The inverse problem for cardiac arrhythmias.

A cardiac arrhythmia is an abnormality in the rate or rhythm of the heart beat. We study a type of arrhythmia called a premature ventricular complex (PVC), which is typically benign, but in rare cases can lead to more serious arrhythmias or heart failure. There are three known mechanisms for PVCs: reentry, an ectopic focus, and triggered activity. We develop minimal models for each mechanism and attempt the inverse problem of determining which model (and therefore which mechanism) best describes the beat dynamics observed in an ambulatory electrocardiogram. We demonstrate our approach on a patient who exhibits frequent PVCs and find that their PVC dynamics are best described by a model of triggered activity. Better identification of the PVC mechanism from wearable device data could improve risk stratification for the development of more serious arrhythmias.

Long ECGs reveal rich and robust dynamical regimes in patients with frequent ectopy.

We have analyzed the electrocardiographic data collected during continuous 7-day ambulatory recordings in patients with frequent premature ventricular complexes (PVCs). We analyze the dependence of the frequency and patterns of PVCs on the heart rate and the time of the day. Patients display rhythms of a complex yet consistent structure. In a given patient, the pattern remains robust over different days and particular repetitive patterns appear at specific heart rates, suggesting the appearance of bifurcations in the dynamics. Over the course of 24 h, we find that in some patients, patterns appear to depend only on the heart rate, whereas in others, both the time of the day and the heart rate play a role in controlling the dynamics. Identifying parameter values at which bifurcations occur facilitates the development of dynamical models for arrhythmia. The use of powerful recording and analysis techniques will enable improved analysis of data and better understanding of mechanisms of arrhythmia in individual patients.

Detecting and distinguishing tipping points using spectral early warning signals.

Theory and observation tell us that many complex systems exhibit tipping points-thresholds involving an abrupt and irreversible transition to a contrasting dynamical regime. Such events are commonly referred to as critical transitions. Current research seeks to develop early warning signals (EWS) of critical transitions that could help prevent undesirable events such as ecosystem collapse. However, conventional EWS do not indicate the type of transition, since they are based on the generic phenomena of critical slowing down. For instance, they may fail to distinguish the onset of oscillations (e.g. Hopf bifurcation) from a transition to a distant attractor (e.g. Fold bifurcation). Moreover, conventional EWS are less reliable in systems with density-dependent noise. Other EWS based on the power spectrum (spectral EWS) have been proposed, but they rely upon spectral reddening, which does not occur prior to critical transitions with an oscillatory component. Here, we use Ornstein-Uhlenbeck theory to derive analytic approximations for EWS prior to each type of local bifurcation, thereby creating new spectral EWS that provide greater sensitivity to transition proximity; higher robustness to density-dependent noise and bifurcation type; and clues to the type of approaching transition. We demonstrate the advantage of applying these spectral EWS in concert with conventional EWS using a population model, and show that they provide a characteristic signal prior to two different Hopf bifurcations in data from a predator-prey chemostat experiment. The ability to better infer and differentiate the nature of upcoming transitions in complex systems will help humanity manage critical transitions in the Anthropocene Era.

IgE Ratio in Tears: A Predictive Tool of Ocular Allergic Inflammation.

PURPOSE: To demonstrate the tear IgE (measured/exuded) ratio (R) as a useful biological marker of ocular allergy in order to distinguish severe from less severe inflammatory status. METHODS: Tear samples and sera from 78 ocular allergy patients and 19 control subjects were analyzed. Total IgE and albumin were measured for calculating the tear IgE-R defining two subgroups (SG) of samples: R ≥ 4-SG and R < 4-SG. Eosinophil cationic protein, Th1 and Th2 cytokines (IFN-γ, IL-4, -5, -6, -8 and -10) and protein electrophoretic profiles were also investigated in tears. RESULTS: The R < 4-SG compared to the R ≥ 4-SG shows higher levels of tear albumin, eosinophil cationic protein, and Th1 and Th2 cytokines. Moreover, each subgroup presents a specific protein profile. CONCLUSION: This study showed that an IgE-R lower than four must be carefully interpreted as a warning sign of a severe inflammatory context and should be also associated with an exploration of immunological profile.

Direct access and patient/client self-referral to physiotherapy: a review of contemporary practice within the European Union.

BACKGROUND: Direct access refers to service users being able to refer themselves to physiotherapy without a third-party referral. It represents a model of practice supported globally by the profession, growing research evidence and health policy in some health systems. To the authors' knowledge, no research has been reported to ascertain the extent to which direct access is available within the physiotherapy profession within the European Union (EU). OBJECTIVES: To survey member organisations of the World Confederation for Physical Therapy (WCPT); establish the number of member states within the EU where it is possible for individuals seeking physiotherapy services to self-refer; describe the legislative/regulatory and reimbursement contexts in which physiotherapy services are delivered; examine if physiotherapy practice is different in member states where direct access is permitted compared with member states where direct access is not permitted; and to describe the barriers and facilitators to direct access perceived by member organisations of the WCPT. DESIGN: Cross-sectional, online survey using a purposive sample. PARTICIPANTS: Member organisations of the WCPT in the EU. RESULTS: Direct access is not available in all member states of the EU, despite the majority having legislation to regulate the profession, and entry-level education programmes that produce graduates with the requisite competencies. Key barriers perceived are those that can influence policy development, including the views of the medical profession and politicians. Support of service users and politicians, as well as professional autonomy, are seen as key facilitators. CONCLUSION: These results represent the first report of a comprehensive mapping of direct access to physiotherapy and contexts within the EU. In over half of member states, service users can self-refer to physiotherapists. These results provide insights to further individuals' understanding about the similarities and differences in working practices and service delivery factors, such as reimbursement across and within EU member states. The synergies between barriers and facilitators indicate the importance of targeted advocacy strategies in the introduction of direct access/self-referral to physiotherapy.

Contribution of positron emission tomography in pleural disease.

INTRODUCTION: Positron emission tomography (PET) now plays a clear role in oncology, especially in chest tumours. We discuss the value of metabolic imaging in characterising pleural pathology in the light of our own experience and review the literature. BACKGROUND: PET is particularly useful in characterising malignant pleural pathologies and is a factor of prognosis in mesothelioma. Metabolic imaging also provides clinical information for staging lung cancer, in researching the primary tumour in metastatic pleurisy and in monitoring chronic or recurrent pleural pathologies. CONCLUSIONS: PET should therefore be considered as a useful tool in the diagnosis of liquid or solid pleural pathologies.

Muscular strength, functional performances and injury risk in professional and junior elite soccer players.

Muscle strength and anaerobic power of the lower extremities are neuromuscular variables that influence performance in many sports activities, including soccer. Despite frequent contradictions in the literature, it may be assumed that muscle strength and balance play a key role in targeted acute muscle injuries. The purpose of the present study was to provide and compare pre-season muscular strength and power profiles in professional and junior elite soccer players throughout the developmental years of 15-21. One original aspect of our study was that isokinetic data were considered alongside the past history of injury in these players. Fifty-seven elite and junior elite male soccer players were assigned to three groups: PRO, n=19; U-21, n=20 and U-17, n=18. Players benefited from knee flexor and extensor isokinetic testing consisting of concentric and eccentric exercises. A context of lingering muscle disorder was defined using statistically selected cut-offs. Functional performance was evaluated throughout a squat jump and 10 m sprint. The PRO group ran faster and jumped higher than the U-17 group (P<0.05). No significant difference in isokinetic muscle strength performance was observed between the three groups when considering normalized body mass parameters. Individual isokinetic profiles enabled the identification of 32/57 (56%) subjects presenting lower limb muscular imbalance. Thirty-six out of 57 players were identified as having sustained a previous major lower limb injury. Of these 36 players, 23 still showed significant muscular imbalance (64%). New trends in rational training could focus more on the risk of imbalance and implement antagonist strengthening aimed at injury prevention. Such an intervention would benefit not only athletes recovering from injury, but also uninjured players. An interdisciplinary approach involving trainers, a physical coach, and medical staff would be of interest to consider in implementing a prevention programme.

[Pulmonary rehabilitation in chronic obstructive pulmonary disease]. / La réhabilitation pulmonaire dans la bronchopneumopathie chronique obstructive.

The current treatment of chronic obstructive pulmonary disease (COPD) patients must comprise, in addition to an optimal pharmacological treatment, a pulmonary rehabilitation, if possible multidisciplinary, and a program of post-rehabilitation in order to maintain the outcomes. Today pulmonary rehabilitation has proved to be effective in improving dyspnoea, exercise capacity and quality of life in COPD patients, and reducing the use of health services and thus the cost. In this article we want to present pulmonary rehabilitation, its indications and results, and the way by which it is held in the CHU of Liege.

[Testing aerobic power]. / Evaluation de la puissance aérobie en laboratoire: interprétation et implications pratiques pour le médecin du sport.

Maximal oxygen uptake (VO2 max) is regarded by some as the best single measurement of aerobic fitness. An other major determinant of successful endurance performance is the percentage of VO2 max that an athlete can maintain for a prolonged period. It is related to the lactate threshold. Two other factors also appear to be important for endurance activities as high economy of effort, or low VO2 value for the same rate of work; high percentage of ST muscle fibers. In the laboratory, the usual measurements of aerobic power include the determination of maximum oxygen consumption and the identification of lactate threshold. Testing aerobic power can help determine the type of aerobic training that should be emphasized.

[The contribution of positron emission tomography in pleural disease]. / Apport de l'imagerie par tomographie à émission de positons dans la pathologie pleurale. Intérêt de la TEP en pathologie pleurale.

INTRODUCTION: Positron emission tomography (PET) has a clear role in oncology, particularly in thoracic disease. In the light of our experience and a revue of the literature we define precisely the role of metabolic imaging in the diagnosis of pleural pathology. BACKGROUND: In particular PET allows characterisation of malignant pleural disease and provides prognostic information in mesothelioma. Metabolic imaging provides clinical information for the staging of pulmonary cancer, in the search for a primary tumour in metastatic pleurisy and also in the follow up of chronic or recurrent pleural pathology. CONCLUSIONS: It is justified, therefore, that PET joins the diagnostic armamentarium of pleural pathology, solid or liquid.

[Physiopathology of respiratory muscles]. / Dysfonction des muscles respiratoires.

Different factors can have deleterious effect the inspiratory muscles: increased intrinsic mechanical loading of the inspiratory muscles, functional inspiratory muscle weakness, increased ventilatory demand related to capacity... These muscle changes influence exercise tolerance and contribute to dyspnea.

[Physiologic requirements of high level gymnastics]. / Exigences physiologiques necessaires a la pratique de la gymnastique de haut niveau.

The evolution of the physiological profile of gymnasts over the past 40 years is outlined. Generally, gymnasts have a low aerobic aptitude in spite of an increase in the number of training hours. During the last decades, anaerobic power of gymnasts has increased. And now, the maximal power output measured by the Wingate test in high level male gymnasts is between 12 and 14 W.Kg-1 and in female gymnasts between 10 and 12 W.Kg-1. Measurement of higher blood lactate values also confirms that the anaerobic capacity has increased.

[Combining artificial tears---are they always synergistic?]. / L'association de substituts lacrymaux est-elle toujours synergique?

We report one case of thick, sticky, palpebral and conjunctival deposits following administration of artificial tears in a patient treated for dry eye syndrome. Experimental data confirmed clinical observation. The association of Refresh artificial tears and Dacudoses or Dacryoserum used as a washing solution should be avoided.

Increased TGFbeta1 plasma level in patients with lung cancer: potential mechanisms.

BACKGROUND: Plasma transforming growth factor beta1 (TGFbeta1) levels are elevated in patients with lung cancer. As TGFbeta1 is mainly found in platelets and as nonmalignant pulmonary diseases (NMPD) are frequently associated with lung cancer, we investigated the potential contribution of platelet degranulation and/or of a concomitant NMPD to the increased plasma levels of TGFbeta1 reported in patients with lung cancer. MATERIALS AND METHODS: Blood samples were collected in duplicate from 30 healthy subjects, 14 patients suffering from NMPD and 37 patients with lung cancer. The platelet count was determined and the samples were processed to obtain plasma. One sample was collected in EDTA (EDTA plasma) and the other in a mixture inhibiting platelet degranulation (PIM plasma). TGFbeta1 concentrations and beta-thromboglobulin (betaTG) levels, an index of platelet degranulation, were measured in both plasma samples. RESULTS: TGFbeta1 and betaTG plasma levels measured in PIM plasma were lower than those obtained in EDTA plasma. With respect to PIM plasma, both TGFbeta1 and betaTG levels were higher in patients with lung cancer than those with NMPD and in healthy individuals. In patients with NMPD, only TGFbeta1 levels were increased as compared to healthy controls, betaTG levels being similar. CONCLUSION: Methods for collecting and processing blood samples are critical in determining reliable circulating TGFbeta1 levels. Increased TGFbeta1 plasma levels observed in patients with lung cancer are related, at least partly, to concomitant NMPD and also to platelet degranulation as proved by increased betaTG levels.

[Exercise training in COPD]. / Le réentraînement à l'effort du patient BPCO.

Rehabilitation for patients with chronic obstructive pulmonary disease (COPD) is well established and widely accepted as a means of enhancing standard therapy in order to alleviate symptoms and optimize function. The primary goal of rehabilitation is to restore the patient to the highest possible level of independent function. There is, however, no consensus on the optimal training modalities. Both walking and cycling improve exercise performance; there is substantial evidence that lower extremity exercise training should be included in rehabilitation programs for patients with COPD.

[Physiologic evaluation of explosive force in sports]. / Evaluation physiologique de la force explosive du sportif.

Although we all possess the capability for anaerobic and aerobic energy metabolism, the capacity for each form of energy transfer varies considerably among individuals. Sports such as football or weightlifting, rely almost exclusively on energy derived from the muscles's pool of high-energy phosphates. Researchers have proposed different tests to estimate the power-generating capacity of high energy phosphates: stair-sprinting power tests, jumping-power tests or sprint cycling. In reality, however, it is difficult to obtain precise physiological or biochemical data during all-out exercise of brief duration.

[Exercise spirometry in medical practice]. / Ergospirométrie en pratique médicale.

Cardiopulmonary exercise testing is a unique tool to assess the limits and mechanisms of exercise tolerance. It is also useful for establishing the profiles and adequacy of the responses of the systems at submaximal and maximal exercises. The measure of VO2 max (maximal oxygen uptake) has become the "benchmark" to quantify cardiovascular functional capacity and aerobic fitness.