Oxygen toxicity: Symptoms

Increasing partial pressure of oxygen in the blood (hyperoxia) leads to increased reactive oxygen intermediates (ROI) – superoxide anion, hydroxyl radical, and hydrogen peroxide. When cellular antioxidant defenses are depleted, these ROI’s can impair cellular function, increase inflammatory response and induce apoptosis. The respiratory system and CNS are particularly susceptible to hyperoxia and produce the most clinically apparent symptoms.

Respiratory symptoms: can manifest after > 12hours of 50% FiO₂ and initially consists of direct damage to respiratory tract mucosa including tracheobronchitis manifested by dry cough and hoarseness. Administration of 100% FiO₂ short term can lead to atelectasis and after longer duration (>24 hours) leads to decreased vital capacity and diffuse alveolar damage.

CNS symptoms: Nausea, facial muscle twitching, tinnitus, irritability, anxiety, dizziness, seizure, visual changes including tunnel vision, myopia, direct retinal damage (Retinopathy of prematurity).