Which of the following may prevent an AED from completing its analysis?

The correct answer is that excessive movement of the patient may prevent an AED from completing its analysis. An automated external defibrillator (AED) analyzes the patient's heart rhythm to determine if a shock is needed. If the patient is moving excessively, it can distort the readings and cause the AED to fail in accurately assessing the heart's rhythm.

Movement can introduce artifacts in the ECG (electrocardiogram) signal, leading to incorrect interpretations. For this reason, it’s crucial to keep the patient as still as possible during the analysis phase of using an AED to ensure accurate readings are obtained.

While factors like radio frequency interference, giving rescue breaths during analysis, and vehicle motion can have varying degrees of impact on AED function, the most direct influence on the analysis phase comes from the patient's movement. It's essential to ensure a stable environment for the AED to function correctly.