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High fractions of inspired oxygen (FiO2) have been associated specifically with 4 pulmonary consequences. Name them, please.

- increased intrapulmonary right-to-left shunt fraction (d/t absorptive atelectasis)

- diminished lung volumes (d/t absorptive atelectasis)

- accentuation of hypercapnia

- damage to airways and pulmonary parenchyma


Define absorptive atelectasis.

High concentrations of supplemental oxygen cause washout of alveolar nitrogen (ie, oxygen replaces nitrogen in the alveolus).

This may cause absorptive atelectasis if oxygen diffuses from the alveoli to the capillaries faster than it is replenished by inhaled oxygen.


Absorptive atelectasis is theoretically more likely in the following 4 circumstances:

• A low regional ventilation-perfusion ratio, which limits replenishment of alveolar oxygen (in general, airway closure is required for this mechanism to be important)

• Qualitative or quantitative surfactant abnormalities that promote alveolar collapse and further reduce the ventilation-perfusion ratio

• A high rate of oxygen uptake, due to an increased in metabolic demand

• An impaired pattern of respiration that fails to correct atelectasis (eg, ventilation at low tidal volumes and/or without intermittent sighs)


The term oxygen toxicity, is generally refers to what?

parenchymal lung injury d/t supplemental oxygen


Oxygen toxicity is mediated by what?

reactive oxygen species

(which can promote inflammation and induce cell death)


Is there a well-defined threshold FiO2 or duration of supplemental oxygen therapy below which oxygen toxicity cannot occur?



Patients with any previous bleomycin exposure should not receive an FiO2 above ____% without carefully weighing the risks versus the benefits.