Which organisms utilize a one-way air flow through their lungs to maximize airflow efficiency and oxygen consumption?

The answer is birds.

Birds utilize a one-way airflow through their lungs to maximize airflow efficiency and oxygen consumption. Although they inhale and exhale through one trachea, air flows in one direction through birds lungs. This is enabled thanks to air sacks. When birds inhale, air travels through the trachea, which further divides into two bronchi. The part of the air enters the lungs, and the other part remains in posterior air sacks. After the first exhalation, the fresh air from the posterior air sacks enters the lung and displace the spent air which is moved to the trachea. In case there is fresh air in the trachea, spent air is moved to anterior air sacks and after following exhale, it flows out from the trachea.