In the evaluation of a casualty's airway, what should be checked first?

When evaluating a casualty's airway, the first step is to check for the presence of any visible obstruction. This is crucial because any obstruction—whether it be blood, vomit, foreign objects, or any other material—can immediately compromise the airway and impede airflow. Identifying and removing visible obstructions can be life-saving and is necessary before assessing other airway-related parameters.

While checking breath sounds, respiratory rate, and level of consciousness are important components of a thorough evaluation, they occur after ensuring that the airway is clear. If there is an obstruction that hasn't been addressed, evaluating these other factors may not provide useful information regarding the casualty's respiratory status or overall condition. Thus, prioritizing the observation of any visible obstruction ensures that the airway is patent and allows for effective subsequent assessments and interventions.