What effect would increasing PEEP primarily have on a patient during mechanical ventilation?

Increasing PEEP (Positive End-Expiratory Pressure) primarily enhances oxygenation in a patient undergoing mechanical ventilation. This is accomplished by preventing the premature collapse of alveoli at the end of expiration, thereby increasing functional residual capacity (FRC) and improving ventilation-perfusion (V/Q) matching.

When PEEP is elevated, it creates a higher baseline airway pressure that stabilizes the alveoli, allowing for better gas exchange. By increasing the surface area available for diffusion, more oxygen can enter the bloodstream, which can be particularly beneficial in conditions like acute respiratory distress syndrome (ARDS) where alveolar collapse leads to significant hypoxemia.

This mechanism is essential in improving arterial oxygenation and can help reduce shunting and improve overall respiratory function. Thus, enhancing oxygenation is a primary and fundamental effect of increasing PEEP during mechanical ventilation.