Respiratory care
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Noninvasive ventilation is an effective treatment for a significant proportion of patients with acute respiratory failure. The success of noninvasive ventilation, however, depends on several factors, a major one being the selection of the proper interface. The choice and application of the interface in patients with acute respiratory failure is a considerable challenge for any treatment team. This review discusses the different types of interfaces that can be used in patients with acute respiratory failure, the differences between nasal, oro-nasal, and total face masks and the helmet, as well as the effect of interface type on treatment success and upper airway patency, mask fitting, problems related to the interface, and the relationship between ventilator type and interface choice.
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This review describes the current understanding of the lungs' response to deforming stress under conditions of both normal physiology and acute lung injury. Several limiting assumptions are needed to infer lung parenchymal stress and strain from airway pressure, volume, and flow data from mechanically ventilated patients with injured lungs. These assumptions include the effects of the chest wall on lung-surface pressure, its topographical distribution, and the effects of non-uniform tissue properties on local parenchymal stresses. ⋯ Understanding both the assumptions of lung mechanics and the scope of injury mechanisms operating during ARDS is necessary to interpret the results of clinical trials that inform prevailing ventilator-management guidelines. The implications issuing from these 3 topics inform a safer approach to setting and adjusting the ventilator to minimize the risk of ventilator-induced lung injury. This is enumerated in a 5-step approach that can be used to guide ventilator management of unstable patients with severe lung injury.
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Heated and humidified high-flow nasal cannula (HFNC) is a widely used form of respiratory support; however, data regarding optimal flows for a given patient size or disease state are lacking. A comprehensive study of the physiologic effects of HFNC is needed to better understand the mechanisms of action. The objective of the current study was to quantify the effect of HFNC settings in age-specific, anatomically correct nasal airways and spontaneously breathing lung models. We hypothesized that there is an effect of flow on pressure and ventilation. ⋯ These findings may help clinicians understand the effects of HFNC at different settings and may inform management guidelines for patients with respiratory failure.
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Simulation studies are often used to examine ventilator performance. However, there are no standards for selecting simulation parameters. This study collected data in passively-ventilated adult human subjects and summarized the results as a set of parameters that can be used for simulation studies of intubated, passive, adult subjects with normal lungs, COPD, or ARDS. ⋯ This study provides educators, researchers, and manufacturers with a standard set of practical parameters for simulating the respiratory system's mechanical properties in passive conditions.
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Noninvasive ventilation (NIV) is used to treat respiratory failure in patients with concomitant need for aerosol delivery. Limited pediatric data are available on aerosol delivery efficiency, and none at all regarding aerosol delivery efficiency with a double-limb circuit. We compared the effect of position in the double-limb ventilator circuit, types of nebulizer, and ventilator settings on aerosol delivery efficiency in a pediatric model of NIV. We hypothesized that placing a vibrating mesh nebulizer at the ventilator and using the highest inspiratory pressures would increase aerosol delivery efficiency. ⋯ In a pediatric model of NIV, the effect of nebulizer position on aerosol delivery efficiency depends on the type of device and its placement in the ventilator circuit. A vibrating mesh nebulizer placed at the mask or before the Y-piece of the double-limb circuit provided the highest aerosol drug delivery during NIV. Data generated with invasive ventilation models should not be generalized to NIV models.