Respiratory care
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Functional residual capacity (FRC) is essentially the alveolar volume and a determinant of both oxygenation and respiratory system compliance (CRS). ARDS decreases FRC, and sufficient PEEP restores FRC; thus, assessments of PEEP by its impact on oxygenation and CRS are intimately linked. PEEP also can ameliorate or aggravate ventilator-induced lung injury. ⋯ Moreover, ambiguities and technical limitations in advanced techniques, such as esophageal manometry and pressure-volume curves, add a layer of complexity that renders its broader application in all ARDS patients both impractical and unnecessary. Whether sophisticated monitoring of chest mechanics in severe ARDS might improve outcomes further is open to question and should be studied further. However, it is highly improbable that we will ever discover a PEEP strategy that optimizes all aspects of cardiorespiratory function and chest mechanics for individual patients suffering from ARDS.
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In patients with ventilator-associated pneumonia, systemic use of antibiotics is the cornerstone of medical management. Supplemental use of aerosolized antibiotics with intravenous antibiotics in both experimental and clinical studies has been shown to have the following pharmacologic benefits: (1) aerosolized antibiotics reach the infected lung parenchyma without crossing the pulmonary alveolar capillary barrier; (2) aerosolized antibiotics increase anti-bacterial efficacy through increased local antibiotic concentration; and (3) aerosolized antibiotics decrease systemic toxicity. These benefits may be particularly beneficial to treat pneumonia caused by multidrug-resistant pathogens. ⋯ Studies to date have not clearly shown improvements in time to extubation, mortality, or other patient-centered outcomes. At present, amikacin, colistin, and ceftazidime are the most frequently used and studied aerosolized antibiotics. This review summarizes the characteristics of aerosolized antibiotics, reviews the advantages and disadvantages of using aerosolized antibiotics, and calls for future investigations based on animal study data.
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The use of neuromuscular blocking agents (NMBAs) early in the development of ARDS has been a strategy of interest for many years. The use of NMBAs with a concomitant deep sedation strategy can increase oxygenation and possibly decrease mortality when used in the early stages of ARDS. ⋯ The use of NMBA and deep sedation for these patients is not without consequence. This discussion describes the rationale and evidence behind the use of NMBAs in the setting of ARDS.
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Weaning from mechanical ventilation involves the reduction or withdrawal of ventilatory support in proportion to the patient's ability to sustain spontaneous ventilation. Protocolized weaning has been shown to reduce weaning duration; however, its weakness lies in the reliance on human intervention. Automated weaning is theoretically superior to manual weaning because of its ability to rapidly recognize deviations from desired behavior and enforce compliance with a standardized weaning strategy unencumbered by external influences. Whether currently available methods for automated weaning fulfill that potential to achieve superiority depends on patient type, care environment, and cause of ventilator dependence.
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It has been shown that mechanical ventilation by itself can cause lung injury and affect outcomes. Ventilator-induced lung injury is associated with high tidal volumes in lungs afflicted with ARDS. However, the question is: Do high tidal volumes have this same effect in normal lungs or lungs that have respiratory compromise stemming from something other than ARDS? Many clinicians believe that a tidal volume strategy of 6 mL/kg predicted body weight should be standard practice in all patients receiving mechanical ventilation. There is a growing body of evidence related to this issue, and this is the debate that will be tackled in this paper from both pro and con perspectives.