What is PEEP and why is it significant?

PEEP, or Positive End-Expiratory Pressure, refers to the pressure remaining in the airways at the end of expiration, which is above atmospheric pressure. This concept is essential in mechanical ventilation as it helps maintain a baseline pressure in the lungs, preventing alveolar collapse or atelectasis. By keeping the alveoli open, PEEP enhances oxygenation and improves overall lung mechanics.

In more detail, PEEP increases functional residual capacity (FRC), thereby increasing the surface area available for gas exchange. This is particularly beneficial for patients with conditions like Acute Respiratory Distress Syndrome (ARDS), where alveolar collapse can significantly impair oxygenation. By applying PEEP, clinicians can improve patient outcomes by optimizing lung recruitment and improving ventilation-perfusion matching.

The other options do not accurately describe PEEP. The pressure at the start of expiration, initial pressure during inhalation, and peak pressure in lung inflation represent different aspects of respiratory mechanics but do not capture the essence of PEEP as a pressure that holds the alveoli open at the end of expiration.