Resp Care
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One of the most important aspects of caring for a critically ill patient is monitoring. Few would disagree that the most essential aspect of monitoring is frequent physical assessments. Complementing the physical examination is continuous monitoring of heart rate, respiratory rate, and blood oxygen saturation measured via pulse-oximetry, which have become the standard of care in intensive care units. ⋯ Based on the available literature, it seems reasonable to use continuous capnography, for at least a subset of critically ill patients, to ensure integrity of the endotracheal tube and other ventilatory apparatus. However, at this point definitive data are not yet available to clearly support continuous capnography for optimizing mechanical ventilatory support. We hope that as new data become available, the answer to this capnography question will become clear.
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Positive end-expiratory pressure (PEEP) and inspired oxygen fraction (F(IO(2))) are the primary means of improving P(aO(2)) during mechanical ventilation. Patients with acute respiratory distress syndrome (ARDS) typically present with a large intrapulmonary shunt, which makes even high F(IO(2)) ineffective in improving P(aO(2)). ⋯ The improved survival found in the National Institutes of Health's ARDS Network low-tidal-volume study may suggest that their PEEP/F(IO(2)) titration tables represent the best method for adjusting these variables. Based upon an extensive literature review of PEEP and respiratory system mechanics in ARDS, we conclude that: (1) for most patients the therapeutic range of PEEP is relatively narrow, so the ARDS Network PEEP/F(IO(2)) strategy is reasonable and supported by high-level evidence, (2) how best to adjust PEEP to prevent or ameliorate ventilator-associated lung injury is unknown and still under investigation, and (3) in a small subset of patients with severe lung injury and/or abnormal chest-wall compliance, highly individualized titration of PEEP, based upon the respiratory-system pressure-volume curve, PEEP/tidal-volume titration grids, or a recruitment maneuver and a PEEP decrement trial is a reasonable alternative.
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Airway pressure-release ventilation (APRV) is a mechanical ventilation strategy that is usually time-triggered but can be patient-triggered, pressure-limited, and time-cycled. APRV provides 2 levels of airway pressure (P(high) and P(low)) during 2 time periods (T(high) and T(low)), both set by the clinician. APRV usually involves a long T(high) and a short T(low). ⋯ Other ventilation modes also promote spontaneous breaths, but at overall lower end-inflation transpulmonary pressure. There is a dearth of data on what would be the optimal APRV inspiratory-expiratory ratio, positive end-expiratory pressure, or weaning strategy. The few clinical trials to date indicate that APRV provides adequate gas exchange, but none of the data indicate that APRV confers better clinical outcomes than other ventilation strategies.
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Ventilator-associated pneumonia (VAP) significantly increases intensive care unit morbidity, mortality, and costs. VAP is thought to be caused by bacterial entry into injured airways, which produces tracheobronchitis that evolves into diffuse pneumonia. The use of aerosolized antibiotics is conceptually attractive, especially when the infection is early and limited to the airway epithelium. ⋯ The clinical evidence for aerosolized antibiotics to prevent VAP is weak but suggestive. Concerns about the high cost, possible development of antibiotic resistance, and other potential risks of aerosolized antibiotics led several evidence-based consensus groups to recommend against routine use of aerosolized antibiotics for VAP prevention until better data are available. Importantly, the clinical evidence that aerosolized antibiotics can treat established VAP is negative, and multiple consensus groups recommend against treating established VAP with aerosolized antibiotics.
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Cardiac arrest is a common and lethal medical problem; each year more than half a million people in the United States and Canada suffer cardiac arrest treated by emergency medical personnel or in-hospital providers. Of those who survive to hospital admission or suffer in-hospital arrest, 40-60% die prior to discharge. Neurologic injury is the major source of morbidity and mortality after recovery of spontaneous circulation. ⋯ Clear consensus statements recommend that unconscious adult patients with spontaneous circulation after out-of-hospital cardiac arrest should be cooled if the initial rhythm was ventricular fibrillation, and that therapeutic hypothermia should be considered for other patients (other rhythms or in-hospital arrest). However, the position that all patients should be cooled following cardiac arrest is probably too broad, given the lack of studies on patients with non-ventricular-fibrillation rhythms, in-hospital arrest, or non-cardiac causes of arrest. Further research is needed to determine the broadest application of moderate therapeutic hypothermia.