What technique can be used to open the airway of an unresponsive casualty?

The head-tilt, chin-lift maneuver is the correct technique for opening the airway of an unresponsive casualty. This method involves tilting the casualty's head back slightly and lifting the chin upwards. This position helps to reposition the tongue and clear the airway by preventing it from obstructing the throat, thereby allowing for better air passage and ventilation.

This technique is particularly effective because it is simple to perform and does not require any special equipment. It is crucial in emergency situations where breathing is compromised, as it can quickly help restore airflow to the lungs without causing additional injury.

Other techniques such as a finger sweep, which is used to remove visible obstructions from the mouth, and the Heimlich maneuver, which is designed to clear an obstruction in the airway when a person is conscious, are not appropriate for an unresponsive casualty. Similarly, the jaw thrust maneuver is another valid technique often used for suspected spinal injuries, but it may not be as universally applicable as the head-tilt, chin-lift in general situations where rapid airway management is necessary.