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Search Results: 1 - 10 of 6924 matches for " Paolo Pelosi "
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Soluble proteins of chemical communication: an overview across arthropods
Paolo Pelosi
Frontiers in Physiology , 2014, DOI: 10.3389/fphys.2014.00320
Abstract: Detection of chemical signals both in insects and in vertebrates is mediated by soluble proteins, highly concentrated in olfactory organs, which bind semiochemicals and activate, with still largely unknown mechanisms, specific chemoreceptors. The same proteins are often found in structures where pheromones are synthesized and released, where they likely perform a second role in solubilizing and delivering chemical messengers in the environment. A single class of soluble polypeptides, called Odorant-Binding Proteins (OBPs) is known in vertebrates, while two have been identified in insects, OBPs and CSPs (Chemosensory Proteins). Despite their common name, OBPs of vertebrates bear no structural similarity with those of insects. We observed that in arthropods OBPs are strictly limited to insects, while a few members of the CSP family have been found in crustacean and other arthropods, where however, based on their very limited numbers, a function in chemical communication seems unlikely. The question we address in this review is whether another class of soluble proteins may have been adopted by other arthropods to perform the role of OBPs and CSPs in insects. We propose that lipid-transporter proteins of the Niemann-Pick type C2 family could represent likely candidates and report the results of an analysis of their sequences in representative species of different arthropods.
Tracheostomy must be individualized!
Paolo Pelosi, Paolo Severgnini
Critical Care , 2004, DOI: 10.1186/cc2966
Abstract: Tracheostomy is among the most frequently conducted procedures in critically ill patients [1]. It has advantages compared with translaryngeal endotracheal intubation, including reduced laryngeal anatomical alteration, reduced inspiratory load, and better patient tolerance and ease of nursing. Thus, tracheostomy can enhance patient care in the event of prolonged respiratory support and difficulty in weaning.In the study conducted by Arabi and colleagues [2], those investigators examined the frequency with which tracheostomy was conducted; pathophysiological characteristics of patients undergoing early (first week in the intensive care unit [ICU]) and late tracheostomy (> 7 days in the ICU); and the impact of early tracheostomy on the duration of mechanical ventilation, ICU length of stay and outcomes in a selected population of trauma patients. They reported that the majority of patients underwent tracheostomy after the first week, and that patients who received tracheostomy within the first week had maxillofacial trauma and more severe neurological injuries. Multivariate analysis showed that early tracheostomy was associated with reduced ICU length of stay. That study presents several issues that require consideration when interpreting the findings. First, the data are from a single population of patients with severe neurological and maxillofacial trauma. Second, both surgical and percutaneous tracheostomy techniques were performed. Finally, the percutaneous techniques used in the study were not reported.The optimal timing of tracheostomy remains controversial. The results presented suggest that early tracheostomy may reduce ICU length of stay and resource utilization in severe trauma, which is in accordance with previous data reported in patients with acute respiratory failure [3], but early tracheostomy did not reduce hospital length of stay or mortality. A recent study [4], performed in medical intensive care patients, showed that early percutaneous dilational tr
Tracheostomy – a multiprofessional handbook
Paolo Pelosi, Paolo Severgnini
Critical Care , 2005, DOI: 10.1186/cc2993
Abstract: It is a 392-page paperback book with 22 chapters covering the following topics: first, the upper airway and respiratory basic anatomy; second, the technical basis of tracheostomy and how it alters the upper airway's anatomy; third, the description of different tracheostomy tubes and surgical or percutaneous tracheostomy approaches; fourth, the medical and nursing care of tracheostomy in the early phase after the operation and in the long term, including humidification, suctioning, wound care, swallowing and communication; fifth, the problems related to changing the tracheostomy tube and decannulation; sixth, particular attention to the technical and practical problems of tracheostomy of children; seventh, infection management and nutritional care of the tracheostomized patient.Particularly important are the sections dedicated to tracheostomy problems in children. Tracheostomy in children is not as common as in adults, but when it occurs both the technical aspects, namely tracheostomy timing and technique, and clinical management are particularly difficult even for more experienced doctors. Moreover, few contributions have been published on this specific aspect. In this book the authors describe the main differences in anatomy, tracheostomy tubes, techniques, and nursing management between tracheostomy in children and in adults. Extremely emotional is the report of the parents of a tracheostomized daughter describing aspects of their practical experience and psychological behaviour. It looks like a charming tale but it gives important information to doctors and nurses that are generally unrecognized and unconsidered.Surprisingly poor is the section dedicated to percutaneous techniques. The authors mention only one specific dilational technique. It should be remembered that several percutaneous techniques, intrusive and extrusive, are now commercially available and each of them has advantages and disadvantages that have to be addressed individually when a specific tra
Clinical review: Positive end-expiratory pressure and cardiac output
Thomas Luecke, Paolo Pelosi
Critical Care , 2005, DOI: 10.1186/cc3877
Abstract: Cyclic opening and closing of atelectatic alveoli and distal small airways with tidal breathing is known to be a basic mechanism leading to ventilator-induced lung injury [1]. To prevent alveolar cycling and derecruitment in acute lung injury, high levels of positive end-expiratory pressure (PEEP) have been found necessary to counterbalance the increased lung mass resulting from edema, inflammation and infiltrations and to maintain normal functional residual capacity (FRC) [2]. Therefore, application of high levels of PEEP is often recommended [3], despite the fact that 'aggressive' mechanical ventilation using high levels of PEEP to maintain or restore oxygenation during acute lung injury can markedly affect cardiac function in a complex and often unpredictable fashion. Likewise, this notion holds true for intrinsic PEEP caused by ventilation with high respiratory rates resulting in dynamic hyperinflation. Except from the failing ventricle, PEEP usually decreases cardiac output, a well known fact since the classic studies of Cournand et al. [4], in which the effects of positive-pressure ventilation were measured. They concluded that positive-pressure ventilation restricted the filling of the right ventricle because the elevated intrathoracic pressure (ITP) restricted venous flow into the thorax and, thereby, reduced cardiac output. This formulation of intrathoracic responses to positive-pressure ventilation still is the basis of our present day understanding of the cardiopulmonary interactions induced by PEEP, although precise responses to PEEP have not been simple to prove, and the intrathoracic responses appear multiple and complex.As heart rate usually does not change with PEEP [5], the entire fall in cardiac output is a consequence of a reduction in left ventricular (LV) stroke volume (SV). Therefore, the discussion on PEEP-induced changes in cardiac output can be confined to analyzing changes in SV and its determinants: preload, afterload, contractility and ve
The lung and the brain: a dangerous cross-talk
Paolo Pelosi, Patricia RM Rocco
Critical Care , 2011, DOI: 10.1186/cc10259
Abstract: The study by Quilez and colleagues [1] in this issue of Critical Care reports morpho-functional and biochemical effects of mechanical ventilation with lower (8 mL/kg) and higher (30 mL/kg) tidal volume (VT) on lung and brain in healthy rats. Mechanical ventilation may have a serious impact on lung structure and function, leading to ventilator-associated lung injury (VALI) as well as promoting damage of peripheral organs, including the brain. In this respect, mechanical ventilation and sedation in healthy and diseased lungs have been reported to be associated with neurologic impairment, memory, and cognitive dysfunction [2]. On the other hand, brain injury may enhance lung damage in experimental settings [3], probably by promoting a higher rate of pulmonary complications as well as by altering neurologic outcome [4]. Overall, the information in regard to the multiplepathway cross-talk between the brain and lungs is quite limited [5].In the study by Quilez and colleagues [1], different variables, including lung function, plasma, and lung levels of cytokines as well as c-fos gene, were measured. c-fos is a marker of neuronal activation and is correlated with an increase in functional and metabolic activity in the brain, involved in the phenomena of neuronal plasticity, expressed in response to a wide range of stimuli, and implicated in processes such as gene transcription, apoptosis, or proliferation [6]. The main results of the study by Quilez and colleagues can be summarized as follows: (a) independently of higher or lower VT, mechanical ventilation 'per se' (compared with spontaneous breathing) induced neutrophil infiltration, increased lung damage, and was associated with a greater release of inflammatory markers in both the lung and plasma as well as c-fos activation in central amygdala, hippocampus, paraventricular hypothalamic nuclei, and supraoptic nucleus; and (b) higher VT increased c-fos in the retrosplenial cortex and hypotalamus and increased tumor necrosi
Airway closure: the silent killer of peripheral airways
Paolo Pelosi, Patricia RM Rocco
Critical Care , 2007, DOI: 10.1186/cc5692
Abstract: In this issue of Critical Care, Jain and Sznajder [1] consider the role played by the peripheral airways during mechanical ventilation in various pathologies. During mechanical ventilation the end-inspiratory transpulmonary pressure (stress), determined by tidal volume, fluctuates and has been proposed to be the main determinant of ventilator-induced lung injury (VILI) [2]. However, stress is not the sole determinant of VILI, and strain (the ratio between tidal volume and end-expiratory lung volume [EELV]) may also play a role.Four specific mechanisms that may lead to VILI have been identified. First, regional over-distension caused by application of local stress or pressure forces cells and tissues to assume shapes and dimensions that they would not during unassisted breathing. The second mechanism, the so-called 'low EELV injury' associated with repeated recruitment and de-recruitment of unstable lung units, causes abrasion of the epithelial airspace lining as a result of interfacial forces. Third, surfactant may be deactivated by large alveolar surface area oscillations that stress surfactant adsorption and desorption kinetics and are associated with surfactant aggregate conversion. Fourth, and finally, interdependence mechanisms elevate cell and tissue stress between neighbouring structures with differing mechanical properties. However, little attention has been given to the role played by reduced EELV and airway closure in mediating damage to peripheral airways during mechanical ventilation with 'physiological' tidal volumes in healthy lungs [3].Peripheral airways are defined as airways that are less than 2 mm in diameter and consist of small membranous, terminal and respiratory bronchioles, as well as alveolar ducts. The small membranous and terminal bronchioles have conductive functions, whereas respiratory bronchioles and alveolar ducts can have both conducting and gas-exchanging functions. They have no cartilage and so they can easily collapse at low EELV (
Investigation on Harmonic Tuning for Active Ku-Band Rectangular Dielectric Resonator Antennas
Anda Guraliuc,Giuliano Manara,Paolo Nepa,Giuseppe Pelosi,Stefano Selleri
International Journal of Antennas and Propagation , 2008, DOI: 10.1155/2008/437538
Abstract: A slot-coupled rectangular dielectric resonator antenna (DRA) operating in the 14–14.5 GHz frequency band is investigated as a possible radiating element for an active integrated antenna of a transmitting phased array. The effectiveness of the resonator shape factor on achieving harmonic tuning is addressed. Simulation results show that the DRA shape factor can be used to provide a fine tuning of the DRA input impedance both at the fundamental frequency and its first harmonics, so synthesizing the proper load for the optimization of the microwave amplifier power-added efficiency (PAE).
Effects of positive end-expiratory pressure on respiratory function and hemodynamics in patients with acute respiratory failure with and without intra-abdominal hypertension: a pilot study
Joerg Krebs, Paolo Pelosi, Charalambos Tsagogiorgas, Markus Alb, Thomas Luecke
Critical Care , 2009, DOI: 10.1186/cc8118
Abstract: Twenty patients with ALI/ARDS with normal IAP or IAH treated in the surgical intensive care unit in a university hospital were studied. The mean IAP in patients with IAH and normal IAP was 16 ± 3 mmHg and 8 ± 3 mmHg, respectively (P < 0.001). At different PEEP levels (5, 10, 15, 20 cmH2O) we measured respiratory mechanics, partitioned into its lung and chest wall components, alveolar recruitment, gas-exchange, hemodynamics, extravascular lung water index (EVLWI) and intrathoracic blood volume index (ITBVI).We found that ALI/ARDS patients with IAH, as compared to those with normal IAP, were characterized by: a) no differences in gas-exchange, respiratory mechanics, partitioned into its lung and chest wall components, as well as hemodynamics and EVLWI/ITBVI; b) decreased elastance of the respiratory system and the lung, but no differences in alveolar recruitment and oxygenation or hemodynamics, when PEEP was increased at 10 and 15cmH2O; c) at higher levels of PEEP, EVLWI was lower in ALI/ARDS patients with IAH as compared with those with normal IAP.IAH, within the limits of IAP measured in the present study, does not affect interpretation of respiratory mechanics, alveolar recruitment and hemodynamics.Over the past decade there has been a marked increase in interest in the role of intra-abdominal pressure (IAP) in critically ill patients [1]. The World Society of Abdominal Compartment Syndrome (WSACS) defined intra-abdominal hypertension (IAH) as a sustained or repeated pathological elevation in IAP of 12 mmHg or more [2,3] observed in 54.4% and 65.0% of medical and surgical critically ill patients, respectively [4]. IAH has been shown to negatively affect various organ functions [1], including the respiratory system [5] and hemodynamics [6].Acute lung injury (ALI) and adult respiratory distress syndrome (ARDS) are characterized by an increase in elastance of the respiratory system (Estat, RS), mainly attributed to the elastance of the lung (Estat, L). However, altera
New and conventional strategies for lung recruitment in acute respiratory distress syndrome
Paolo Pelosi, Marcelo de Abreu, Patricia RM Rocco
Critical Care , 2010, DOI: 10.1186/cc8851
Abstract: Mechanical ventilation is a supportive and life saving therapy in patients with acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Despite advances in critical care, mortality remains high [1]. During the last decade, the fact that mechanical ventilation can produce morphologic and physiologic alterations in the lungs has been recognized [2]. In this context, the use of low tidal volumes (VT) and limited inspiratory plateau pressure (Pplat) has been proposed when mechanically ventilating the lungs of patients with ALI/ARDS, to prevent lung as well as distal organ injury [3]. However, the reduction in VT may result in alveolar derecruitment, cyclic opening and closing of atelectatic alveoli and distal small airways leading to ventilator-induced lung injury (VILI) if inadequate low positive end-expiratory pressure (PEEP) is applied [4]. On the other hand, high PEEP levels may be associated with excessive lung parenchyma stress and strain [5] and negative hemodynamic effects, resulting in systemic organ injury [6]. Therefore, lung recruitment maneuvers have been proposed and used to open up collapsed lung, while PEEP counteracts alveolar derecruitment due to low VT ventilation [4]. Lung recruitment and stabilization through use of PEEP are illustrated in Figure 1. Nevertheless, the beneficial effects of recruitment maneuvers in ALI/ARDS have been questioned. Although Hodgson et al. [7] showed no evidence that recruitment maneuvers reduce mortality or the duration of mechanical ventilation in patients with ALI/ARDS, such maneuvers may be useful to reverse life-threatening hypoxemia [8] and to avoid derecruitment resulting from disconnection and/or airway suctioning procedures [9].The success and/or failure of recruitment maneuvers are associated with various factors: 1) Different types of lung injury, mainly pulmonary and extra-pulmonary origin; 2) differences in the severity of lung injury; 3) the transpulmonary pressures reached during recruitment man
Respiratory and haemodynamic changes during decremental open lung positive end-expiratory pressure titration in patients with acute respiratory distress syndrome
Christian Gernoth, Gerhard Wagner, Paolo Pelosi, Thomas Luecke
Critical Care , 2009, DOI: 10.1186/cc7786
Abstract: A software programme (Open Lung Tool?) incorporated into a standard ventilator controlled the recruitment (pressure-controlled ventilation with fixed PEEP at 20 cmH2O and increased driving pressures at 20, 25 and 30 cmH2O for two minutes each) and PEEP titration (PEEP lowered by 2 cmH2O every two minutes, with tidal volume set at 6 ml/kg). The open lung PEEP (OL-PEEP) was defined as the PEEP level yielding maximum dynamic respiratory compliance plus 2 cmH2O. Gas exchange, respiratory mechanics and central haemodynamics using the Pulse Contour Cardiac Output Monitor (PiCCO?), as well as transoesophageal echocardiography were measured at the following steps: at baseline (T0); during the final recruitment step with PEEP at 20 cmH2O and driving pressure at 30 cmH2O, (T20/30); at OL-PEEP, following another recruitment manoeuvre (TOLP).The ratio of partial pressure of arterial oxygen (PaO2) to fraction of inspired oxygen (FiO2) increased from T0 to TOLP (120 ± 59 versus 146 ± 64 mmHg, P < 0.005), as did dynamic respiratory compliance (23 ± 5 versus 27 ± 6 ml/cmH2O, P < 0.005). At constant PEEP (14 ± 3 cmH2O) and tidal volumes, peak inspiratory pressure decreased (32 ± 3 versus 29 ± 3 cmH2O, P < 0.005), although partial pressure of arterial carbon dioxide (PaCO2) was unchanged (58 ± 22 versus 53 ± 18 mmHg). No significant decrease in mean arterial pressure, stroke volume or cardiac output occurred during the recruitment (T20/30). However, left ventricular end-diastolic area decreased at T20/30 due to a decrease in the left ventricular end-diastolic septal-lateral diameter, while right ventricular end-diastolic area increased. Right ventricular function, estimated by the right ventricular Tei-index, deteriorated during the recruitment manoeuvre, but improved at TOLP.A standardised open lung strategy increased oxygenation and improved respiratory system compliance. No major haemodynamic compromise was observed, although the increase in right ventricular Tei-index and right v
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