Resp Care
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A number of adjuncts to mechanical ventilation have been the focus of recent research. Automatic tube compensation (the regulation of airway pressure by estimation of tracheal pressure) appears to be an ideal approach to unloading the resistive effort imposed by the endotracheal tube. Randomized controlled trials have recently been performed with high frequency oscillation (HFO), partial liquid ventilation (PLV), and prone positioning. ⋯ With both HFO and prone positioning we will have to wait for additional randomized clinical trials before the status of those techniques can be determined. No randomized trials of tracheal gas insufflation have been performed. Of major concern with tracheal gas insufflation is the lack of a commercial product.
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Increased understanding of the mechanisms and effects of acute respiratory failure has not been accompanied by more precise criteria by which the clinician can determine when intubation should be carried out and invasive positive-pressure ventilation (IPPV) instituted in a given patient. The indications traditionally offered in reviews and textbooks have tended to be either so broad as not to be very helpful in an individual case, or of questionable clinical relevance and too cumbersome for practical use. This review updates the indications for IPPV in adult patients with acute respiratory failure by examining available evidence from clinical trials and by considering new management alternatives that have become available in the last 20 years. ⋯ However, in other settings of acute hypoxemic respiratory failure, such as acute lung injury and acute respiratory distress syndrome, this has not been shown. The use of IPPV may improve outcomes in patients with severe cardiogenic shock. However, IPPV has not proven to be beneficial in traumatic brain injury and flail chest, in the absence of other indications.
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The tremendous progress in microprocessor-driven ventilator technology over the last years has facilitated the introduction of a broad variety of different ventilatory modes into the clinical practice of mechanical ventilation. Many of these newer modalities are designed for partial ventilatory support, which might reflect the complexity of the issue of patient ventilator interactions when spontaneous breathing activity is present compared to controlled mechanical ventilation. There are reasons to believe that allowing some degree of spontaneous breathing activity during mechanical ventilation is useful not only to gradually withdraw ventilatory assistance in the process of weaning but also to avoid some of the adverse effects of mechanical ventilation in the early phase of acute respiratory failure when classically controlled modes of ventilation are used. It is the aim of this article to review the effects of preserved spontaneous breathing activity during mechanical ventilation with different ventilatory modalities in acute respiratory failure patients.
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Treatment of anxiety and delirium, provision of adequate analgesia, and, when necessary, amnesia in critically ill patients is humane and may reduce the incidence of post-traumatic stress disorders. Injudicious use of sedatives and paralytics to produce a passive and motionless patient, however, may prolong weaning and length of stay in the intensive care unit. ⋯ The choice of pharmacologic agents is made difficult by complex or poorly understood pharmacokinetics, drug actions, and adverse effects in critically ill patients. Advantages, adverse effects, and limitations of drug treatment, including use of neuromuscular blocking drugs and use of sedatives and analgesia during the withdrawal of life-sustaining measures are reviewed.
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To determine whether propofol affects spontaneous breathing patterns in critically ill patients recovering from respiratory failure during initial attempts at liberation from mechanical ventilation. ⋯ Propofol causes changes in breathing pattern that could lead a caregiver to erroneously conclude that a patient is not ready to begin spontaneous breathing trials. Since this effect has also been noted following benzodiazepine infusion, the clinician should consider the patient's "sedation history" when using RSBI to guide weaning decisions.