Final answer:
A decrease in pressure with mechanical ventilation would be indicated by a decrease in lung compliance.
Step-by-step explanation:
When comparing the given options, a decrease in pressure with mechanical ventilation would be indicated by a decrease in lung compliance. Compliance is a measure of how elastic the lung is, and a decrease in lung compliance means that the lungs become stiffer and less pliable. This can be caused by restrictive diseases like fibrosis. When lung compliance decreases, the airways stiffen and collapse upon exhalation, making breathing more difficult. In contrast, an increase in compliance would make it easier for air to flow through the airways and would not indicate a decrease in pressure with mechanical ventilation.