Resp Care
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Noninvasive positive pressure ventilation (NPPV) has been studied in several settings and shown to reduce patient morbidity associated with endotracheal intubation. Intolerance to NPPV has been estimated at 25-33%, a substantial proportion of attempts to ventilate noninvasively. Bi-level pressure ventilators (BPVs) have been designed for NPPV, yet their response to changes in respiratory impedance has not been extensively evaluated. To determine responses of BPVs to changing impedance conditions, we tested 4 BPVs to evaluate the potential for intolerance. We also developed a mathematical model for BPV performance that accounted for impedance conditions, leak, pressure settings, and inspiratory flow cutoff level. ⋯ VT delivery and auto-PEEP generated by BPVs are highly dependent on the prevailing impedance condition. Though there are differences between BPV models, generally, performance was similar between the models tested. This report suggests that knowledge of both respiratory system impedance and the performance of the BPV in use are required to attend to inadequate VT delivery and auto-PEEP generation. Furthermore, the model predicts a relatively narrow range for inspiratory flow cutoff that provides adequate ventilatory support without causing hyperinflation in patients with obstructive conditions.
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Long-term oxygen therapy improves survival and quality of life in hypoxemic patients with chronic obstructive pulmonary disease (COPD). The need for long-term oxygen therapy should be determined when patients are medically stable. The Third Oxygen Consensus Conference recommended reevaluating patients 1-3 months after continuous oxygen therapy (COT) is initiated, if initiated when the patient is medically unstable. ⋯ In our study, most patients were clinically unstable when COT was prescribed, and a significant number of patients remained on COT without reevaluation. Up to 60% of those patients could potentially be discontinued from COT if appropriately reevaluated. Referring a patient initiated on COT to a pulmonary specialist for the proper use of oxygen is strongly recommended. Reevaluating such patients in a timely fashion and discontinuing unnecessary oxygen concentrators could possibly save $106-153 million per year in the United States.