BLS — Basic Life Support — All Questions
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At what rate should chest compressions be delivered to an adult in cardiac arrest?
- a.60 to 80 compressions per minute
- b.80 to 100 compressions per minute
- c.100 to 120 compressions per minute✓
- d.At least 140 compressions per minute
Current AHA guidelines specify a compression rate of 100 to 120 per minute for all ages. Slower than 100 does not generate adequate perfusion, while faster than 120 shortens the recoil phase so the heart cannot refill, which paradoxically lowers the blood delivered per compression.
What is the correct compression depth for an adult victim?
- a.At least 1 inch (2.5 cm)
- b.At least 2 inches (5 cm) but no more than 2.4 inches (6 cm)✓
- c.At least 3 inches (7.5 cm)
- d.As deep as possible with each compression
Adult compressions should be at least 2 inches (5 cm) and not exceed 2.4 inches (6 cm). Depth less than 2 inches fails to move enough blood, while excessive depth beyond 2.4 inches increases the risk of injury to the chest and underlying organs without added benefit.
What is the correct compression depth for an infant (under 1 year)?
- a.About 0.5 inch (1 cm)
- b.About 1 inch (2.5 cm)
- c.About 1.5 inches (4 cm), or one-third the depth of the chest✓
- d.At least 2.4 inches (6 cm)
Compress an infant's chest at least one-third of its anterior-posterior diameter, which is about 1.5 inches (4 cm). For a child it is about one-third the depth, roughly 2 inches (5 cm). Compressing to a fixed fraction of chest depth scales the force appropriately to the small size of the pediatric chest.
To maximize blood flow during CPR, rescuers should allow complete chest recoil and aim for a chest compression fraction of at least:
- a.30%
- b.40%
- c.50%
- d.60%✓
Chest compression fraction — the proportion of arrest time spent actively compressing — should be at least 60%. Allowing full recoil between compressions lets the heart refill, and minimizing pauses (keeping any interruption under 10 seconds) preserves the coronary and cerebral perfusion that compressions build up.