hyperoxia

Hyperoxia is a state in which body tissues receive more oxygen than normal, usually due to exposure to inspired oxygen fractions above atmospheric air. In medicine it is defined by elevated PaO2 or by high FiO2, and can be intentional for treatment or incidental during care.

High oxygen levels increase dissolved oxygen in plasma and drive production of reactive oxygen species, causing oxidative stress and tissue injury at the cellular level. In the lungs, high FiO2 can cause absorption atelectasis by washing out nitrogen. Some vascular beds experience vasoconstriction under hyperoxia, which can alter blood flow.

Clinical use: Supplemental oxygen is routinely given to treat hypoxemia and to protect tissues during anesthesia and critical illness. Higher FiO2 is necessary in carbon monoxide poisoning, cyanide poisoning, and certain wound therapies; hyperbaric oxygen therapy uses very high pressures for selected conditions. Neonates require careful oxygen titration to minimize risks such as retinopathy of prematurity.

Risks: Prolonged exposure to high FiO2 or PaO2 raises the risk of pulmonary oxygen toxicity, presenting with cough, dyspnea, and chest pain, and may worsen lung injury in conditions like ARDS. Oxygen can also cause CNS toxicity in extreme settings (rare, e.g., diving or hyperbaric exposure). In COPD, excessive oxygen may worsen CO2 retention.

Management: Use the lowest FiO2 that maintains adequate oxygenation, monitor oxygenation status, and adjust therapy as needed. Avoid unnecessary prolonged exposure to high FiO2, and follow protocols that set target SpO2 values, balancing tissue oxygen delivery with toxicity risk.