Which of the following best describes two risks associated with high FiO2 therapy in susceptible patients?

• A. Hypoxemia due to device failure
• B. Dehydration and hypoventilation
• C. Oxygen toxicity (hyperoxia) and CO2 retention in COPD
• D. Hyperbaric oxygen toxicity

Answer: (C)

Giving high concentrations of oxygen can lead to two important risks in people who are especially vulnerable: oxygen toxicity from hyperoxia and CO2 retention in COPD.

Oxygen toxicity occurs when the lungs are exposed to very high inspired oxygen pressures for too long. This can trigger the production of reactive oxygen species that damage lung tissue, causing inflammation, edema, and impaired gas exchange. The danger increases with higher FiO2 and longer exposure, so clinicians aim to use the lowest FiO2 that keeps oxygen saturations in a safe range.

In COPD, raising FiO2 can blunt the patient’s drive to breathe, which relies partly on low oxygen levels. Supplying too much oxygen can reduce this drive, leading to hypoventilation and buildup of CO2 (hypercapnia), with the potential for respiratory acidosis.

Hyperbaric oxygen toxicity and the notion of dehydration or device failure–related hypoxemia describe different scenarios not typical of standard high FiO2 therapy in most patients.