Final answer:
Choking on a foreign object is the most common cause of airway obstruction in an unresponsive person, leading to partial or complete blocking of the airway and preventing oxygen from entering the lungs.
Step-by-step explanation:
The most common cause of airway obstruction in an unresponsive person is choking due to the respiratory tract being blocked by a foreign object. This can happen when food or other small objects get lodged in the pharynx or trachea, leading to complete or partial obstruction of the air supply.
When the airway is blocked, it prevents oxygen from reaching the lungs and the brain, which can quickly lead to unconsciousness and potentially be fatal. Young children are particularly at risk because they often place objects in their mouths, but adults can also choke on food items that can conform to the shape of the throat.
It's important to recognize the signs of choking: inability to speak, labored breathing with gasping or wheezing, and eventually, cyanosis (blueness) of the face caused by oxygen deprivation. Immediate action, such as performing the Heimlich maneuver.