In which scenario should a non-rebreather mask (NRM) be utilized?

A non-rebreather mask (NRM) is specifically designed to deliver a high concentration of oxygen to patients who are experiencing significant respiratory distress, such as those suffering from severe trauma or acute respiratory failure. This device allows for efficient oxygenation, providing close to 100% oxygen flow which is crucial in emergencies where patients cannot adequately oxygenate on their own.

The construction of the NRM includes a reservoir bag that collects oxygen, and one-way valves prevent the patient from re-breathing exhaled carbon dioxide. In the case of severe trauma or pronounced respiratory distress, where the oxygen demand exceeds the supply, the NRM allows first responders to temporarily alleviate hypoxemia, thereby improving the patient's condition as they await further medical interventions.

The other scenarios provided are less suitable for NRM use; for example, mild allergic reactions do not typically require such high levels of oxygen, nor do stable patients who are already maintaining their oxygen levels effectively. Moreover, long-term oxygen therapy generally requires different forms of delivery systems, such as nasal cannulas or other devices specifically designed for chronic care.