Q: What is 'absorptive atelectasis'?

Answer: Absorptive atelectasis is one of the "not very much desired" consequence of high FiO2. Higher oxygen level in lung causes "washout of alveolar nitrogen" which results in alveolar atelectasis. This is probably due to the fact that oxygen diffuses from alveoli to capillaries at faster rate than it gets replenish by inhaled oxygen. Also, particularly in ARDS patients, surfactant abnormalities helps to superimpose the issue. Treatment is applying recruitment maneuver and application of optimum PEEP, followed by FiO2 to keep PaO2 around 65 mm Hg.

Clinical implication: Do not dial more than required FiO2


Reference: 

Santos C, Ferrer M, Roca J, et al. Pulmonary gas exchange response to oxygen breathing in acute lung injury. Am J Respir Crit Care Med 2000; 161:26.