Abstracts


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Oral Hygiene and Ventilator-Associated Pneumonia
Laurent Robriquet and François Fourrier

Oropharyngeal colonization with pathogenic organisms is a near-universal occurrence in critically ill patients receiving mechanical ventilation. Aspiration of these bacteria from the oral cavity and pharynx into the lower respiratory tract contributes to the development of ventilator-associated pneumonia (VAP). Colonization of dental plaque by Gramnegative bacteria has been recognized as an important contributor to the oropharyngeal bacterial pool in ICU patients. Lack of spontaneous movements of the tongue and jaws, reduction of salivary flow, infrequent swallowing, and inability to clean oral cavity and brush teeth because of orotracheal intubation or altered mental status result in biofilm and dental plaque formation. Oral hygiene has been proposed as a key intervention for reducing VAP. Strategies to eradicate oropharyngeal colonization by antiseptic oral care, such as chlorhexidine have been shown to reduce the oral microbial colonization and risk of VAP but failed to reduce duration of mechanical ventilation, ICU length of stay or mortality. Using chlorhexidine for oral antisepsis is simple and inexpensive with a low level of adverse effects but optimal concentration, technique and frequency of application warrant further studies.


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Tracheostomy - Causative or Preventive for Ventilator-Associated Pneumonia?
Denise P. Veelo, Jan M. Binnekade and Marcus J. Schultz

Ventilator-associated pneumonia (VAP) is a common complication in intubated and mechanically ventilated patients. A tracheostomy has been suggested to benefit patients with prolonged need for mechanical ventilation and may protect against VAP. However, a causal relationship between tracheostomy and VAP has also been suggested. This manuscript reviews the literature regarding the (causal) relationship between tracheostomy and VAP in adult critically ill patients.


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Ventilator-Associated Tracheobronchitis
Lucy B. Palmer

Purpose of Review: This review focuses on the pathophysiology of proximal airway infection in the ventilated patient. Ventilator-associated tracheobronchitis (VAT) is increasingly recognized as an important entity not only as an essential step in the pathway from oral colonization to deep lung infection but also as an infection associated with its own morbidity. Recent Findings: Multiple recent clinical trials have focused on the effects of new devices and treatment protocols on the morbidity associated with the progression of airway colonization to VAT or with the progression of VAT to VAP. Continuous subglottic secretion suctioning (CASS), innovative types of endotracheal tubes, and targeted therapy for VAT in recent investigations have shown promise in improving clinical outcomes in the critically ill patient. However, even with diligent attention to all the modifiable risk factors for respiratory infection, complete elimination of VAT and VAP remains unlikely. As long as a patient requires an endotracheal tube which disturbs airway integrity, host defenses will be impaired, and resistant virulent organisms which result from our liberal use of systemic antibiotics will continue to challenge critical care specialists. Summary: This review will focus on: 1) the current understanding of the pathogenesis of VAT, 2) modifiable risk factors, and 3) new approaches to treatment and bacterial resistance challenges.


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Opioid Use and Ventilator-Associated Pneumonia
Demosthenes Makris, Rémy Lubret and Saad Nseir

Opioids are routinely used to provide analgesia in mechanically ventilated patients. Opioid use is associated with increased risk of ICU-acquired infection, particularly VAP. Prolongation of exposure to mechanical ventilation, microaspiration, gastrointestinal motility disturbances, and immunomodulatory effects are the potential mechanisms by which opioids may favour VAP in these patients. Activation of sympathic nervous system, and hypothalamic-pituitary- adrenal axis was identified after morphine withdrawal. In addition, suppression of mitogen-stimulated proliferation of T and B-lymphocytes, natural killer activity, antibody production, IL2, IL12, INFγ, and NO production are the main immune effects observed during acute and chronic morphine exposure. The use of short acting opioids is associated with shorter duration of mechanical ventilation and ICU stay, and might be helpful in preventing VAP. Future studies should compare the effect of different opioid agents, and the impact of progressive opioid discontinuation compared with abrupt discontinuation on VAP incidence.


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Prevention of Endotracheal Tube Biofilm Formation in Intubated Critically Ill Patients
Lorenzo Berra and Asheesh Kumar

Endotracheal tubes (ETT) of intubated patients are constantly challenged with abundant bacteria-laden secretions. Quickly those bacteria may organize in a well-organized structure (biofilm) which is difficult to eradicate. Fragments can detach spontaneously or become dislodged by suction catheters and enter the lungs representing a source of infection. Recently several strategies have been developed to prevent bacterial biofilm formation and secretion accumulation. In this review we summarized published studies on ETT-biofilm prevention. Numerous antimicrobial-impregnated ETT have been designed to provide either bactericidal/static properties, or to prevent adhesion of bacteria on its surface. In vitro experiments and animal-studies showed several success rates in the prevention of bacterial colonization of the tube. Up to now, only two coatings, silver-hydrogel and silver-sulfadiazine in polyurethane, have been tested in clinical trials. Both proved to prevent/lower bacterial colonization of the ETT, while only the silver-hydrogel coating decreased bacterial colonization of lungs in a large multicenter study. Another innovative approach is to reduce contaminated-secretions in the ETT-lumen with novel medical devices designed to retrieve accumulated-mucus from the ETT/trachea. The mucus shaver and the mucus slurper are intended to reduce loaded-bacteria secretions from within the ETT/trachea. While experimental studies are promising, no clinical trials have been performed yet to prove this novel concept.


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Optimal oxygen therapy in the critically ill patient with respiratory failure
Gerard McHugh and Ross Freebairn

Whatever the aetiology and whatever the severity, the active management of respiratory failure habitually results in the administration of supplemental oxygen therapy. This review re-examines aspects of the optimization of such therapy. The oft-cited and well described risks of oxygen toxicity are revisited. Although no universal absolutes can be stipulated, the safe use of oxygen therapy is explored with particular reference to optimal oxygen targets. Specific attention is directed to the balance between the tolerable lower limits of systemic oxygenation and the putatively safe limits for titration of supplemental inspired oxygen fraction. Additional consideration is given to the emerging concept of permissive hypoxaemia. The attractiveness of this notion, and its potential role when the adverse effects of pursuing increased oxygenation combine to outweigh any benefit, has been enhanced by recent experiences with severe hypoxic respiratory failure arising from pandemic influenza viruses. Significant shortcomings remain in the existing definitions and descriptors of dysoxia, as well as the available technology for monitoring oxygenation. In clinical practice, oxygen displays a relatively narrow therapeutic index, and requires a careful balance of its benefits and risks. A detailed understanding of this ubiquitous therapy is obligatory in the optimal care of the critically ill.


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Aerosol Drug Administration with Helium-Oxygen (Heliox) Mixtures: An Overview
Arzu Ari and James B. Fink

Aerosol drug administration using helium-oxygen mixtures as a carrier gas has been advocated in the treatment of severe airway obstruction. Helium's low density has been shown to reduce resistance of gas flow through restricted airways passages, work of breathing, and minute ventilation requirements. Thus, it improves aerosol delivery in patients with acute airway obstruction, during both spontaneous breathing and mechanical ventilation. Although heliox has been shown to improve deposition of particles into the lung, the clinical evidence supporting the benefit of heliox is mixed. This review of the literature from 1934 - 2009 includes a brief review of the history of use of heliox in respiratory medicine, its physical properties and how they relate to the potential effects, limitations, and practical considerations associated with heliox-driven aerosol drug administration in acute and critically ill patients.


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Changes in lung function after compressed air diving
Anne Wilson

Diving using compressed air involves the potential for changing lung function through several mechanisms, including bronchial responsiveness. Of particular interest is the effect self-contained underwater breathing apparatus (SCUBA) may have on airflow limitation following a dive such as a possible result of aerosolization of seawater within the regulator, breathing cold dry gas from the tank, or some other putative mechanisms. This cross-sectional observational study was conducted in the field and investigated the hypothesis that bronchoconstriction may occur during a SCUBA dive in some individuals. Measurements included forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and peak expiratory flow. Spirometry instrumentation provided immediate feedback regarding test quality. Data were collected from May 2007-May 2009, at which time we calculated the data had an 88% statistical power to detect the clinically significant mean change in FEV1 of 200mls. Post-dive lung function values showed no clinically important impairment (FVC fell by 80 mls on average, 95% confidential interval CI 20mls to 140 mls, t(131)=2.57, p=0.01) and the hypothesis was not supported. Of 209 eligible divers who participated in the study, 63% provided valid spirometry data to ERS/ATS standards for acceptability and reproducibility. This study was conducted in the field as opposed to the more commonly used laboratory setting. Although spirometry is a simple test, the ease of data collection was made more difficult by environmental conditions and variables outside the researchers' control.


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Congenital Parenchymal Lesions of the Lung
Nada Sudhakaran and Mark Davenport

Increasing use of ultrasonography during pregnancy has uncovered a range of parenchymal lesions within the lung, some of which will, if left, be a cause of morbidity and occasional mortality. These include congenital cystic adenomatoid malformations (CCAM), bronchopulmonary sequestration (BPS), congenital lobar & segmental emphysema and bronchogenic cysts. Adverse antenatal features include mediastinal shift, caval obstruction, and (rarely) hydrops. This review aims to define current thoughts on these lesions and suggest appropriate management.


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Respiratory gas exchange during exercise in children with congenital heart disease: Methodology and clinical concepts
Tim Takken, A. Christian Blank and Erik Hulzebos

Cardiopulmonary exercise testing (CPET) in pediatric patients differs in many aspects from the tests as performed in adults. Children's cardiopulmonary responses during exercise testing present different characteristics, particularly indices of respiratory gas exchange (e.g. oxygen uptake, ventilation and ventilatory efficiency), which are essential in interpreting hemodynamic data. Diseases that are associated with myocardial ischemia are very rare in children. Important indications for CPET in children are the evaluation of exercise capacity and the non-invasive identification of pathologic features. In this article we will review the methodology, and clinical concepts exercise testing and interpretation of respiratory gas-exchange during exercise in children with congenital heart disease.