Final answer:
An increase in airway resistance on a pressure volume loop is indicated by a greater effort required to maintain airflow due to a constricted airway, often as a result of conditions such as an allergic reaction.
Step-by-step explanation:
The changes on the pressure volume loop that indicate an increase in airway resistance can be seen as greater effort required to achieve the same level of airflow. The size of the airway is the primary factor affecting resistance; when airway resistance is increased, it means air has a more difficult time flowing through the constricted airways. According to the relationship F = ΔP/R (where ΔP is the change in pressure, R is the resistance, and F is the flow of air), if R increases, then for a given ΔP, the flow, F, decreases.
An allergic reaction causing the airways to swell will lead to an increase in resistance because the swollen airways allow for less space for air to flow through. The physiological dead space may increase as well due to obstructed airways not allowing proper airflow to certain alveoli. During inhalation, the increased resistance will require the pressure gradient (ΔP) to be higher to maintain airflow, reflecting a steeper slope on the pressure volume loop.