METHOD: A double blind, randomised, crossover trial of the effect of 5 mg nebulised salbutamol or saline on endurance exercise time was conducted in 18 patients with COPD of mean (SD) age 67.1 (6.3) years and mean (SD) forced expiratory volume in 1 second (FEV1) of 40.6 (15.0)% predicted. Breathing pattern, metabolic variables, dyspnoea intensity, and total and regional chest wall volumes were measured non-invasively by optoelectronic plethysmography (OEP) at rest and during exercise. RESULTS: Salbutamol increased FEV1, forced vital capacity (FVC) and inspiratory capacity and reduced functional residual capacity (FRC) and residual volume significantly. OEP showed the change in resting FRC to be mainly in the abdominal compartment. Although the mean (SE) end expiratory chest wall volume was 541 (118) ml lower (p<0.001) at the end of exercise, the endurance time was unchanged by the bronchodilator. Changes in resting lung volumes were smaller when exercise duration did not improve, but FEV1 still rose significantly after active drug. After the bronchodilator these patients tried to reduce the end expiratory lung volume when exercising, while those exercising longer continued to allow end expiratory abdominal wall volume to rise. The change to a more euvolumic breathing pattern was associated with a lower oxygen pulse and a significant fall in endurance time with higher isotime levels of dyspnoea. CONCLUSIONS: Nebulised salbutamol improved forced expiratory flow in most patients with COPD, but less hyper-nflated patients tried to reduce the abdominal compartmental volume after active treatment and this reduced their exercise capacity. Identifying these patients has important therapeutic implications, as does an understanding of the mechanisms that control chest wall muscle recruitment.

Aged↗

PubMed2005

Derivation of centers and axes of rotation for wrist and fingers in a hand kinematic model: methods and reliability results.

In the field of 3D reconstruction of human motion from video, model-based techniques have been proposed to increase the estimation accuracy and the degree of automation. The feasibility of this approach is strictly connected with the adopted biomechanical model. Particularly, the representation of the kinematic chain and the assessment of the corresponding parameters play a relevant role for the success of the motion assessment. In this paper, the focus is on the determination of the kinematic parameters of a general hand skeleton model using surface measurements. A novel method that integrates nonrigid sphere fitting and evolutionary optimization is proposed to estimate the centers and the functional axes of rotation of the skeletal joints. The reliability of the technique is tested using real movement data and simulated motions with known ground truth 3D measurement noise and different ranges of motion (RoM). With respect to standard nonrigid sphere fitting techniques, the proposed method performs 10-50% better in the best condition (very low noise and wide RoM) and over 100% better with physiological artifacts and RoM. Repeatability in the range of a couple of millimeters, on the localization of the centers of rotation, and in the range of one degree, on the axis directions is obtained from real data experiments.

Adult↗

PubMed2004

Kinematical models to reduce the effect of skin artifacts on marker-based human motion estimation.

The estimation of the skeletal motion obtained from marker-based motion capture systems is known to be affected by significant bias caused by skin movement artifacts, which affects joint center and rotation axis estimation. Among different techniques proposed in the literature, that based on rigid body model, still the most used by commercial motion capture systems, can smooth only part of the above effects without eliminating their main components. In order to sensibly improve the accuracy of the motion estimation, a novel technique, named local motion estimation (LME), is proposed. This rests on a recently described approach that, using virtual humans and extended Kalman filters, estimates the kinematical variables directly from 2D measurements without requiring the 3D marker reconstruction. In this paper, we show how such method can be extended to include the computation of the local marker displacement due to skin artifacts. The 3D marker coordinates, expressed in the corresponding local reference coordinate frames, are inserted into the state vector of the filter and their dynamics is automatically estimated, with adequate accuracy, without assuming any particular deformation function. Simulated experiments of lower limb motion, involving systematic mislocations (5, 10, 20 mm) and random errors of the marker coordinates and joint center locations (+/-5, +/-10, +/-15 mm), have shown that artifact motion can be substantially decoupled from the global skeletal motion with an effective increase of the accuracy wrt standard techniques. In particular, the comparison between the nominal kinematical variables and the one recovered from markers attached to the skin surface proved LME to be sensibly superior (50% in the worse condition) to the methods imposing marker-bone rigidity. In conclusion, while requiring further validation on real movement data, we argue that the proposed method can constitute an appropriate approach toward the improvement of the human motion estimation.

Biomechanical Phenomena↗

PubMed2004

Effects of bilateral subthalamic stimulation on gait kinematics and kinetics in Parkinson's disease.

Subthalamic nucleus (STN) stimulation, a recent surgical approach to Parkinson's disease (PD), has been shown to be effective in relieving motor symptoms. The present study carried out a full body gait analysis, during overground walking, on ten PD patients with bilaterally implanted STN stimulation devices. Walking performance was analyzed on the same day, in four conditions (Stim Off-Med Off, Stim On-Med Off, Stim Off-Med On, Stim On-Med On). The results showed that, on average, STN stimulation alone (S+M-) and L-dopa alone (S-M+), significantly increased gait speed, stride length and the lower limb joint Range of Motion (ROM) with respect to the basal condition (S-M-); also cadence was found to play a role in velocity increase, particularly when L-dopa was administered. Both treatments improved pelvis and trunk kinematics, and power production at the ankle and hip joints. The combination of the two treatments (S+M+) produced an additional effect on gait speed, stride length, ROM of knee and ankle joints, pelvis obliquity and trunk inclination. Given the additive and synergistic effects, it can be hypothesized that the two treatments have different mechanisms of action. Our results confirm the findings of earlier studies that employed treadmill walking.

Aged↗

PubMed2004

Kinematics of head-trunk movements while entering and exiting a car.

The study of free and natural accessibility movements for a medium-sized car was carried out, recording the motor performances of ten participants by means of a motion analysis system. The experimental protocol used passive markers to implement a two-segment biomechanical model for the analysis of the head-trunk complex. The kinematic variables quantify the motor patterns, and showed specific features that can be related to the individual anthropometric characteristics and to the car geometry differences: tall participants used a neck flexion and a leftwards bending of the head, while short participants extended the neck and bent the head to the right. The different seat positions (short participants move forwards the seat) along with the principal need to avoid any body interference with the car, can explain the observed strategies. From the wider analysis of the movements in relation to the vehicle's features and to the anthropometric size of the participants, this approach could lead to an extension of the design criteria for those structural components of the car which have been demonstrated to significantly influence the human-machine interaction.

Abdomen↗

PubMed2004

Microprocessor-controlled optical stimulating device to improve the gait of patients with Parkinson's disease.

Different types of visual cue for subjects with Parkinson's disease (PD) produced an improvement in gait and helped some of them prevent or overcome freezing episodes. The paper describes a portable gait-enabling device (optical stimulating glasses (OSGs) that provides, in the peripheral field of view, different types of continuous optic flow (backward or forward) and intermittent stimuli synchronised with external events. The OSGs are a programmable, stand-alone, augmented reality system that can be interfaced with a PC for program set-up. It consists of a pair of non-corrective glasses, equipped with two matrixes of 70 micro light emitting diodes, one on each side, controlled by a microprocessor. Two foot-switches are used to synchronise optical stimulation with specific gait events. A pilot study was carried out on three PD patients and three controls, with different types of optic flow during walking along a fixed path. The continuous optic flow in the forward direction produced an increase in gait velocity in the PD patients (up to + 11% in average), whereas the controls had small variations. The stimulation synchronised with the swing phase, associated with an attentional strategy, produced a remarkable increase in stride length for all subjects. After prolonged testing, the device has shown good applicability and technical functionality, it is easily wearable and transportable, and it does not interfere with gait.

Aged↗

PubMed2004

Evolutionary optimization for robust hierarchical computation of the rotation centres of kinematic chains from reduced ranges of motion the lower spine case.

A novel technique based on evolutionary optimization is proposed here to compute the average rotation centres (RCs) of ball joints linked into kinematic chains using 3D trajectories of the markers attached to the external surface of the corresponding articulated structures. The chain is hierarchically solved by iteratively minimizing the variance of the marker distances from the actual RC through an evolutional strategy method (ESM) from proximal to distal joints. In particular, the technique is compared to the non-rigid sphere-fitting method, recently proposed in literature and implemented through a closed-form solution (CFS), in conditions of random and systematic noise superimposed to the marker coordinates. Results from simulated motions showed that, in case of small range of motion (5 degrees , 10 degrees ) the performance of CFS is really unreliable whereas ESM provided satisfactory accuracy. Error propagation along the kinematic chain was found to be negligible. Also in the case of systematic errors, ESM provides an accuracy that is sensibly better than that of the CFS. As a case study, ESM was applied to the in vivo computation of the RCs of the vertebrae in the lower spine region using a specific marker protocol. A set of spine movements by a normal adult male, recorded by an optoelectronic motion capture system, were processed with the developed method. The variability of the estimated average RCs was small (few millimeters) in agreement with the literature data from cadaveric studies and X-ray imaging.

Algorithms↗

PubMed2004

Non-invasive approach towards the in vivo estimation of 3D inter-vertebral movements: methods and preliminary results.

A kinematical model of the lower spine was designed and used to obtain a robust estimation of the vertebral rotations during torso movements from skin-surface markers recorded by video-cameras. Markers were placed in correspondence of the anatomical landmarks of the pelvic bone and vertebral spinous and transverse processes, and acquired during flexion, lateral bending and axial motions. In the model calibration stage, a motion-based approach was used to compute the rotation axes and centres of the functional segmental units. Markers were mirrored into virtual points located on the model surface, expressed in the local reference system of coordinates. The spine motion assessment was solved into the domain of extended Kalman filters: at each frame of the acquisition, the model pose was updated by minimizing the distances between the measured 2D marker projections on the cameras and the corresponding back-projections of virtual points located on the model surface. The novelty of the proposed technique rests on the fact that the varying location of the rotation centres of the functional segmental units can be tracked directly during motion computation. In addition, we show how the effects of skin artefacts on orientation data can be taken into account. As a result, the kinematical estimation of simulated motions shows that orientation artefacts were reduced by a factor of at least 50%. Preliminary experiments on real motion confirmed the reliability of the proposed method with results in agreement with classical studies in literature.

Algorithms↗

PubMed2004

ELITE-S2: the multifactorial movement analysis facility for the International Space Station.

Experimental observations of adaptation processes of the motor control system to altered gravity conditions can provide useful elements to the investigations on the mechanisms underlying motor control of human subject. The microgravity environment obtained on orbital flights represents a unique experimental condition for the monitoring of motor adaptation. The research in motor control exploits the changes caused by microgravity on the overall sensorimotor process, due to the impairment of the sensory systems whose function depends upon the presence of the gravity vector. Motor control in microgravity has been investigated during parabolic flights and short-term space missions, in particular for analysis of movement-posture co-ordination when equilibrium is no longer a constraint. Analysis of long-term adaptation would also be very interesting, calling for long-term body motion observations during the process of complete motor adaptation to the weightlessness environment. ELITE-S2 is an innovative facility for quantitative human movement analysis in weightless conditions onboard the International Space Station (ISS). ELITE-S2 is being developed by the Italian Space Agency, ASI is to be delivering the flight models to NASA to be included in an expressed rack in US Lab Module in February 2004. First mission is currently planned for summer 2004 (increment 10 ULF 2 ISS).

Adaptation, Physiological↗

PubMed2004

Effects of subthalamic nucleus stimulation and L-dopa in trunk kinematics of patients with Parkinson's disease.

In the advanced phase of Parkinson's disease (PD), high frequency electrical stimulation (HFS) of the subthalamic nucleus (STN) can represent a good therapeutic option, whose effects on walking have been recently quantified by kinematic and dynamic gait analysis. The goal of the present study was to compare, in a group of PD patients, the effects of STN stimulation and of L-dopa on trunk kinematics during walking. The additive effect of these two treatments was investigated as well. Ten idiopathic PD patients implanted bilaterally with a STN stimulation system and ten age-matched controls were studied using a three dimensional motion analyser. Four conditions were considered: with (s+) and without (s-) STN stimulation and with (m+) and without (m-) L-dopa administration. The results showed that both stimulation alone and L-dopa alone significantly increased the stride length and the gait speed, with an additional effect if applied simultaneously. Cadence was more influenced by L-dopa. The range of lateral bending and torsion of the trunk, which were reduced in s-/m-, increased similarly in s-/m+ and in s+/m- conditions. The exaggerated forward inclination of the trunk reduced towards control values in all therapeutic conditions. There was a tendency for L-dopa to increase trunk movements in the frontal plane, similar to events seen in quiet stance. Due to the presence of additive and synergistic effects, we concluded that the mechanisms of action of the two treatments are likely to be different.

Aged↗

PubMed2004

Regional chest wall volumes during exercise in chronic obstructive pulmonary disease.

BACKGROUND: Dynamic hyperinflation of the lungs impairs exercise performance in chronic obstructive pulmonary disease (COPD). However, it is unclear which patients are affected by dynamic hyperinflation and how the respiratory muscles respond to the change in lung volume. METHODS: Using optoelectronic plethysmography, total and regional chest wall volumes were measured non-invasively in 20 stable patients with COPD (mean (SD) forced expiratory volume in 1 second 43.6 (11.6)% predicted) and dynamic hyperinflation was tracked breath by breath to test if this was the mechanism of exercise limitation. Resting ventilation, breathing pattern, symptoms, rib cage and abdominal volumes were recorded at rest and during symptom limited cycle ergometry. Pleural, abdominal, and transdiaphragmatic pressures were measured in eight patients. RESULTS: End expiratory chest wall volume increased by a mean (SE) of 592 (80) ml in 12 patients (hyperinflators) but decreased by 462 (103) ml in eight (euvolumics). During exercise, tidal volume increased in euvolumic patients by reducing end expiratory abdominal volume while in hyperinflators tidal volume increased by increasing end inspiratory abdominal and rib cage volumes. The maximal abdominal pressure was 22.1 (9.0) cm H(2)O in euvolumic patients and 7.6 (2.6) cm H(2)O in hyperinflators. Euvolumic patients were as breathless as hyperinflators but exercised for less time and reached lower maximum workloads (p<0.05) despite having better spirometric parameters and a greater expiratory flow reserve. CONCLUSIONS: Dynamic hyperinflation is not the only mechanism limiting exercise performance in patients with stable COPD. Accurate measurement of chest wall volume can identify the different patterns of respiratory muscle activation during exercise.

Aged↗

PubMed2004

Enhanced surface registration techniques for patient positioning control in breast cancer radiotherapy.

Experimental data, describing patient inter-fractional set-up errors in the clinical practice of breast radiotherapy, were exploited to simulate the performance in errors detection and correction of a constrained surface registration procedure, based on a hybrid configuration of control points (passive and laser). During 47 treatment sessions in three patients undergoing post-quadrantectomy radiotherapy, an opto-electronic localizer was used to acquire the three-dimensional coordinates of the hybrid control points, being two passive markers placed on selected skin landmarks on the sternum. Laser scanning technique was also applied for the acquisition of the 3-D surface model of the irradiated body area, which was used as reference for the automatic position correction procedure. A constrained surface registration algorithm was applied to estimate the rigid spatial transformation, describing the local errors affecting the control points. The improvement of the irradiation geometrical set-up, by correcting the patient position according to the estimated spatial transformation parameters, was simulated. Results showed that the proposed surface registration method allowed us to detect and significantly (Wilcoxon signed rank analysis) reduce the initial misalignments, which exhibited overall median and 75th percentile values equal to 4.26 mm and 5.76 mm. Simulated residual errors dropped down to median and 75th percentile values measuring 2.95 mm and 3.87 mm, respectively. These results confirmed the high potentiality of surface registration techniques for the opto-electronic automatic patient positioning control in breast cancer radiotherapy.

Algorithms↗