In which situation is NIV most likely to be unsuccessful?

Noninvasive ventilation (NIV) is a supportive therapy designed for patients who experience respiratory distress but still retain some ability to breathe independently. However, in scenarios where severe respiratory distress is present, the likelihood of NIV being unsuccessful increases significantly, primarily due to the patient's compromised ability to maintain adequate ventilation and oxygenation.

In cases of severe respiratory distress, patients may have altered mental status, increased work of breathing, or require immediate intervention to secure their airway. Such conditions may be beyond the capabilities of NIV, as the device cannot provide the level of airway protection and ventilation that endotracheal intubation offers. Intubation is often necessary to secure the airway and ensure that the patient can receive adequate respiratory support without the risks associated with using NIV in such critical circumstances.

On the other hand, situations like self-breathing effectively or using NIV for routine outpatient procedures typically indicate that the patient's respiratory condition is stable enough for NIV to be effective. Using NIV as a preventative measure in asymptomatic patients also leans towards success, as there are no critical impairments to manage, allowing for a more controlled application of therapy without immediate risk of failure.