What immediate action should you take for a four-year-old patient with a completely obstructed airway due to a marble?

In the case of a four-year-old with a completely obstructed airway, performing abdominal thrusts is the recommended immediate action. This technique, often referred to as the Heimlich maneuver, is specifically designed to create pressure in the abdominal cavity that can help expel an object lodged in the airway, thus restoring normal breathing.

For a child in this situation, initiating abdominal thrusts can effectively generate the necessary force to dislodge the obstruction, like the marble described. It's crucial to act swiftly, as a complete obstruction can lead to critical situations where the child is unable to breathe or lose consciousness.

Other actions, such as finger sweeps or administering rescue breaths, are not appropriate in this scenario. A finger sweep can potentially push the object further down the airway rather than dislodging it. Administering rescue breaths would be ineffective, as the airway is completely obstructed, preventing air from entering the lungs. Encouraging the child to cough might also be futile since they typically would not be able to generate an effective cough due to the obstruction. Therefore, abdominal thrusts are the most effective response to relieve a complete airway obstruction in this instance.