What are the three main purposes of PEEP?

The selection of B as the correct answer is based on the physiological roles that Positive End-Expiratory Pressure (PEEP) plays in respiratory management, particularly in mechanically ventilated patients.

One of the fundamental purposes of PEEP is to increase the driving pressure of oxygen from the alveoli into the bloodstream. By maintaining a certain level of pressure in the airways at the end of expiration, PEEP helps to prevent the collapse of alveoli, which enhances the functional residual capacity of the lungs and thereby increases the overall surface area for gas exchange. This is crucial for improving oxygenation since it allows for more oxygen to diffuse into the blood.

Additionally, PEEP can help decrease surface tension in the alveoli, promoting better alveolar stability and preventing atelectasis (collapse of lung segments). When alveoli remain open, this helps in improving ventilation distribution and promotion of effective gas exchange, minimizing shunting where blood bypasses ventilated areas of the lung.

Lastly, by reducing shunting, PEEP optimizes the V/Q (ventilation-perfusion) ratio. This means that areas of the lung that are ventilated also receive an appropriate blood supply, which is critical for improving oxygenation further.

In contrast, the other choices do not accurately