In which of the following scenarios is it safe to use an AED?

Using an AED on a pregnant patient with careful electrode placement is appropriate and safe because the primary concern when using an AED is to ensure that the electrical shock is delivered effectively to the heart. The presence of pregnancy does not contraindicate the use of an AED, as it can be crucial in restoring a normal rhythm in cases of cardiac arrest. Careful electrode placement is important to minimize any potential risk to the fetus while still providing life-saving treatment to the mother.

In contrast, using an AED on a patient experiencing cardiac arrest due to drowning would generally be acceptable; however, it is crucial to ensure that the patient is fully dry before applying the AED pads to prevent electrical injury. Using an AED on a patient lying on a metal surface without precautions poses a risk for grounding, which could lead to ineffective defibrillation or harm to rescuers. Finally, using an AED on a responsive patient is not appropriate since the device is designed for those who are unresponsive and not breathing. The goal of AED use is to assist individuals in cardiac arrest, not those who are conscious and maintaining their own circulation.