Oxygen is given in unstable angina if oxygen saturation is below what value?

• A. 99%
• B. 95%
• C. 90%
• D. 92%

Answer: (B)

The main idea is ensuring adequate oxygen delivery to the ischemic heart. In unstable angina, supplemental oxygen is used to maximize the amount of oxygen that reaches the myocardium, helping to relieve ischemia as long as oxygen saturation is not high enough. The target in this context is to keep SpO2 at or above 95%, so oxygen is given when the saturation falls below that level. Normal values are around the high 90s, so a value like 99% doesn’t require oxygen, while lower readings signal hypoxemia that could worsen myocardial ischemia. The other options (90% or 92%) reflect hypoxemia, but the threshold emphasized here is 95%, which is why 95% is the correct trigger in this question.