Resp Care
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Noninvasive ventilation (NIV) has assumed an important role in the management of certain types of respiratory failure in acute-care hospitals. However, the optimal location for NIV has been a matter of debate. Some have argued that all patients begun on NIV in the acute-care setting should go to an intensive care unit (ICU), but this is impractical because ICU beds are often unavailable, and it may not be a sensible use of resources. ⋯ Step-down units are often good locations for NIV, but many institutions do not have step-down units. With ICU beds at a premium, many hospitals are forced to manage some NIV patients on general wards, which can be safely done with more stable patients if the ward is suitably monitored and experienced. When deciding where to locate the patient, clinicians must be familiar with the capabilities of the units in their facility and try to match the patient's need for monitoring and the unit's capabilities.
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During noninvasive ventilation (NIV) for acute respiratory failure, the patient's comfort may be less important than the efficacy of the treatment. However, mask fit and care are needed to prevent skin damage and air leaks that can dramatically reduce patient tolerance and the efficacy of NIV. Choice of interface is a major determinant of NIV success or failure. ⋯ Technological issues to consider when choosing the NIV interface include dead space (dynamic, apparatus, and physiologic), the site and type of exhalation port, and the functioning of the ventilator algorithm with different masks. Heating and humidification may be needed to prevent adverse effects from cool dry gas. Heated humidifier provides better CO(2) clearance and lower work of breathing than does heat-and-moisture exchanger, because heated humidifier adds less dead space.
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The physiologic effects of noninvasive ventilation (NIV) on work of breathing (WOB) and breathing pattern, respiratory-system mechanics, and hemodynamic function were examined via a literature review of clinical studies done between 1990 and 2008. Forty-one relevant studies were found; the majority examined patients with chronic obstructive pulmonary disease, whereas some also included patients with restrictive chest-wall disease or acute hypoxic respiratory failure. NIV reduced WOB in direct proportion to the level of inspiratory pressure-assist, and also by the ability of applied positive end-expiratory pressure (PEEP) to counter intrinsic PEEP. ⋯ At high levels of inspiratory pressure-assist, NIV consistently increased dynamic lung compliance and tidal volume, and improved arterial blood gases. The hemodynamic effects of NIV are dependent upon the interplay between the type of mask, the level of inspiratory pressure-assist and PEEP, and the disease state. In general, patients with chronic obstructive pulmonary disease have a higher tendency toward decreased cardiac output at high levels of inspiratory pressure-assist, compared to those with acute lung injury.
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Noninvasive ventilation (NIV) in patients with acute respiratory failure (ARF), which was originally described decades ago, underwent a rebirth after reports of successful use in 1989. Over the following 18 years the literature on NIV has grown substantially. This paper summarizes the randomized controlled trials (RCTs) on NIV for acute respiratory failure. ⋯ We conclude that NIV for ARF is supported by strong evidence from patients with COPD, but there is only weak support for NIV in other patient groups, such as immunocompromised patients. For other groups, such as patients with asthma, pneumonia, or acute lung injury, RCT-level evidence is lacking or does not suggest benefit. Clearly, major gaps remain in our evidence base.
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Although noninvasive ventilation (NIV) was first used to treat patients with acute respiratory failure in the 1940s, the history of this mainstay of today's respiratory care armamentarium has mainly been written in the last 20 years. There is now a robust evidence base documenting the efficacy of NIV in exacerbations of chronic obstructive pulmonary disease, cardiogenic pulmonary edema, and acute respiratory failure in immunocompromised patients, and evidence in support of NIV in other settings, such as hypoxemic acute respiratory failure and the management of patients who decline endotracheal intubation, is accumulating rapidly. ⋯ However, although the expansion of its use in everyday patient care has lagged behind the growth of its evidence base, an increasing number of studies document the steadily expanding use of NIV in the acute-care setting. This article reviews the history of NIV as applied in acutely ill patients and summarizes the studies of NIV outside the research setting during the last decade.