Final answer:
Resistance-to-breathing indicators are monitored by observing the labor of a firefighter's breathing, and increased resistance can be detected via diagnostic tests like spirometry.
Step-by-step explanation:
The APR effectiveness clue that is monitored by being aware of how labored a firefighter's breathing is referred to as resistance-to-breathing-indicators. A firefighter's increased respiratory effort can suggest increased resistance within their lungs. This resistance can be due to a reduction in airway diameter, causing more collisions between the air molecules and the walls, leading to difficult breathing. Detecting changes in resistance can be achieved through diagnostic tests like spirometry, which measures the rate of air flow in and out of the lungs to diagnose restrictive diseases.