The correct answers are C. Increased tissue damage and E. Coronary artery vasoconstriction.

In patients with acute coronary syndrome (ACS) who are NOT hypoxemic, routine oxygen administration is no longer recommended because it may actually be harmful.

Key pathophysiology:

1. Coronary Artery Vasoconstriction (E):

High concentrations of oxygen can cause vasoconstriction of coronary arteries, which reduces blood flow to already ischemic heart tissue.

“Supplemental oxygen in non-hypoxemic patients may cause coronary vasoconstriction.”

2. Increased Tissue Damage (C):

Excess oxygen can lead to oxidative stress and worsen ischemic injury, potentially increasing infarct size or tissue damage.

“Hyperoxia may increase oxidative injury and worsen myocardial damage.”

Why the other options are incorrect:

A. Reduced mortality: Evidence does not support mortality benefit in non-hypoxemic ACS patients.

B. Resolution of chest pain: Oxygen does not reliably relieve ischemic chest pain unless hypoxia is present.

D. Reduction in infarction size: Studies show no benefit and possible harm.

NREMT/AHA-aligned guidance emphasizes:

“Administer oxygen only if SpO₂ is less than 94% or if the patient is hypoxic.”

Routine oxygen in normoxic patients is not recommended and may be harmful.

Exact Extracts (NREMT/AHA-aligned references):

“Avoid routine oxygen use in patients with normal oxygen saturation.”

“Hyperoxia can cause coronary vasoconstriction.”

“Excess oxygen may worsen myocardial injury.”

Clinical Priority Summary:

In non-hypoxemic ACS patients, oxygen can cause harm rather than benefit, specifically vasoconstriction and increased tissue damage, making C and E correct.