Which condition is associated with PV loop extending to the right?

• A. Pneumonia
• B. Fibrosis
• C. Asthma
• D. ARDS

Answer: (D)

A pressure–volume loop shows how much volume you get for a given airway pressure. If the loop extends farther to the right during inflation, you achieve a larger end-inspiratory volume at the same pressure. This rightward extension reflects recruitable lung units opening up when pressure is applied, increasing the volume you can hold.

In ARDS, the lung is badly heterogeneous with collapsed or fluid-filled regions that can be reopened (recruited) with positive pressure and PEEP. Opening these units adds lung volume at a given pressure, so the PV loop shifts to the right. The other conditions tend to reduce overall compliance or change the pattern of ventilation in ways that don’t produce this same rightward expansion of the inspiratory limb: fibrosis makes the lung stiffer with little recruitable volume, asthma involves airway obstruction with air trapping that alters expiratory flow rather than the inspiratory rightward shift, and pneumonia mainly reduces compliance without the same degree of recruitable units.