What term is also known as PEEP and is usually zero unless set, increasing functional residual capacity when applied?

• A. Baseline Pressure
• B. Time Constants
• C. Elastance
• D. Compliance

Answer: (A)

PEEP is the pressure kept in the airways at the end of expiration, creating a baseline airway pressure above atmospheric pressure. This baseline pressure is usually zero unless the clinician sets a PEEP level, and applying it increases functional residual capacity by keeping alveoli open at end expiration, preventing collapse. The term that describes this baseline end-expiratory pressure is Baseline Pressure. Time constants describe how quickly the lungs fill and empty (related to resistance and compliance), elastance is the stiffness of the lung, and compliance measures how easily the lungs expand—none of these name the end-expiratory baseline pressure used in ventilation.