Under which condition is PEEP primarily indicated for use?

The use of Positive End-Expiratory Pressure (PEEP) is primarily indicated for recruiting dysfunctional alveoli when the partial pressure of arterial oxygen (PaO2) is low. This technique helps to maintain alveolar recruitment and improve ventilation-perfusion matching, thus enhancing oxygenation. In conditions such as Acute Respiratory Distress Syndrome (ARDS) or other forms of restrictive lung disease, there are often collapsed or poorly ventilated areas of the lung that can benefit from the application of PEEP. By preventing the alveoli from fully collapsing at the end of expiration, PEEP increases the surface area available for gas exchange, which can lead to improved PaO2 levels.

Using PEEP in this manner not only helps to enhance oxygenation but can also reduce the need for high fractions of inspired oxygen (FiO2), as it allows more effective use of the lung and can protect against oxygen toxicity when high levels of oxygen are required. Thus, it addresses the fundamental issue of impaired oxygenation in patients experiencing significant respiratory distress.