A middle-aged male has had his arm caught in a machine and is holding a towel on a severely injured arm. What should be your first action?

In a scenario where a middle-aged male has sustained a severe arm injury and is showing signs of distress, the most critical first step is to ensure that he receives adequate oxygen to support his breathing and circulation. Administering oxygen through a nonrebreather mask is appropriate if the patient shows signs of shock, difficulty breathing, or altered mental status. This intervention prioritizes stabilizing the patient by providing high-flow oxygen, which can help mitigate the effects of hypoxia and improve oxygenation to vital organs.

While assessing the injury in detail is important, it should not be the first action without ensuring that the patient's airway, breathing, and circulation are stable. Starting CPR is only necessary if the patient is unresponsive and not breathing, which is not indicated in this scenario. Applying a tourniquet might be a consideration for severe bleeding, but it is typically done after a quick assessment of the situation, especially regarding the patient's overall condition and whether there is active bleeding threatening life.

Therefore, the prioritization of oxygen delivery reflects the fundamental principles of trauma care: ensuring the patient’s immediate needs are met to prevent deterioration before further assessments or interventions are performed.