What is one primary effect of PEEP on lung function?

One primary effect of Positive End-Expiratory Pressure (PEEP) on lung function is that it increases oxygenation while decreasing the shunt fraction. PEEP works by maintaining airway pressure at the end of expiration, which helps to keep the alveoli open and prevents their collapse. This recruitment of collapsed or under-inflated alveoli enhances gas exchange by increasing the surface area available for oxygen uptake.

By improving ventilation-perfusion matching, PEEP reduces the shunt fraction, which is the portion of blood that returns to the left atrium without participating in gas exchange. An improved shunt fraction means more blood is effectively oxygenated, which leads to improved oxygen levels in the bloodstream, enhancing overall oxygenation in patients who may be experiencing respiratory failure or conditions such as ARDS (Acute Respiratory Distress Syndrome).

Other options may suggest various changes in lung mechanics or pressures, but the significant contribution of PEEP to enhancing oxygenation and reducing areas of poor gas exchange is crucial in the management of patients on mechanical ventilation.