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O2 Toxicity FiO2 >0.6 — FRCA Primary MCQ

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ModeratePhysiology - RespiratoryO2 Toxicity FiO2 >0.6FRCA Primary

Oxygen toxicity affecting the lungs (Lorraine Smith effect) occurs at FiO2 above:

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Correct answer: A — 0.6

Pulmonary oxygen toxicity occurs with prolonged exposure to FiO2 >0.6 (some sources >0.5). Reactive oxygen species damage alveolar epithelium causing: tracheobronchitis / absorption atelectasis / reduced mucociliary clearance / and eventually ARDS-like changes. CNS oxygen toxicity (Paul Bert effect) occurs at hyperbaric pressures and causes seizures.

Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist