What should you do after performing back blows and chest thrusts without success?

In the context of a patient experiencing a severe airway obstruction, if back blows and chest thrusts have been performed without success, the next logical step is to begin CPR cycles. This is due to the fact that the obstruction could lead to a lack of oxygenation, and performing CPR can help restore blood flow and oxygenation to vital organs until the airway is cleared or further medical help is available.

Continuing with CPR involves giving high-quality chest compressions to maintain circulation, which is critical in this emergency situation. It's important to note that, while ideally, the first response to an unresponsive patient with a suspected airway blockage includes the use of back blows and chest thrusts, if those maneuvers are ineffective, transitioning to CPR allows the rescuer to continue attempting to preserve life and sustain vital functions.

The other options, such as checking vital signs, calling for additional help, or using an AED, are less immediate actions that do not directly address the urgent need for circulation and oxygenation when the patient is unresponsive and not breathing. They may be appropriate later, but the priority in this scenario is to initiate CPR without delay.