CPAP is beneficial when treating ventilation-perfusion mismatch in which lung?

When treating ventilation-perfusion mismatch, CPAP (Continuous Positive Airway Pressure) is particularly beneficial for the non-dependent lung. This is because CPAP helps to increase the functional residual capacity and opens collapsed or poorly ventilated areas of the lung, specifically aiding regions with relatively better ventilation but poorer perfusion.

In conditions like Acute Respiratory Distress Syndrome (ARDS) or pulmonary edema, the distribution of blood flow and air exchange may not be uniform across the lungs. The dependent lung, which is typically the lower lung when a patient is in a supine position, may be subjected to greater perfusion due to gravity but might also be affected by fluid accumulation or atelectasis, leading to impaired gas exchange.

By applying CPAP, the airways are kept open, thereby improving oxygenation in the non-dependent lung, where ventilation may be better, but perfusion may still be suboptimal. This targeted approach aids in redistributing blood flow and enhancing overall gas exchange efficiency, making CPAP a crucial tool in managing ventilation-perfusion mismatch specifically in the non-dependent lung.