Respiratory care
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Respiratory ICUs (RICUs) have recently been implemented in France to fill the gap between ICUs and respiratory wards for patients who will require prolonged mechanical ventilation (PMV). The aim of this study was to describe the outcomes of subjects with tracheostomy who were undergoing PMV before and after implementing a RICU in our hospital. ⋯ Implementing a RICU improved the outcomes of the subjects with tracheostomy who were undergoing PMV by reducing the length of stay and increasing complete or partial weaning. However, the 1-year survival remained unchanged.
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Predicted values for pulmonary function tests differ significantly from the reference values used for many other diagnostic tests. Historically, simple equations using age, height, and sex were used to "predict" normal lung function. However, these multiple factors interact in complex ways to determine what the expected lung function values are in healthy subjects. ⋯ Modern equations use upper and lower limits of normal to offer a statistically robust means of defining who is within normal limits. Despite these advances, interpretation of pulmonary function test results has not been highly standardized, largely because interpretation depends on the reference equations used and, more importantly, how they are applied. This review discusses the strengths and limitations of using reference equations to interpret pulmonary function data in the context of research and clinical practice.
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The use of shared ventilation, or the simultaneous support of multiple patients connected in parallel to a single mechanical ventilator, is receiving considerable interest for addressing the severe shortage of mechanical ventilators available during the novel coronavirus pandemic (COVID-19). In this paper we highlight the potentially disastrous consequences of naïve shared ventilation, in which patients are simply connected in parallel to a ventilator without any regard to their individual ventilatory requirements. We then examine possible approaches for individualization of mechanical ventilation, using modifications to the breathing circuit that may enable tuning of individual tidal volumes and driving pressures during either volume-controlled ventilation (VCV) or pressure-controlled ventilation (PCV). ⋯ Of the shared ventilation strategies considered, shared PCV, with the inclusion of in-line pressure-relief valves in the individual inspiratory and expiratory limbs, offers the greatest degree of safety and lowest risk of catastrophic mechanical interactions between multiple patients connected to a single ventilator.
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The overwhelming demand for mechanical ventilators due to COVID-19 has stimulated interest in using one ventilator for multiple patients (ie, multiplex ventilation). Despite a plethora of information on the internet, there is little supporting evidence and no human studies. The risk of multiplex ventilation is that ventilation and PEEP effects are largely uncontrollable and depend on the difference between patients' resistance and compliance. It is not clear whether volume control ventilation or pressure control ventilation is safer or more effective. We designed a simulation-based study to allow complete control over the relevant variables to determine the effects of various degrees of resistance-compliance imbalance on tidal volume (VT), end-expiratory lung volume (EELV), and imputed pH. ⋯ These experiments confirmed the potential for markedly different ventilation and oxygenation for patients with uneven respiratory system impedances during multiplex ventilation. Three critical problems must be solved to minimize risk: (1) partitioning of inspiratory flow from the ventilator individually between the 2 patients, (2) measurement of VT delivered to each patient, and (3) provision for individual PEEP. We provide suggestions for solving these problems.