benefits of NIV


Noninvasive respiratory support methods—including noninvasive positive pressure ventilation delivered via face mask—have revolutionized the management of respiratory failure and facilitated early weaning and extubation of patients. However, benefit has not been seen in all patient groups, and in patients with severe acute hypoxemic respiratory (defined as PaO2/FiO2 ratio less than 150), early use of noninvasive ventilation (NIV) has not been shown to reduce the high rates of intubation (choice B is correct).

Methods of noninvasive respiratory support for patients with acute respiratory failure have long included use of CPAP or bilevel inspiratory and expiratory pressure support (pressure support plus PEEP) delivered via a face mask in patients who are alert and cooperative at presentation. This approach can supply all the benefits of invasive ventilation to some patient groups while avoiding the adverse effects of intubation and the frequently coadministered sedatives and analgesics. Results from trials in which the investigators compared NIV with conventional oxygen therapy in patients with acute exacerbations of COPD have shown a reduction in intubation rate and inhospital mortality (choice A is incorrect).

Results from trials in patients presenting acutely with cardiogenic pulmonary edema have shown a reduction in intubation rate, especially in patients with hypercapnia (choice C is incorrect).

NIV has also been studied as a technique for early extubation of patients after their initial intubation for respiratory failure; in this setting, benefits, including reduction in duration of intubation and decreased rates of reintubation, have been observed for patients whose respiratory failure was caused by underlying COPD (choice D is incorrect).

By contrast, benefits of NIV have not been readily demonstrable in patients with acute hypoxemic respiratory failure, especially when gas exchange is severely impaired, defined as PaO2/ FiO2 ratio less than 150. Results from several trials have shown no reduction in intubation rates and some dangers when NIV is used in this setting, because forestalling intubation in some patients may reduce physiologic reserve and promote deterioration when intubation is required. Accordingly, additional methods of noninvasive support are under study. A high-flow nasal cannula provides 30 to 80 L/min of humidified oxygen-enriched gas via nasal cannula. This high flow likely increases effective FiO2, creates small amounts of nonadjustable PEEP, and reduces the work of breathing by washing out anatomic dead space and permitting a reduced minute ventilation to achieve the same alveolar ventilation. Another technique under investigation is the use of a helmet interface with NIV to achieve higher PEEP levels and better tolerance of high inspiratory pressures in patients with acute hypoxemic respiratory failure. Both of these methods have shown promise in patients with acute hypoxemic respiratory failure, particularly those with mild to moderate disease and with risk factors for intubation, including obesity.1

Footnotes

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