During injection of contrast for CT simulation, your patient complains of difficulty breathing and feeling faint. He is likely experiencing:

The patient’s symptoms of difficulty breathing and feeling faint following the injection of contrast material point to a potential allergic or anaphylactic reaction. Anaphylaxis can occur as a response to contrast agents, and it typically presents with various symptoms including respiratory distress, swelling, rapid heartbeat, and in some cases, dizziness or fainting due to decreased blood pressure.

In this context, moderate symptoms of anaphylactic shock are characterized by significant respiratory issues, which align with the patient’s report of breathing difficulty. This condition requires immediate medical attention since it can escalate rapidly to more severe life-threatening symptoms.

The other options do not adequately explain the patient's acute presentation. Minor symptoms of respiratory distress may not lead to faintness and usually involve less severity. Symptoms of depression are unrelated to the physiological response to contrast agents and do not encapsulate the respiratory symptoms described here. Claustrophobia typically pertains to anxiety related to confined spaces and does not present with physical symptoms like difficulty breathing or faintness stemming from an allergic reaction. Therefore, the symptoms the patient is experiencing are best aligned with moderate symptoms of anaphylactic shock.