To help prevent inflated alveoli from collapsing and reexpanding with each breath, the PEEP level should be set at which point on the deflation part of the loop?

• A. Below the lower inflection point
• B. At the middle of deflation
• C. Above the lower inflection point
• D. At the upper inflection point

Answer: (C)

Keeping PEEP above the lower inflection point on the deflation limb ensures end-expiratory lung volume stays above the closing pressure of most alveoli. When pressure falls during expiration, alveoli tend to derecruit and collapse if PEEP is too low. Setting PEEP above this point keeps those units recruited at end expiration, so they don’t collapse and have to re-open with every breath. Setting it too high risks overdistension (near the upper inflection point), which isn’t necessary for preventing collapse. So, the best approach is to set PEEP above the lower inflection point.