Presse Med
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Artificial ventilation plays a key role in the treatment of acute respiratory distress syndrome (ARDS). Initially, the goal is to normalize gas exchange compromised by the lung disease. Positive pressure ventilation can however aggravate prior lesions of the pulmonary parenchyma, at least in areas of the lung accessible to ventilation. ⋯ In the most severe cases, extra-corporal gas exchange systems have shown their efficacy for patients whose lungs cannot be ventilated. Thus ventilation should be carefully adapted to each patient based on the severity of the ARDS and its clinical course. We present a practical protocol based on a hierarchy rationale for each ventilation mode and indicate the explorations required to adapt each mode to a specific patient.
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Nosocomial pneumonia is associated with substantial morbidity and mortality. Patients treated with mechanical ventilation have the highest risk for developing this intensive care unit acquired infection. Gram-negative bacilli are the predominant organisms responsible for pneumonia in this setting. ⋯ Nosocomial pneumonia is difficult to diagnose clinically in ventilated patients because fever, lung infiltrate on chest X-ray, leukocytosis are frequent in severely ill patients under mechanical ventilation whatever lung infection is present or not and because lower respiratory tract of such patients is colonized by potentially pathogenic bacteria independently of the presence of true lung infection; thus, different diagnostic strategies are proposed. Our personal bias is that using bronchoscopic techniques to obtain bronchoalveolar lavage and protected-brush specimens permits us to devise a therapeutic strategy that is superior to one based only on clinical evaluation. Measures for prevention of nosocomial infection are essential to decrease the incidence of nosocomial pneumonia and the emergence of multiresistant pathogens.
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Experimental and clinical evidence has led to a revision of conventional techniques used for mechanical ventilation in the treatment of respiratory failure due to severe asthma and acute respiratory distress syndrome. A common feature in these two clinical situations is the heterogeneous nature of the lesions, causing mechanical alterations which vary from one region to another. Thus the tidal volume is not equally distributed throughout the lungs and can lead to overdistension in some regions or functional exclusion in others. ⋯ Controlled hypoventilation-or permissive hypercapnia-is a new approach aimed at preventing complications by supplying adequate oxygen while accepting or provoking a certain degree of hypercapnia by alveolar hypoventilation. The technique is based on restricting tidal volume and respiratory rate as long as is necessary to recover more favorable mechanical conditions. Results obtained with this method have been convincing for the treatment of decompensated asthma but preliminary data obtained in acute respiratory distress syndrome remain to be validated.
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When first developed in the fifties and sixties during the major polio epidemics, artificial ventilation was a major advance in medical care. The negative pressure perithoracic "iron lungs" had however many disadvantages and were widely replaced by positive pressure ventilation with intubation. This invasive technique allows normalization of gas exchange but has the disadvantage of requiring artificial sedation of the respiratory muscles in many cases in addition to the risk of secondary complications. ⋯ Other inconveniences include leaks around the mask and the need for careful surveillance by the health care workers. Today, there are several arguments based on prospective clinical studies showing that intubation may be avoided in certain patients by using non-invasive positive pressure ventilation with a nasal mask. Careful patient selection is however essential in addition to knowledge of the limitations of the technique.