Resp Care
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Mechanically, breath design is usually either flow/volume-targeted or pressure-targeted. Both approaches can effectively provide lung-protective ventilation, but they prioritize different ventilation parameters, so their responses to changing respiratory-system mechanics and patient effort are different. These different response behaviors have advantages and disadvantages that can be important in specific circumstances. ⋯ In contrast, pressure targeting, with its variable flow, may be easier to synchronize and will limit inspiratory pressure, but it provides no control over delivered volume. Skilled clinicians can maximize benefits and minimize problems with either flow/volume targeting or pressure targeting. Indeed, as is often the case in managing complex life-support devices, it is operator expertise rather than the device design features that most impacts patient outcomes.
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Low-tidal-volume ventilation strategies are clearly beneficial in patients with acute lung injury and acute respiratory distress syndrome, but the optimal level of applied positive end-expiratory pressure (PEEP) is uncertain. In patients with high pleural pressure on conventional ventilator settings, under-inflation may lead to atelectasis, hypoxemia, and exacerbation of lung injury through "atelectrauma." In such patients, raising PEEP to maintain a positive transpulmonary pressure might improve aeration and oxygenation without causing over-distention. ⋯ Recently the use of esophageal manometry to identify the optimal ventilator settings, avoiding both under-inflation and over-inflation, was proposed. This method shows promise but awaits larger clinical trials to assess its impact on clinical outcomes.
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Ventilator-associated pneumonia (VAP) is a common and serious complication of mechanical ventilation via an artificial airway. As with all nosocomial infections, VAP increases costs, morbidity, and mortality in the intensive care unit (ICU). ⋯ Substantial evidence supports the use of endotracheal tubes (ETTs) that allow subglottic suctioning; silver-coated and antiseptic-impregnated ETTs; ETTs with thin-walled polyurethane cuffs; and HMEs, but these devices also can have adverse effects. Controversy still exists regarding the evidence, cost-effectiveness, and disadvantages and risks of these devices.
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Advances in treating the critically ill have resulted in more patients requiring prolonged airway intubation and respiratory support. If intubation is projected to be longer than several weeks, tracheostomy is often recommended. Tracheostomy offers the potential benefits of improved patient comfort, the ability to communicate, opportunity for oral feeding, and easier, safer nursing care. ⋯ Based on the available data, we think it is reasonable to perform early tracheostomy in all patients projected to require prolonged mechanical ventilation. Unfortunately, identifying those patients can be difficult, and for many patient populations we lack the necessary tools to predict prolonged ventilation. We propose an early-tracheostomy decision algorithm.
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Review
Should prone positioning be routinely used for lung protection during mechanical ventilation?
Prone positioning has been known for decades to improve oxygenation in animals with acute lung injury and in most patients with acute respiratory distress syndrome (ARDS). The mechanisms of this improvement include a more uniform pleural-pressure gradient, a smaller volume of lung compressed by the heart, and more uniform and better-matched ventilation and perfusion. ⋯ However, several randomized trials have failed to show improvements in clinical outcomes of ARDS patients, other than consistently better oxygenation. Because each of these trials had design problems or early termination, prone positioning remains a rescue therapy for patients with acute lung injury or ARDS.